Patent Publication Number: US-10314346-B2

Title: Face mask having improved comfort through cooling of microclimate through use of a phase change material

Description:
RELATED APPLICATION 
     The present application is the national phase of and claims priority to PCT/US2017/028481, filed Apr. 20, 2017, which claims priority to U.S. Provisional Application Ser. No. 62/325,729 filed on Apr. 21, 2016, both of which are incorporated herein in their entirety by reference thereto. 
    
    
     BACKGROUND OF THE INVENTION 
     The use of face masks and other personal protective equipment (PPE) such as surgical gowns, surgical drapes, bouffant caps, etc. is a recommended practice in the healthcare industry to help prevent the spread of disease. For instance, face masks worn by healthcare providers help reduce infections in patients by filtering the air exhaled from the wearer thus reducing the number of harmful organisms or other contaminants released into the environment. 
     This is especially important during surgeries where the patient is much more susceptible to infection due to the presence of an open wound site. Similarly, patients with respiratory infections may use face masks to prevent the spread of disease by filtering and containing any expelled germs. Additionally, face masks protect the healthcare worker by filtering airborne contaminants and microorganisms from the inhaled air. 
     Some diseases, such as hepatitis and AIDS, can be spread through contact of infected blood or other body fluids to another person&#39;s mucous membranes (i.e., eyes, nose, mouth, etc.). The healthcare industry recommends specific practices to reduce the likelihood of contact with contaminated body fluids. One such practice is to use face masks, surgical gowns, surgical drapes, bouffant caps, and other similar PPE, which are resistant to penetration from a splash of body fluids. 
     The material used to form such PPE can be comprised of several layers. The layer that is positioned closest to the skin of the wearer is typically referred to as the inner layer. The layer furthest from the skin of the wearer is referred to as the outer layer. An additional layer or layers of material can be disposed between the outer layer and the inner layer. Typically, one of these additional layers is a filtration layer, such as a microfiber fiberglass layer or an electret-treated meltblown layer. 
     As stated, face masks, surgical gowns, surgical drapes, bouffant caps, and other similar PPE may be designed to be resistant to penetration by splashes of fluids so that pathogens found in blood or other fluids are not able to be transferred to skin of the user of such PPE. The American Society of Testing and Materials (ASTM) has developed test method F1862-13, “ Standard Test Method of Resistance of Medical Face Masks to Penetration by Synthetic Blood  ( Horizontal Projection of Fixed Volume at a Known Velocity ” (2013) to assess an article&#39;s ability to resist penetration by a splash at three levels of pressure. This method is referenced in ASTM F2100-11, “ Standard Specification for Performance of Materials Used in Medical Face Masks ” (2011), which specifies a set of performance criteria for medical face masks. To achieve Level 3 performance, which is the most stringent level of testing in ASTM F2100-11, a face mask must resist splashes of 2 milliliters of synthetic blood (available from Johnson, Moen &amp; Co., 2505 Northridge Lane NE, Rochester, Minn. 55906) at 160 mmHg per the ASTM F1862-13 procedure. 
     The splash resistance of an article of PPE (e.g., a face mask, etc.) is typically a function of the ability of the layer or layers of the structure used in the article to resist fluid penetration, and/or their ability to reduce the transfer of the energy of the fluid splash to subsequent layers, and/or their ability to absorb the energy of the splash. Typical approaches to improving splash resistance are to use thicker materials or additional layers in the construction of the structure. However, these solutions may increase the cost of the structure, increase the weight of the structure, reduce the porosity of the structure, and add discomfort to the wearer by negatively impacting the thermal resistance of the multi-layered structure. 
     An additional approach to improving the splash resistance of materials or structures used to form face masks, surgical gowns, surgical drapes, bouffant caps, or other similar PPE is to incorporate a layer of porous, high loft, fibrous material. This type of material is advantageous in that the layer will absorb or dissipate the energy of the impact of the fluid splash. However, it is often the case that fluid will saturate this high loft material, hence reducing its effectiveness in absorbing the energy of a future fluid splash. Additionally, fluid can be squeezed out of this high loft material and may be transferred through subsequent layers upon compression of the multi-layered structure. 
     Moreover, incorporating additional layers of material into the mask can increase the amount of heat contained within the mask&#39;s microclimate, which can cause discomfort to the wearer. Further, the face is very sensitive to changes in temperature, much more so than other places in the body. The cheeks and lips are extremely sensitive. When a person wears a mask, the microclimate inside the mask increases a few degrees due to trapped heat from the person&#39;s breath. Just a few degrees of heat can be very uncomfortable and result in the wearer feeling they mask is unbreathable and can prevent a person from not complying with PPE protocols. 
     As such, a need exists for a fabric and articles formed therefrom (e.g., face masks) having improved fluid resistance but without imparting discomfort to the user. In particular, a need exists for a mask that can cool the microclimate in the dead space of a face mask while at the same time providing enhanced fluid resistance without having to incorporate high loft layers of material into the mask. 
     SUMMARY OF THE INVENTION 
     According to one embodiment, the present invention contemplates a face mask formed from a splash resistant multi-layered structure. The multi-layered structure includes an outer layer of material having an outer-facing surface and an inner-facing surface; an inner layer of material having an outer-facing surface and an inner-facing surface; and a first plurality of three-dimensional spacers disposed on the inner-facing surface of the inner layer of the multi-layered structure, wherein the first plurality of three-dimensional spacers are arranged in a discontinuous pattern, further wherein the first plurality of three-dimensional spacers include an encapsulated phase change material. 
     In one particular embodiment, the encapsulated phase change material can be encapsulated with a binder. 
     In another embodiment, the first plurality of three-dimensional spacers can be arranged on a substrate. The substrate can be a nonwoven material, such as a polyester, a polyolefin, a blend of natural fibers, or a combination thereof. Further, in one embodiment, the substrate can cover about 10% to about 100% of the surface area of the inner-facing surface of the inner layer of the face mask. In another embodiment, the substrate can be disposed in a border around a perimeter of the face mask, and the border can have a width of from about 0.5 millimeters to about 15 millimeters. 
     In yet another embodiment, the face mask can cool a microclimate formed between the inner layer of the face mask and a wearer&#39;s face by a temperature ranging from about 1° C. to about 7° C. after exhalation by the wearer. 
     In an additional embodiment, the phase change material can provide from about 2600 Joules/m 2  of cooling to about 20,000 Joules/m 2  of cooling to the face mask by absorbing heat from exhaled air in an area of dead space in the face mask and by absorbing heat from a user&#39;s skin. 
     In still another embodiment, the phase change material can provide at least about 30 Joules of cooling to the face mask by absorbing heat from exhaled air in an area of dead space in the face mask and by absorbing heat from a user&#39;s skin. 
     In one more embodiment, the face mask can include a second plurality of three-dimensional spacers disposed on a surface located within the multi-layered structure, wherein the second plurality of three-dimensional spacers define a space between the outer layer of material and at least one additional layer of material positioned between the outer layer of material and the inner layer of material, wherein the space spans a distance at least as great as a maximum height of the second plurality of three-dimensional spacers, further wherein the second plurality of three-dimensional spacers aid in absorbing and dispersing the energy associated with a fluid contacting the outer layer of material. 
     Further, the second plurality of three-dimensional spacers can define a plurality of channels for redirecting the flow of fluid that strikes the outer layer of material, wherein the channels have an orientation such that the fluid is directed laterally away from the point of contact of the fluid through the channels. 
     In addition, the second plurality of three-dimensional spacers can be arranged in a continuous or discontinuous pattern. Moreover, when the pattern is a discontinuous pattern, the discontinuous pattern can include a plurality of dots, wherein the dots are arranged on the additional layer of material in a series of columns and a series of rows. 
     In one more embodiment, the second plurality of three-dimensional spacers can include a binder, an ink, an adhesive, or a combination thereof. 
     In yet another embodiment, the second plurality of three-dimensional spacers can further include a functional additive contained within the binder, the ink, the adhesive, of the combination thereof, wherein the functional additive can include a phase change material, a fragrance, an absorbent material, a superabsorbent material, an antimicrobial, a therapeutic agent, a topical ointment, or a combination thereof. Moreover, the functional additive can be present in an amount ranging from about 0.25 wt. % to about 70 wt. % based on the dry weight of the second plurality of three-dimensional spacers present within the multi-layered structure. 
     In one more embodiment, the second plurality of three-dimensional spacers can be disposed on an outer-facing surface of the at least one additional layer of material. 
     In still another embodiment, the at least one additional layer of material can be a spunbond web positioned adjacent the outer layer of material, wherein the multi-layered structure further comprises a meltblown web, wherein the meltblown web is positioned towards the inner layer of material. 
     In yet another embodiment, the outer layer of material can be a spunbond web, the inner layer of material can be a nonwoven polyester, and three additional layers of material can be positioned between the outer layer and the inner layer, wherein a first additional layer of material is a spunbond web positioned adjacent the inner-facing surface of the outer layer, wherein a second additional layer of material is a meltblown web positioned adjacent an inner-facing surface of the first additional layer of material, and wherein a third additional layer of material is a spunbond web positioned between an inner-facing surface of the second additional layer of material and an outer-facing surface of the inner layer of material. 
     In an additional embodiment, the inner layer of material, the outer layer of material, or a combination thereof can include a thermally conductive material, wherein the thermally conductive material reduces the R-value of the inner layer of material, the outer layer of material, or a combination thereof. 
     In another embodiment, a coating comprising a thermally conductive material can be disposed on a surface of the inner layer of material, a surface of the outer layer of material, or a combination thereof, wherein the thermally conductive material reduces the R-value of the inner layer of material, the outer layer of material, or a combination thereof. 
     Further, the thermally conductive material can include metal particles, metal fibers, a metal ink, a thermally conductive polymer, carbon, or a combination thereof. 
     In one more embodiment, the inner layer of material, the outer layer of material, or a combination thereof can include a moisture absorptive material, wherein the moisture absorptive material reduces the R-value of the inner layer of material, the outer layer of material, or a combination thereof. In addition, the moisture absorptive material can include cotton fibers, rayon fibers, surfactant-treated cellulosic fibers, or a combination thereof. 
     The present invention also contemplates a face mask formed from a splash resistant multi-layered structure. The multi-layered structure includes an outer layer of material having an outer-facing surface and an inner-facing surface; an inner layer of material having an outer-facing surface and an inner-facing surface; and a plurality of three-dimensional spacers disposed throughout the inner layer of the multi-layered structure, where a first portion of each of the plurality of three-dimensional spacers are disposed on the outer-facing surface of the inner layer, wherein a second portion of each of the plurality of three-dimensional spacers are disposed on the inner-facing surface of the inner layer, and wherein a third portion of each of the plurality of three-dimensional spacers extend through the inner layer as channels that provide a continuous path between the first portion and the second portion of each of the plurality of three-dimensional spacers, further wherein the plurality of three-dimensional spacers include an encapsulated phase change material. 
     In one particular embodiment, the plurality of three-dimensional spacers can be arranged in a discontinuous pattern. 
     In another embodiment, the second portion of each of the plurality of three-dimensional spacers can contact a smaller surface area of the inner-facing surface compared to a surface area of the outer-facing surface contacted by the third portion of each of the plurality of three-dimensional spacers. 
     The present invention also contemplates a face mask formed from a splash resistant multi-layered structure, where the multi-layered structure includes an outer layer of material having an outer-facing surface and an inner-facing surface; an inner layer of material having an outer-facing surface and an inner-facing surface; and a plurality of three-dimensional spacers disposed on the inner-facing surface of the inner layer of the multi-layered structure, wherein the plurality of three-dimensional spacers are arranged in a discontinuous pattern, further wherein the plurality of three-dimensional spacers include an encapsulated phase change material, wherein the encapsulated phase change material provides from about 2600 Joules/m 2  of cooling to about 20,000 Joules/m 2  of cooling to the face mask. 
     The present invention also contemplates a face mask formed from a splash resistant multi-layered structure, where the multi-layered structure includes an outer layer of material having an outer-facing surface and an inner-facing surface; an inner layer of material having an outer-facing surface and an inner-facing surface; and a plurality of three-dimensional spacers disposed on the inner-facing surface of the inner layer of the multi-layered structure, wherein the plurality of three-dimensional spacers are arranged in a discontinuous pattern, further wherein the plurality of three-dimensional spacers include an encapsulated phase change material, wherein the encapsulated phase change material provides at least about 30 Joules of cooling to the face mask. 
     These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof to one skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which: 
         FIG. 1  is a perspective view of a face mask having a body portion that can be formed from a multi-layered structure contemplated by the present invention; 
         FIG. 2  is a perspective view of a face mask with a body portion where the face mask is attached to the head of a user; 
         FIG. 3  is a front view of a surgical gown that can be formed from the multi-layered structure contemplated by the present invention; 
         FIG. 4  is a perspective view of a layer of material that can be used in the multi-layered structure of the present invention, where a plurality of three-dimensional spacers has been applied to a surface of the material; 
         FIG. 5  is a cross-sectional view of two layers of the multi-layered structure of the present invention prior to an insult of a bodily fluid, such as blood, at an outer-facing surface of the multi-layered structure; 
         FIG. 6  is a cross-sectional view of two layers of the multi-layered structure of the present invention during an insult of a bodily fluid, such as blood, at an outer-facing surface of the multi-layered structure; 
         FIG. 7  is a cross-sectional view of a multi-layered structure that does not contain the three-dimensional spacers contemplated by the present invention; 
         FIG. 8  is a cross-sectional view of an exemplary multi-layered structure that contains three-dimensional spacers applied to one of the layers of the multi-layered structure according to one embodiment of the present invention; 
         FIG. 9  is a cross-sectional view of an exemplary multi-layered structure that contains three-dimensional spacers applied to one of the layers of the multi-layered structure according to another embodiment of the present invention; 
         FIG. 10  is a cross-sectional view of an exemplary multi-layered structure that contains three-dimensional spacers applied to two of the layers of the multi-layered structure according to still another embodiment of the present invention; 
         FIG. 11  is a cross-sectional view of an exemplary multi-layered structure that contains three-dimensional spacers applied to two of the layers of the multi-layered structure according to one embodiment of the present invention; 
         FIG. 12  is a cross-sectional view of an exemplary multi-layered structure that contains three-dimensional spacers applied to two of the layers of the multi-layered structure according to one embodiment of the present invention; 
         FIG. 13  is a top view of an inner-facing surface of face mask according to one embodiment of the present invention where three-dimensional spacers in the form of an encapsulated phase change material (e.g., an encapsulated phase change material mixed with a binder) are arranged on a nonwoven layer that is applied as a border and in a middle portion of an inner-facing surface of the face mask; 
         FIG. 14  is a cross-sectional view of the face mask of  FIG. 13 ; 
         FIG. 15  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing the control face mask of Example 1, where no phase change material is present on the face mask; 
         FIG. 16  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a pleated face mask, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  around the perimeter of the face mask and a rectangular section of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  in the center of the mask, where the nonwoven material with the encapsulated phase change material covers 30% of the surface area of the mask, resulting in a mask that includes about 100 Joules of phase change material; 
         FIG. 17  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing an pleated face mask as, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  around the perimeter of the face mask and an oval section of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  in the center of the mask, where the nonwoven material with the encapsulated phase change material covers 30% of the surface area of the mask, resulting in a mask that includes about 100 Joules of phase change material; 
         FIG. 18  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing the control face mask of Example 2, where no phase change material is present on the face mask; 
         FIG. 19  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  around the perimeter of the face mask; 
         FIG. 20  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  around the perimeter of the face mask, where the border is in the form a nonwoven layer, where each layer includes a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2 ; 
         FIG. 21  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 16,000 Joules/m 2  around the perimeter of the face mask; 
         FIG. 22  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  around the perimeter of the face mask as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 30% of the surface area of the mask; 
         FIG. 23  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  around the perimeter of the face mask, where the border is in the form of two nonwoven layers, where each layer includes a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  phase change material, as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the material is in the form of two nonwoven layers, where each layer includes a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  phase change material, where the nonwoven material with the encapsulated phase change material covers 30% of the surface area of the mask; 
         FIG. 24  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 16,000 Joules/m 2  around the perimeter of the face mask as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 16,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 30% of the surface area of the mask; 
         FIG. 25  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 16,000 Joules/m 2  around the perimeter of the face mask as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the material is in the form of two nonwoven layers, where each layer includes a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  phase change material, where the nonwoven material with the encapsulated phase change material covers 30% of the surface area of the mask; 
         FIG. 26  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 16,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 30% of the surface area of the mask; 
         FIG. 27  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  around the perimeter of the face mask as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 30% of the surface area of the mask, where the nonwoven material is in the form of a single layer; 
         FIG. 28  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 30% of the surface area of the mask, where the face mask had an inner-facing layer having at total surface area of about 0.023 m 2 , which is about 30% less than the total surface area of the inner-facing layers of the pleated face masks tested in  FIGS. 18-27, 30-34, and 36-40 , which have a total surface area of about 0.032 m 2 ; 
         FIG. 29  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a nonwoven material containing a strip of foam containing encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  positioned across a top portion of the inner-facing surface of the face mask, as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 30% of the surface area of the mask, where the face mask had an inner-facing layer having a total surface area of about 0.0305 m 2 ; 
         FIG. 30  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 40 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  around the perimeter of the face mask as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 60% of the surface area of the mask; 
         FIG. 31  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  around the perimeter of the face mask as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 60% of the surface area of the mask; 
         FIG. 32  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 16,000 Joules/m 2  around the perimeter of the face mask as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 16,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 60% of the surface area of the mask; 
         FIG. 33  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 16,000 Joules/m 2  around the perimeter of the face mask as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 60% of the surface area of the mask; 
         FIG. 34  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 16,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 60% of the surface area of the mask; 
         FIG. 35  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 40 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 60% of the surface area of the mask, where the face mask had an inner-facing layer having a total surface area of about 0.023 m 2 ; 
         FIG. 36  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  around the perimeter of the face mask as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 100% of the surface area of the mask; 
         FIG. 37  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  around the perimeter of the face mask as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 100% of the surface area of the mask; 
         FIG. 38  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 16,000 Joules/m 2  around the perimeter of the face mask as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 16,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 100% of the surface area of the mask; 
         FIG. 39  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 16,000 Joules/m 2  around the perimeter of the face mask as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 100% of the surface area of the mask; 
         FIG. 40  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 16,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 100% of the surface area of the mask; 
         FIG. 41  is a cross-sectional view of an exemplary multi-layered structure that contains three-dimensional spacers that can be in the form of an encapsulated phase change material applied to two of the layers of the multi-layers structure according to another embodiment of the present invention, where inner layer of the face mask includes phase change material on both its skin-facing surface and its exterior-facing surface, where the phase change material is also present in channels passing through the inner layer of the face mask; and 
         FIG. 42  is a top view of an inner-facing surface of face mask according to one embodiment of the present invention where three-dimensional spacers in the form of an encapsulated phase change material (e.g., an encapsulated phase change material mixed with a binder) are arranged on a nonwoven layer that is applied as two rectangular strips on an inner-facing surface of the face mask. 
     
    
    
     Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present invention. 
     DETAILED DESCRIPTION 
     Reference now will be made in detail to various embodiments of the invention, one or more examples of which are set forth below. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations may be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment, may be used on another embodiment to yield a still further embodiment. For the purposes of this application, like features will be represented by like numbers between the figures. 
     Generally speaking, the present invention is directed to a face mask or any other article where a cool microclimate and splash resistance are desired, where the article is formed from a multi-layered structure that includes one or more layers of material coated with discontinuous patterns, dots, strips, etc. of phase change material, which are incorporated into the face mask construction to provide for cooling of the microclimate in the dead space of the face mask. Optimized cooling is achieved by strategic placement of layers coated with a phase change material within the mask construction and the amount and density of the phase change material in contact with the temperature sensitive areas of the face, as well as areas experiencing the maximum amount of thermal flux from respiration. The shape of the mask can also be adjusted to increase the area of skin in contact with the phase change material and to decrease the volume of the dead space. The latter reduces the volume of warm, trapped exhaled air which enables the use of less phase change material to affect a sensible amount of cooling. The discontinuous patterns of phase change material also provide separation between the layers of the mask which can improve splash resistance. 
     Layers of materials coated with phase change material (e.g., a microencapsulated paraffin wax) can be incorporated into the face mask construction to provide cooling of the microclimate in the dead space of the face mask. The transition temperature of the phase change material can be selected to provide cooling in a microclimate adjacent a mask wearer&#39;s skin, where the transition temperature can range from about 25° C. to about 29° C., such as from about 26° C. to about 28° C. in order to melt upon exhalation by the wearer, where the microclimate can reach temperatures as high as about 95° C. During exhalation, the melting of the phase change material absorbs energy from the warm air thereby reducing the temperature rise in the microclimate. During inhalation, the phase change material re-solidifies as it releases energy back to the cooler ambient air, such as at a temperature ranging from about 20° C. to about 23° C., such as from about 21° C. to about 22° C. The phase change material is then available to remelt when the user exhales again and the microclimate temperature increases. The use of discontinuous patterns of phase change material also provides inter-layer spacing between the layers of the mask which can improve splash resistance. The discontinuous patterns can be in the shape of dots, logos, grids, stripes, etc. The phase change material absorbs energy from exhaled breath and heat from facial skin to generate cooling which provides user comfort while wearing mask. Cooling for skin contact and microclimate air temperature is optimized by adjusting factors such as which type and/or layer of material in the sandwich of face mask construction includes the phase change materials; the location of the phase change material on the particular layers; the energy capacity of the phase change material (i.e., the amount of phase change material applied); and the temperature at which the phase change material transitions between a solid and a liquid. 
     Variations of placement and amount of phase change material within the mask structure and at specific locations on the face were tested to measure the impact of phase change material placement on user preference. The overall design of the mask can play a crucial role in the amount of phase change material needed for effective cooling. By increasing the area of phase change material in direct contact with facial skin and by decreasing the volume of the dead space, and thus the amount of warm, trapped exhaled air, the amount of phase change material necessary for sufficient cooling to provide user comfort is decreased. 
     As a result of the particular pattern, surface area coverage, and latent heat of fusion of the encapsulated phase change material (e.g., a microencapsulated paraffin wax) present on an inner surface of the face masks of the present invention, the microclimate in the dead space of the face mask can be reduced by an amount ranging from about 1° C. to about 7° C., such as from about 1.3° C. to about 6° C., such as from about 1.5° C. to about 5° C. contemplated. For instance, based on the surface area of the mask, the microclimate in the dead space of the face mask can be reduced by from about 25° C./m 2  to about 225° C./m 2 , such as from about 40° C./m 2  to about 200° C./m 2 , such as from about 50° C./m 2  to about 150° C./m 2 . 
     The present invention can also improve the splash resistance of an article, such as a face mask. The splash resistance of the face mask is facilitated by a state of forced separation between adjacent layers of the multi-layered structure, such as between an inner-facing surface (i.e., a layer that faces towards the skin of a user) of a first layer of material and an outer-facing surface (i.e., a layer that faces away from the skin of a user) of a second layer of material. The forced separation between the two adjacent layers of material is the result of the presence of a plurality of three-dimensional spacers positioned between the adjacent layers of the multi-layered structure, where the plurality of three-dimensional spacers can be positioned on one or both of the adjacent layers of material such that a distance at least as large as the maximum height of the plurality of three-dimensional spacers separates the two layers from each other. The three-dimensional spacers can be present on a layer of material in a continuous or discontinuous pattern or can be present on a layer of material in a random fashion. As a result of the plurality of three-dimensional spacers present between two layers of the multi-layered structure, a plurality of channels can be formed between the layers to increase the interlayer spacing so that the splash resistance and fluid barrier capabilities of the multi-layered structure can be enhanced by facilitating the lateral spread of fluid once the fluid contacts the multi-layered structure. Further, the stiffness provided by the three-dimensional spacers can facilitate the lateral dissipation of energy to prevent compression of the layers of the multi-layered structure when a fluid insult occurs. Such an arrangement prevents fluid from penetrating through the entire multi-layered structure, which could endanger the health of the user when the multi-layered structure is formed into PPE. Moreover, the presence of the three-dimensional spacers can reduce the number of layers of material required to form a multi-layered structure having sufficient splash resistance. Likewise, the presence of the three-dimensional spacers can enable the use of materials with lower basis weights to form a PPE article, which can increase the comfort of the user. Specifically, the reduction in basis weight or elimination of one or more layers of the material can reduce thermal resistance, lower the pressure drop across the layers of the multi-layered structure, and reduce the overall weight of the multi-layered structure to enhance breathability and comfort. 
     Alternatively and/or additionally, it is contemplated that the filter material component or filtration layer of the multi-layered structure may be modified to take advantage of the splash resistance and fluid barrier capabilities of the multi-layered structure. Meltblown fabrics (and/or other filtration media) used in conventional multi-layered structures for articles such as face masks are selected to provide greater resistance to penetration by liquids as part of the multi-layered structure. As a result, the meltblown fabrics (and/or other filtration media) may have unnecessarily high basis weights and/or unnecessarily high levels of pressure drop. According to an aspect of the present invention, the advantageous splash resistance and fluid barrier capabilities of the multi-layered structure enable use of meltblown fabrics (and/or other filtration media) having lower basis weights and/or lower levels of pressure drop. Moreover, the greater “breathability” of the meltblown fabrics (and/or other filtration media) provides more efficient energy transfer between phase change material and air exchanged during a respiration cycle. This is believed to be significant at least because it allows for the economical and efficient use of phase change material in an article such as a face mask. As a result, less phase change material may be needed to accomplish a threshold level of energy transfer, which important because it reduces the amount of an expensive component in a disposable article and can have a very large impact on the commercial viability of such disposable articles. The modification is also significant because it enables the manufacture of practical and economical face masks having a smaller face mask area while maintaining or even increasing filtration efficiency, protection, and/or user comfort. As a result of using less or fewer materials and/or decreasing mask size, one can reduce the cost of a disposable article which can have a very large impact on the commercial viability of such disposable articles. Additionally, the meltblown fabrics used in the face mask of the present invention can have increased porosity to promote more efficient refreezing of the phase change material during periods of inhalation when the cold air from, for instance, an operating room is pulled across the construction of the face mask to refreeze the melted phase change material that has been melted by the heat in exhaled breath and facial skin. Specifically, the breathing resistance of the meltblown fabrics contemplated by the present invention can be less than about 5 millimeters of H 2 O. For instance, for improved recycling of the phase change material, the breathing resistance of the meltblown fabrics can be less than about 2 millimeters of H 2 O, such as less than about 1 millimeter H 2 O, where the unit millimeter of water (mm H 2 O) is defined as the pressure exerted at the base of a column of fluid exactly 1 millimeter (mm) high, and the fluid density is exactly 1.004514556 gram per cubic centimeter (g/cm 3 ), at a physical location where the gravity acceleration is exactly 9.80665 m/sec 2 . 
       FIGS. 1 and 2  show a face mask  100  which may be formed from the multi-layered splash resistant structure contemplated by the present invention. The face mask  100  includes a body portion  102  that is configured to be placed over the mouth and at least part of the nose of the user  108  such that the air exchanged through normal respiration passes through the body portion  102  of the face mask  100 . It is to be understood, however, that the body portion  102  can be of a variety of styles and geometries, such as, but not limited to, flat half mask, pleated face masks, cone masks, flat folded personal respiratory devices, duckbill style mask, trapezoidally shaped masks, etc. The body portion  102  may be configured to have one or more horizontal pleats, one or more vertical pleats, or no pleats, where such designs are generally known in the art. The face mask  100  therefore isolates the mouth and the nose of the user  108  from the environment. The face mask  100  is attached to the user  108  by a pair of tie straps  104  which are wrapped around the head of the user  108  (and a hair cap  106  if worn by the user) and are connected to one another. It is to be understood, however, that other types of fastening arrangements may be employed in accordance with various exemplary embodiments of the present invention. For instance, instead of the tie straps  104 , the face mask  100  may be attached to the user  108  by ear loops, elastic bands wrapping around the head, or a hook and loop type fastener arrangement, or the face mask  100  may be wrapped as a single piece around the head of the user  108  by an elastic band. The face mask  100  may also be directly attached to the hair cap  106 . 
     Additionally, the configuration of the face mask  100  may be different in accordance with various exemplary embodiments. In this regard, the face mask  100  may be made such that it covers both the eyes, hair, nose, throat, and mouth of the user. As such, the present invention is not limited to only face masks  100  that cover only the nose and mouth of the user  108 . 
     Meanwhile,  FIG. 3  shows a front view of a surgical gown  200  that can be formed from the splash resistant multi-layered structure contemplated by the present invention. The gown  200  can include a collar  202 , cuffs  204 , and shoulder seams  206  that link the sleeves  208  to the main body  210 . Other exemplary articles that can be formed from the splash resistant multi-layered structure of the present invention include surgical drapes or any other PPE in which splash resistant characteristics are desired. Further, the multiple layers of material in the multi-layered structure used to form the aforementioned face masks, surgical gowns, drapes, bouffant caps, etc. contemplated by the present invention may be joined by various methods, including adhesive bonding, thermal point bonding, or ultrasonic bonding. 
     The various components of the multi-layered splash resistant structure of the present invention are discussed in more detail below. 
     I. Plurality of Three-Dimensional Spacers 
     The multi-layered splash resistant structure of the present invention includes a plurality of three-dimensional spacers that are disposed on one or more outer-facing surfaces (i.e., surfaces facing away from the skin of the user) or inner-facing surfaces (i.e., surfaces facing towards the skin of the user) of the multi-layered structure. The plurality of three-dimensional spacers can be formed from a composition that includes a binder, an ink, a polymer, or a combination thereof, or any other component that can form a three-dimensional spacer when applied to one of the layers of material used to form the multi-layered structure, where such layers of material are discussed in more detail below. Specific examples of binders that can be suitable for forming the three-dimensional spacers contemplated by the present invention include an elastic puff (expandable) printing ink, a non-elastic puff (expandable) printing ink, an acrylic binder, a polyurethane binders, a thermoplastic material (e.g., a low temperature polyolefin hot melt adhesive or glue; a printing ink, or any other suitable binder, ink, adhesive, etc. or a combination thereof. Such binders can be obtained from Lubrizol or H.B. Fuller. Further, the binders can be water soluble. Although not required, in one embodiment, such binders, inks, adhesives, etc. can be hydrophobic, where the hydrophobicity of the binder, ink, adhesive, etc. can the enhance splash resistance by preventing fluid from penetrating subsequent layers of the article. 
     In one particular embodiment, the plurality of three-dimensional spacers can be formed from a phase change material (PCM) encapsulated within a binder and that are disposed on a layer of nonwoven material to provide said material with the ability to produce cooling with contact with the skin or to the microclimate of a face mask or other article incorporating the material. When a PCM is in its solid phase, it will absorb heat as the external temperature rises. The temperature of the PCM will mirror the external temperature until the PCM&#39;s melting point is reached. When the external temperature reaches the melt point of the PCM, the PCM will begin to melt. During the phase change process, the PCM will absorb large amounts of heat with almost no change in temperature. During this time period, the PCM is providing a cooling effect. The amount of time the PCM will provide a cooling effect is determined by the PCM&#39;s enthalpy of melting, also called the latent heat of fusion. The enthalpy or heat of fusion varies depending on the PCM material itself. In the case of PCMs, the enthalpy is typically measured in Joules/m 2 , where the larger the number of Joules/m 2 , the longer the PCM will provide a cooling effect for the same amount of PCM. The PCMs can be present on any suitable layer or layers of the face mask of the present invention so that the latent heat of fusion of the mask can be greater than about 2600 Joules/m 2 , such as from about 2600 Joules/m 2  to about 20,000 Joules/m 2 , such as from about 2800 Joules/m 2  to about 18,000 Joules/m 2 , such as from about 3000 Joules/m 2  to about 16,000 Joules/m 2 . Additionally, based on the total surface area of the layer of the mask on which the phase change material layer is disposed and the particular arrangement of the phase change material layer on the layer of the face mask, the phase change material can be present in the mask to provide at least about 30 Joules of cooling, such as from about 40 Joules to about 900 Joules of cooling, such as from about 50 Joules to about 800 Joules of cooling, such as from about 75 Joules to about 700 Joules of cooling, such as from about 100 Joules to about 600 Joules of cooling. 
     In another embodiment, the three-dimensional spacers can be formed from heat-activatable expandable inks, such as AQUAPUFF™ inks obtainable from Polytex Environmental Inks (Bronx, N.Y.). Other commercially available inks are available from Eastern Color and Chemical Company (Greenville, S.C.), International Coatings Company (Cerritos, Calif.), Dongguan City Haiya Printing Material Company (China), Atlas Screen Supply Company (Schiller Park, Ill.), NEHOC Australia Pty, Limited (Australia), and INX International Ink Corporation (Schaumburg, Ill.). Such inks are expandable inks which react when exposed to heat to produce a reaction that causes the ink to expand or “puff” into a three-dimensional spacer. The inks may include additives, known in the art as blowing agents, and can include chemicals which undergo physical or chemical changes on heating to form a gaseous product. Such additives include EXPANCEL™ 461 DU Microsphere (supplied by Expancel), Unicell OH (supplied by OMYA), Genitron LE (supplied by Acrol), or other gas-encapsulated thermoplastic microspheres. The printing of such inks onto one or more layers of the multi-layered structure used to form the face masks or other articles contemplated by the present invention can occur at a number of steps in the process, such as in an off-line printing step, or on-line during the article assembly process. Further, the ink can be printed at one process step, and expanded by heat activation in a later, downstream step. 
     In some embodiments, the three-dimensional spacers can include an optional amount of moisture absorbing polymer. The polymer can be present in the three-dimensional spacers in an amount as desired. For example, in some aspects, the three-dimensional spacers can contain up to about 1 wt. %, such as up to about 5 wt. %, or even up to about 10 wt. % or more of a moisture absorbing polymer. Examples of suitable moisture absorbing polymers include, but are not limited to, polyethylene oxide, polyethylene glycol, polyvinyl alcohol, polyvinyl pyrrolidones, polyvinyl pyridine, or a combination thereof. 
     In some embodiments, the three-dimensional spacers can include an optional elastomeric polymer. The elastomeric polymer can make the foam structure resilient and can help with moisture absorbency by trapping water like a sponge. Further, the elastomeric polymer may add resilience or flexibility to the three-dimensional spacers. The elastomeric polymer component can be present in an amount which is effective to achieve the desired dimensional change properties. For example, the three-dimensional spacers can contain up to about 1 wt. %, such as up to about 5 wt. %, or even up to about 10 wt. % or more of an elastomeric polymer to provide improved properties. Examples of suitable elastomeric polymers include, but are not limited to, thermoplastic polyurethanes, olefinic elastomeric polymers)(Vistamaxx®, poly(ether-amide) block copolymers, thermoplastic rubbers such as uncrosslinked polyolefins, styrene-butadiene copolymers, silicon rubbers, synthetic rubbers such as nitrile rubber, styrene isoprene copolymers, styrene ethylene butylenes copolymers, butyl rubber, nylon copolymers, spandex fibers comprising segmented polyurethane, ethylene-vinyl acetate copolymer or a combination thereof. 
     Additionally, adhesion promoters can be added to the three-dimensional spacers. For example, Carboset 514H, available commercially from Noveon, Inc. of Cleveland, Ohio, is an acrylic colloidal dispersion polymer supplied in ammonia water, which can dry to a clear, water-resistant, non-tacky thermoplastic film. Such adhesion promotes facilitate the attachment of the three-dimensional spacers to the layer of material on which they are applied. 
     In addition, the three-dimensional spacers can contain a coloring agent (e.g., pigment or dye), a solvent, and any other desired ingredients. Typically, a pigment refers to a colorant based on inorganic or organic particles which do not dissolve in water or solvents. Usually pigments form an emulsion or a suspension in water. On the other hand, a dye generally refers to a colorant that is soluble in water or solvents. The pigment or dye can be present in the three-dimensional spacers in an amount ranging from about 0.25 wt. % to about 40 wt. %, such as from about 0.5 wt. % to about 30 wt. %, such as from about 1 wt. % to about 20 wt. % on a dry weight basis after the spacers have formed to the layer of material on which they have been applied. 
     Suitable organic pigments include dairylide yellow AAOT (for example, Pigment Yellow 14 CI No. 21 095), dairylide yellow AAOA (for example, Pigment Yellow 12 CI No. 21090), Hansa Yellow, CI Pigment Yellow 74, Phthalocyanine Blue (for example, Pigment Blue 15), lithol red (for example, Pigment Red 52:1 CI No. 15860:1), toluidine red (for example, Pigment Red 22 CI No. 12315), dioxazine violet (for example, Pigment Violet 23 CI No. 51319), phthalocyanine green (for example, Pigment Green 7 CI No. 74260), phthalocyanine blue (for example, Pigment Blue 15 CI No. 74160), naphthoic acid red (for example, Pigment Red 48:2 CI No. 15865:2). Suitable inorganic pigments include titanium dioxide (for example, Pigment White 6 CI No. 77891), carbon black (for example, Pigment Black 7 CI No. 77266), iron oxides (for example, red, yellow, and brown), ferric oxide black (for example, Pigment Black 11 CI No. 77499), chromium oxide (for example, green), ferric ammonium ferrocyanide (for example, blue), and the like. 
     Suitable dyes that may be used include, for instance, acid dyes, and sulfonated dyes including direct dyes. Other suitable dyes include azo dyes (e.g., Solvent Yellow 14, Dispersed Yellow 23, and Metanil Yellow), anthraquinone dyes (e.g., Solvent Red 111, Dispersed Violet 1, Solvent Blue 56, and Solvent Orange 3), xanthene dyes (e.g., Solvent Green 4, Acid Red 52, Basic Red 1, and Solvent Orange 63), azine dyes (e.g., Jet Black), and the like. 
     The three-dimensional spacers can be applied to an outer-facing surface or an inner-facing surface of any layer of material present in the splash resistant articles of the present invention. To apply the spacers, the ink, binder, or polymer composition is generally dispersed or dissolved in water or another low viscosity carrier. In addition to using water as a solvent, exemplary solvents that can be used may include aliphatic hydrocarbons with common binder types, such as polyamide, shellac, nitro-cellulose, and styrene-maleic. Generally, solvent-based treatments include non-catalytic, block urethane resin, which generally demonstrate superior durability over traditional flexographic binders, such as styrene-maleic, rosin-maleic, and acrylic solutions. Desired solvent blends include various acetates such as ethyl acetate, N-propyl acetate, isopropyl acetate, isobutyl acetate, N-butyl acetate, and blends thereof; various alcohols including ethyl alcohol, isopropyl alcohol, normal propyl alcohol, and blends thereof; and glycol ethers including EKTASOLVE™, EP (ethylene glycol monopropyl ether), EB (ethylene glycol monobutyl ether), DM (diethylene glycol monomethyl ether), DP (diethylene glycol monopropyl ether), and PM (propylene glycol monomethyl ether), which may be obtained from Eastman Chemical of Kingsport, Tenn. Other glycols that may also be used are DOWANOL™ obtainable from Dow Chemical of Midland, Mich. A desired solvent blend may be a blend of about 50% to about 75% glycol ether, about 25% to about 35% N-propyl acetate, and about 15% to about 25% N-butyl acetate. 
     Suitable water-based three-dimensional spacers that may be used may further include emulsions that may be stabilized in water-ammonia and may further comprise alcohols, glycols, or glycol ethers as co-solvents. Generally, organic solvents (less than or equal to about 7 wt. %) may be added to water-based treatments: alcohols, for example, propan-2-ol may be added for speeding up drying and assisting wetting, glycols, for example, mono propylene glycol to slow down drying, glycol ethers, for example, dipropyl glycol mono methyl ether to aid film formation. Such solvents may be commodity chemicals, commercially available from various companies. Generally, water-based treatments include self-crosslinking acrylic copolymer emulsion, which may have demonstrated superior durability over traditional non-crosslinking binders such as acrylic solutions and dispersion copolymers. Besides the solvent and pigments, the heat-activatable expandable treatment may comprise a binder. The binder helps stabilize the composition used to form the three-dimensional spacers onto the layer of material to which it is being applied. 
     In addition to the phase change materials discussed above, other encapsulated functional additives can be combined within one of the binders, adhesives, or inks discussed above and then applied to one or more layers of the multi-layered structure of the present invention to provide an added benefit to the user of an article formed from the multi-layered structure. The functional additive can be released from its encapsulant upon crushing of the microencapsulated functional additive, which could occur when the article of the present invention is opened from its packaging, unfolded, etc. or when the article of the present invention is wetted with a fluid. For instance, the plurality of three-dimensional spacers can include an antimicrobial agent to provide antimicrobial protection, a fragrance for odor control, a topical ointment for skincare, a therapeutic agent to provide a specific treatment, an absorbent material such as activated carbon for moisture or odor control, a superabsorbent material, or any other additive that could be useful in an article used as PPE. For instance, a fragrance can be encapsulated into microcapsules that are then incorporated into a binder to form the three-dimensional spacers of the present invention, and when an article containing the three-dimensional spacers is wetted, the fragrance could be released due to “crushing” or “disintegration” of the microcapsules containing the fragrance in order to mask an odor or release a scent, perhaps as an indicator of the article or layer of material being splashed. In another embodiment, a superabsorbent material can be incorporated into a binder to form the three-dimensional spacers of the present invention, and when an article containing the three-dimensional spacers is wetted, the superabsorbent material could be activated in order to help contain the a fluid insult. It should be understood that although “crushing” or “disintegration” of the microcapsules containing the antimicrobial, fragrance, topical ointment, or therapeutic agent, may be required to activate such additives, “crushing” or “disintegration” of the microcapsules containing the phase change material functional additive, the absorbent material, or the superabsorbent material discussed above is not required. 
     Regardless of the particular encapsulated functional additives utilized, the functional additives can be encapsulated in such a way to provide functional permanency over longer time or to provide time-release of the functionalities mentioned above over different frequencies of time. Such additives can be present in the three-dimensional spacers in an amount ranging from about 0.25 wt. % to about 70 wt. %, such as from about 0.5 wt. % to about 60 wt. %, such as from about 1 wt. % to about 50 wt. % on a dry weight basis after the spacers have formed to the layer of material on which they have been applied. 
     Moreover, the specific composition of the plurality of three-dimensional spacers, the three-dimensional spacers can be applied to one or more layers of material of the multi-layered structure of the present invention in any suitable pattern or in a random fashion. If the three-dimensional spacers are applied in a pattern, the pattern can be continuous or discontinuous. In one particular embodiment as shown in  FIG. 4 , the three-dimensional spacers  302  can be applied to a layer of the multi-layered structure  300  in the form of a series dots having a semi-circular shape and a maximum height S, where the dots are arranged in a series of offset columns  304  and a series of offset rows  306  to form channels  314  therebetween. In other embodiments, the three-dimensional spacers can be in the form of lines, crosses, gridlines, logos, or any other form or shape and can have any density, height, or texture so long as the three-dimensional spacers provide for sufficient spacing between the layers of material used to form the multi-layered structure of the present invention so that the splash resistant properties of the multi-layered structure can be achieved. In any event, the particular dimensions, shape, and spacing of the three-dimensional spacers is a function of the materials being used. As the intent is to provide a gap between the layers of materials used to form an article in order to dissipate the energy of the impact of the splash, the stiffer the layers are, especially the outer layer, the smaller, shorter, and more disperse the three-dimensional spacers (e.g., dots) can be. Meanwhile, as the drapability or flexibility of the outer layer of material increases, the three-dimensional spacers (e.g., dots) may need to be taller and/or closer together in order to minimize the potential contact between the adjacent layers of material, where such contact is what leads to fluid transfer through the subsequent layer. 
     Once applied to a layer of material, the three-dimensional spacers can have various textures. For instance, as discussed above, the three-dimensional spacers can be “puffy” or malleable (e.g., soft and cushiony), which can impart improved pressure distribution capabilities to the multi-layered structure incorporating the three-dimensional spacers, such as when the multi-layered structure is used in a face mask, or the three-dimensional spacers can have a rigid texture to provide the multi-layered structure with structural stability and prevent compression of the multi-layered structure when a fluid insult occurs. It should also be understood that the three-dimensional spacers can be present on from about 5% to about 100%, such as from about 10% to about 99.5%, such as from about 15% to about 99% of the surface area of the layer of material on which the three-dimensional spacers are applied. Further, the three-dimensional spacers can be applied to a layer of material in a composition that also includes a binder or carrier using any known method such as a gravure roll, slot coating, continuous spraying, discontinuous spraying, screen printing, ink jet printing, etc. In addition, heat can be applied after a composition containing the three-dimensional spacers has been applied to a layer of material to activate the plurality of three-dimensional characteristics of the spacers present on the layer of material, such as when the three-dimensional spacers are in the form of a “puffable” ink. 
     Regardless of the particular type of material used to form the three-dimensional spacers, the three-dimensional spacers can be in the form of dots, grids, logos, crosses, etc. which can have a width, length, or diameter of from about 0.25 mm to about 5 mm and can have a height S ranging from about 0.025 mm to about 3 mm. Further, the three-dimensional spacers can be hard, soft, or foam-like as needed by the application. In addition, the three-dimensional spacers (e.g., dots, crosses, logos, etc.) can be applied to the various layers of the multi-layered structure in an amount ranging from about 1% to about 70% of the total surface area of the surface to which the spacers are applied for breathable barrier or porous materials and in an amount ranging from about 1% to about 100% of the total surface area of the surface to which the spacers are applied for non-porous/non-breathable materials. 
     II. Layers of Material 
     The plurality of three-dimensional spacers discussed above can be applied to one or more layers of material in the multi-layered structure contemplated by the present invention. For example, the layers of the multi-layered structure can be formed from one or more non-woven materials (e.g., a spunbond, meltblown, SMS laminate, spunlace, hydroentangled, carded, elastomeric, or foam webs), one or more films, or any combination thereof, and the three-dimensional spacers can be present on any one of the aforementioned layers of material, where the spacers can be present on the layer of material&#39;s outer-facing surface, inner-facing surface, or both. The splash resistance, as measured by ASTM F1862-13, can be further enhanced if the materials in the multi-layered structure are hydrophobic, either naturally or through additives or treatments. This can reduce the potential for wicking of the fluid insult through the layers. Further, the three-dimensional spacers can be present on more than one of the layers of material in the multi-layered structure of the present invention. Moreover, the various layers of material used to form the multi-layered structure can each have basis weights ranging from about 10 gsm to about 150 gsm, such as from about 12.5 gsm to about 100 gsm, such as from about 15 gsm to about 80 gsm. For example, any meltblown material layers can have a basis weight ranging from about 10 gsm to about 75 gsm, such as from about 12.5 gsm to about 70 gsm, such as from about 15 gsm to about 50 gsm. Further, any spunlace or bicomponent nonwoven material layers can have a basis weight ranging from about 10 gsm to about 25 gsm, such as from about 12.5 gsm to about 20 gsm, such as from about 15 gsm to about 17.5 gsm. In addition, any spunbond material layers can have a basis weight ranging from about 15 gsm to about 60 gsm, such as from about 20 gsm to about 50 gsm, such as from about 20 gsm to about 45 gsm. In addition, the basis weight of the three-dimensional spacer layer, which includes the encapsulated PCM and binder (in various ratios of encapsulated PCM and binder holding it in place) disposed on a nonwoven material can range from about 20 gsm to about 300 gsm, such as from about 30 gsm to about 250 gsm, such as from about 40 gsm to about 200 gsm, such as from about 50 gsm to about 150 gsm, such as from about 60 gsm to about 140 gsm. In one particular embodiment, the basis weight of the three-dimensional spacer layer, which includes the encapsulated PCM and binder (in various ratios of encapsulated PCM and binder holding it in place) disposed on a nonwoven material can range from about 90 gsm to about 110 gsm. 
     A spunbond web is one type of nonwoven material that can be used in one or more layers of the multi-layered structure of the present invention. A spunbond web is a material made from small diameter fibers which are formed by extruding molten thermoplastic material as filaments from a plurality of fine, usually circular capillaries of a spinneret with the diameter of the extruded filaments then being rapidly reduced as by, for example, in U.S. Pat. Nos. 4,340,563; 3,692,618; 3,802,817; 3,338,992; 3,341,394; 3,502,763; and 3,542,615. Spunbond fibers are generally not tacky when they are deposited onto a collecting surface. Spunbond fibers are generally continuous and have average diameters (from a sample of at least 10) larger than 7 microns, more particularly, between about 10 and 20 microns. 
     A meltblown web can also be used in one or more layers of the multi-layered structure of the present invention. A meltblown web is formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten threads or filaments into converging high velocity, usually hot, gas (e.g. air) streams which attenuate the filaments of molten thermoplastic material to reduce their diameter, which may be to microfiber diameter. The meltblown fibers are then carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly dispersed meltblown fibers. Such a process is disclosed, for example, in U.S. Pat. No. 3,849,241. Meltblown fibers are microfibers which may be continuous or discontinuous, are generally smaller than 10 microns in average diameter, and are generally tacky when deposited onto a collecting surface. 
     A laminate of spunbond and meltblown materials, (e.g., a spunbond/meltblown/spunbond (SMS) laminate) can also be used in one or more layers of the multi-layered structure of the present invention. Such a laminate and others are described in U.S. Pat. Nos. 4,041,203; 5,169,706; 5,145,727; 5,178,931; and 5,188,885. Such a laminate may be made by sequentially depositing onto a moving forming belt first a spunbond layer, then a meltblown layer and last another spunbond layer and then bonding the laminate in a manner described below. Alternatively, the layers may be made individually, collected in rolls, and combined in a separate bonding step. Such laminates usually have a basis weight of from about 0.1 to 12 osy (6 to 400 gsm), or more particularly from about 0.75 to about 3 osy. Multilayer laminates may also have various numbers of meltblown (abbreviated as “M”) layers or multiple spunbond (abbreviated as “S”) layers in many different configurations and may include other materials like films (abbreviated as “F”) or coform materials (see U.S. Pat. No. 4,100,324 for descriptions of exemplary coform materials). Examples include SMMS laminates, SM laminates, SFS laminates, etc. 
     A hydroentangled web can also be used in one or more layers of the multi-layered structure of the present invention. Hydroentangled webs can also be used in one or more layers of the multi-layered structure of the present invention. A hydroentangled web is a web formed by a process wherein a nonwoven web, or layers of a non-woven web, are subjected to streams of a non-compressible fluid, e.g., water, at a high enough energy level and for a sufficient time to entangle the fibers thereof. The fluid may advantageously be used at a pressure of between about 200 and 5000 psig (14-351 kg/cm 2  gauge) from a distance of a few inches (centimeters) above the web while the web is supported by a mesh structure. This process is described in detail in U.S. Pat. No. 3,486,168. Nonwoven webs subjected to hydroentangling are referred to as, for example, spunlace materials. 
     A bonded carded web can also be used in one or more layers of the multi-layered structure of the present invention. A bonded carded web is a nonwoven web that is made from staple fibers which are sent through a combing or carding unit, which separates or breaks apart and aligns the staple fibers in the machine direction to form a generally machine direction-oriented fibrous nonwoven web. This material may be bonded together by methods that include point bonding, through air bonding, ultrasonic bonding, adhesive bonding, etc. 
     An airlaid web can also be used in one or more layers of the multi-layered structure of the present invention. An airlaid web is a nonwoven web formed by a process in which a fibrous nonwoven layer can be formed. In the airlaying process, bundles of small fibers having typical lengths ranging from about 3 to about 52 millimeters (mm) are separated and entrained in an air supply and then deposited onto a forming screen, usually with the assistance of a vacuum supply. The randomly deposited fibers then are bonded to one another using, for example, hot air or a spray adhesive. Airlaying is taught in, for example, U.S. Pat. No. 4,640,810. 
     Various layers made from elastomeric webs and foam webs are also contemplated for use in the multi-layered structure of the present invention. 
     The multi-layered structures of the present invention can also include one more layers of thin, breathable films that are commonly made from thermoplastic polyolefins like polyethylene and polypropylene and copolymers thereof because of their relatively low cost and ability to be processed. Polyethylene is generally used in the film production and when used in articles such as gowns or drapes, the film can be commonly “filled” with calcium carbonate, various kinds of clay, silica, alumina, barium carbonate, sodium carbonate, magnesium carbonate, talc, barium sulfate, magnesium sulfate, aluminum sulfate, titanium dioxide, zeolites, cellulose-type powders, kaolin, mica, carbon, calcium oxide, magnesium oxide, aluminum hydroxide, pulp powder, wood powder, cellulose derivatives, chitin and chitin derivatives, to increase breathability, while when used in articles such as masks, the film should be perforated or apertured to allow for the passage of air. Fillers produce microscopic pores in the film upon stretching to increase porosity. Unfortunately, these thin and breathable films are considered to be thermally sensitive because they have a tendency to become compromised by heat and/or or pressure. When these films are incorporated into laminate barrier materials by sandwiching them together with various combinations of other materials such as, for example, spunbond layers, meltblown layers and combinations thereof, the resulting laminate barrier materials are generally considered to be thermally sensitive as well. This characterization is particularly important for post-laminate formation processing steps. That is, manufacturing operations that convert the thermally sensitive barrier materials after such films are formed into the laminate barrier materials. For example, when thermally sensitive barrier materials are converted into gowns or other articles utilizing thermal point bonding and/or ultrasonic bonding techniques or when components such as, for example, tie cords or other features are attached to the articles, the breathable films of barrier laminate are frequently compromised such that they so longer provide desired levels of barrier to liquid penetration and pathogens. In one particular embodiment, the present invention provides for a multi-layered structure which incorporates a layer of material having a pattern or random distribution of three-dimensional spacers applied thereon. Such a layer improves the ability of the multi-layered structure to resist penetration by a splash of fluid by reducing the contact of adjacent layers of material and/or absorbing the energy produced by a fluid impact on the multi-layered structure, and/or providing for a mechanism by which fluid that strikes the multi-layered structure may be channeled away from the point of contact. 
     In another embodiment, one or more of the layers of the multi-layered structure, such as the inner layer, can be formed from a high opacity hydrophobic material. The use of such a material can further enhance the ability of the multi-layered structure to prevent fluids from passing through the inner layer and can help avoid the potential false positives (failures) in the ASTM F1862-13 test, which can happen with thin or translucent materials are used for the inner layer of the multi-layered structure. When such thin or translucent materials are used and the blood breaches the layer of material that is adjacent the inner layer, it can appear that all layers of the multi-layered structure have been breached resulting in a failure per the ASTM F1862-13 method, even when a breach of the inner layer has not actually occurred. 
     Regardless of the particular materials used to form the two or more layers of the multi-layered structure contemplated by the present invention, the multi-layered structure can be formed into various articles of personal protective equipment including, but not limited to, face masks, surgical gowns, surgical drapes, bouffant caps, and the like as discussed above. 
     III. Arrangement of the Three-Dimensional Spacers and Layer of Material 
     The three-dimensional spacers and layers of material discussed above can be arranged in various embodiments to form a multi-layered structure that improves splash resistance and can be employed in face masks, surgical gowns, surgical drapes, bouffant caps, and other PPE, where the forced separation of layers facilitated by the plurality of three-dimensional spacers enhances the splash resistance of the multi-layered structure without the adding bulk, weight, and discomfort that occur when splash resistance is increased via the use of additional layers of material. Turning now to  FIGS. 5 and 6 , two layers of a multi-layered structure of the present invention are shown to demonstrate the functionality of the three-dimensional spacers when a fluid insult such is introduced to the multi-layered structure. 
     Specifically,  FIG. 5  is a cross-sectional view of a multi-layered structure that includes an inner layer of material  300  and an outer layer of material  400  prior to an insult of a bodily fluid  308 , such as blood, where the inner layer of material  300  is the layer closest to the skin of a user and the outer layer of material  400  is the layer furthest from the user when the structure is part of PPE such as a face mask, surgical gown, surgical drape, bouffant cap, etc. The inner layer of material  300  includes an outer-facing surface  310  and an inner-facing surface  312 , while the outer layer of material  400  includes an outer-facing surface  402  and an inner-facing surface  404 . A plurality of three-dimensional spacers  302  are disposed on the outer-facing surface  310  of the inner layer of material  300 , and the three-dimensional spacers  302  have a maximum height S. The distance D between the outer-facing surface  310  of the inner layer of material  300  and the inner-facing surface  404  of the outer layer of material  400  is at least as large as the maximum height S, where the maximum height S of the three-dimensional spacers  302  forces separation between the inner layer of material  300  and the outer layer of material  400 . Such an arrangement enhances the fluid barrier and splash resistance of the multi-layered structure of the present invention. In particular, the separation between the layers helps to reduce the area of contact between the layers and thus lowers the ability of fluid to transfer from one layer to the next. As such, the three-dimensional spacers  302  therefore help to separate the layers of material  300  and  400  such that fluid cannot be as easily transferred through the layers by decreasing the area of surface contact between the layers. 
     Further, the three-dimensional spacers  302  define channels  314  that are located adjacent the a surface of a layer of material on which the three-dimensional spacers  302  are disposed, which happens to be the outer-facing surface  310  of the inner layer  300  in the particular multi-layered structure of  FIG. 5 , although it is to be understood that the three-dimensional spacers  302  and channels  314  can be present on an inner or outer-facing surface of any layer. By providing the channels  314 , a fluid insult may be transferred and more uniformly distributed across a layer when the layer is contacted with the fluid insult. This separation also provides for a contained space in which the fluid can easily flow laterally when the layers are compressed, which also helps prevent the fluid from transferring through the layers. This distribution of fluid helps to prevent the accumulation of a pool of fluid at a particular location on the outer surface of a layer. It is typically the case that fluid which is heavily concentrated at a particular location on a layer of the multi-layered structure is more likely to be transferred through that layer of the multi-layered structure, as opposed to the situation in which the same amount of fluid were distributed over a larger portion of the outer surface of the layer. The channels  314  may be interconnected channels such that all of the channels  314  are in communication with one another. This allows for the advantage of having fluid which contacts a layer at any point of contact  318  to be distributed through a larger number of channels  314 . Alternatively, the channels  314  may be configured such that only a portion of the channels  314  are in communication with one another. Further, the channels  314  may be provided in any number in accordance with other exemplary embodiments of the present invention. The channels  314  may thus redirect fluid which contacts a layer to a desired location. For instance, the channels  314  may be configured such that fluid which engages a layer of material at the point of contact  318  is redirected along the outer surface that layer and flows through the multi-layered structure to a position along, for instance, the edge of the multi-layered structure. 
       FIG. 6  shows the functionality of the three-dimensional spacers  302  and channels  314  during an insult of a bodily fluid  308 . As shown, the three-dimensional spacers  302  are configured such that their three-dimensional structure enables the outer layer of material  400  to flex and absorb at least a portion of the forces transmitted by the fluid  308  striking the outer-facing surface  402  of the outer layer of material  400  without allowing the inner-facing surface  404  to contact the outer facing surface  310  of the inner layer material  300 . In this regard, the presence of the three-dimensional spacers  302  having a maximum height S results in the space between the inner-facing surface  404  of the outer layer of material  400  and the outer-facing surface  310  of the inner layer of material  300  having a distance D that is at least as large as the maximum height S. Absorption of the aforementioned forces imparted by a fluid strike may help to prevent fluid from penetrating past the inner layer of material  300  of the multi-layered structure of the present invention. In this regard, it may be the case that fluid is already trapped between one or more layers of the multi-layered structure of the present invention. Forces imparted by the fluid  308  striking the multi-layered structure cause these already trapped fluids to be pushed further through the structure. However, due to the formation of a plurality of channels  314  as a result of the forced separation between the layers  300  and  400  created by the presence of the three-dimensional spacers  302 , these trapped fluids can be prevented from propagating through the inner most layers of the multi-layered structure and contacting the skin or the user of PPE formed from the multi-layered structure of the present invention. 
     As stated, the various multi-layered structures contemplated by the present invention and shown in  FIGS. 8-12  may be composed of two or more of layers  802 ,  804 ,  806 , and  808 . The arrangement of the layers  802 ,  804 ,  806 , and  808  may be modified such that any combination of sequencing is possible and such that anywhere from two to four layers can be utilized, where the four-layered structures  800 ,  860 , and  870 , and the three-layered structures  880  and  890  represent some of the particular embodiments contemplated by the present invention. Further, it should be understood that the outer layer  802 , middle layers  804  and  806 , and the inner layer  808  may be made of the same materials or different materials. In addition, a plurality of three-dimensional spacers can be applied to the inner-facing surface, the outer-facing surface, or both of any of the layers of material  802 ,  804 ,  806 , and  808 . Moreover, additional layers other than those shown in the figures may also be incorporated into the multi-layered structure to achieve the desired properties, although the present inventors have found that sufficient splash resistance can be achieved with the use of fewer layers than taught in the art, which is due, at least in part, to the incorporation of the three-dimensional spacers  302  into the various multi-layered structures  800 ,  860 ,  870 ,  880 , and  890 . The additional layers may be constructed from various materials known to those skilled in the art such as those described above. Specific embodiments of the multi-layered structure construction are discussed in more detail below, although it is to be understood that the present invention contemplates any other suitable arrangement of multiple layers of material where a plurality of three-dimensional spacers are applied to one or both surfaces of any of the multiple layers of material. 
     Turning now to  FIG. 8 , a four-layered structure  800  is illustrated according to one embodiment of the present invention. The multi-layered structure  800  has four layers including an outer layer of material  802  and an inner layer of material  808 , where the outer layer of material  802  includes an outer-facing surface  810  and an inner-facing surface  818 , and the inner layer of material  808  includes an outer-facing surface  824  and an inner-facing surface  812 . Disposed between the outer layer of material  802  and the inner layer of material  808  are a layer of material  804  and a layer of material  806 . The layer of material  804  is positioned adjacent the outer layer of material  802  and includes an outer-facing surface  814  and an inner-facing surface  816 . Meanwhile, the layer of material  806  is positioned adjacent the inner layer of material  808  and includes an outer-facing surface  820  and an inner-facing surface  822 . As shown in  FIG. 8 , a plurality of three-dimensional spacers  302  are disposed on the outer-facing surface  814  of the layer of material  804 , which, in this particular embodiment, can also be referred to as the second layer of material present past the outer-facing surface  810  of the outer layer of material  802 , which also serves as the outer-facing surface of the entire multi-layered structure. The plurality of three-dimensional spacers  302  define a plurality of channels  314  that are formed between the outer layer of material  802  and the layer of material  804 . Further, the plurality of three-dimensional spacers  302  create a forced separation or space between the outer-facing surface  814  of the second layer of material  804  and the inner-facing surface  818  of the first (or outermost) layer of material  802 . The separation between the outer-facing surface  814  of the second layer of material  804  and the inner-facing surface  818  of the first layer of material  802  spans a distance D, which is controlled at least in part by the maximum height S of the three-dimensional spacers  302 . In the specific embodiment of  FIG. 8 , the outer (first) layer of material  802 , the second layer of material  804  on which the three-dimensional spacers  302  are disposed, and the inner (fourth) layer of material  808  are spunbond webs, while the third layer of material  806  positioned adjacent the inner layer of material  808  is a meltblown web. Further, in the specific embodiment of  FIG. 8 , the three-dimensional spacers  302  are formed from a binder which contains an encapsulated phase change material. 
     The multi-layered structure  800  was tested for splash resistance according to ASTM Standard F-1862 (Level 3), where the fluid was prevented from passing through the three-dimensional spacers  302  present on the outer-facing surface  814  of the spunbond layer of material  804 , which is the second layer past the point of fluid contact at the outer-facing surface  810  of the outer layer of material  802 . In other words, the multi-layered structure  800  of  FIG. 8  required only two layers of material (e.g., spunbond layer  802  and spunbond layer  804  having the three-dimensional spacers  302  present on its outer-facing surface  814 ) to prevent passage of fluid through the multi-layered structure. 
     Next,  FIG. 9  shows another four-layered structure  860  according to another embodiment of the present invention. The multi-layered structure  860  has four layers including an outer layer of material  802  and an inner layer of material  808 , where the outer layer of material  802  includes an outer-facing surface  810  and an inner-facing surface  818 , and the inner layer of material  808  includes an outer-facing surface  824  and an inner-facing surface  812 . Disposed between the outer layer of material  802  and the inner layer of material  808  are a layer of material  806  and a layer of material  804 . The layer of material  806  is positioned adjacent the outer layer of material  802  and includes an outer-facing surface  820  and an inner-facing surface  822 . Meanwhile, the layer of material  804  is positioned adjacent the inner layer of material  808  and includes an outer-facing surface  814  and an inner-facing surface  816 . As shown in  FIG. 9 , a plurality of three-dimensional spacers  302  are disposed on the outer-facing surface  814  of the layer of material  804 , which, in this particular embodiment, can also be referred to as the third layer of material present past the outer-facing surface  810  of the outer layer of material  802 , which also serves as the outer-facing surface of the entire multi-layered structure. The plurality of three-dimensional spacers  302  define a plurality of channels  314  that are formed between the layer of material  806  and the layer of material  804 . Further, the plurality of three-dimensional spacers  302  create a forced separation or space between the outer-facing surface  814  of the third layer of material  804  and the inner-facing surface  822  of the second layer of material  806 . The separation between the outer-facing surface  814  of the third layer of material  804  and the inner-facing surface  822  of the second layer of material  806  spans a distance D, which is controlled at least in part by the maximum height S of the three-dimensional spacers  302 . In the specific embodiment of  FIG. 9 , the outer (first) layer of material  802 , the third layer of material  804  on which the three-dimensional spacers  302  are disposed, and the inner (fourth) layer of material  808  are spunbond webs, while the second layer of material  806  positioned adjacent the outer layer of material  802  is a meltblown web. Further, in the specific embodiment of  FIG. 9 , the three-dimensional spacers  302  are formed from a binder which contains an encapsulated phase change material. 
     The multi-layered structure  860  was tested for splash resistance according to ASTM Standard F-1862 (Level 3), where the fluid did pass through the three-dimensional spacers  302  present on the outer-facing surface  814  of the spunbond layer of material  804 , which in the specific multi-layered structure  860  is the third layer past the point of fluid contact at the outer-facing surface  810  of the outer layer of material  802 . However, the fluid did not pass through the entire multi-layered structure. In other words, the multi-layered structure  860  of  FIG. 9  required three layers of material (e.g., spunbond layer  802 , meltblown layer  806 , and spunbond layer  804  having the three-dimensional spacers  302  present on its outer-facing surface  814 ) to prevent passage of fluid through the multi-layered structure. Comparing the multi-layered structure  800  of  FIG. 8  to the multi-layered structure  860  of  FIG. 9 , it appears that the three-dimensional spacers  302  provide better splash resistance when positioned immediately adjacent a spunbond layer or any layer other than a meltblown layer that catches a majority of the initial fluid insult. The present inventors hypothesize that this may be the case because the three-dimensional spacers are configured in such an arrangement have more room between the layers and can repel the initial pressure of the fluid insult, after which the layers exposed to the fluid insult are positioned closer to each other, resulting the fluid absorbing through the layers. 
     In addition,  FIG. 10  illustrates a four-layered structure  870  according to one more embodiment of the present invention. The multi-layered structure  870  has four layers including an outer layer of material  802  and an inner layer of material  808 , where the outer layer of material  802  includes an outer-facing surface  810  and an inner-facing surface  818 , and the inner layer of material  808  includes an outer-facing surface  824  and an inner-facing surface  812 . Disposed between the outer layer of material  802  and the inner layer of material  808  are a layer of material  804  and a layer of material  806 . The layer of material  804  is positioned adjacent the outer layer of material  802  and includes an outer-facing surface  814  and an inner-facing surface  816 . Meanwhile, the layer of material  806  is positioned adjacent the inner layer of material  808  and includes an outer-facing surface  820  and an inner-facing surface  822 . 
     As shown in  FIG. 10 , a plurality of three-dimensional spacers  302  are disposed on the outer-facing surface  814  of the layer of material  804 , which, in this particular embodiment, can also be referred to as the second layer of material present past the outer-facing surface  810  of the outer layer of material  802 , which also serves as the outer-facing surface of the entire multi-layered structure. The plurality of three-dimensional spacers  302  define a plurality of channels  314  that are formed between the outer layer of material  802  and the layer of material  804 . Further, the plurality of three-dimensional spacers  302  create a forced separation or space between the outer-facing surface  814  of the second layer of material  804  and the inner-facing surface  818  of the first (or outermost) layer of material  802 . The separation between the outer-facing surface  814  of the second layer of material  804  and the inner-facing surface  818  of the first layer of material  802  spans a distance D, which is controlled at least in part by the maximum height S of the three-dimensional spacers  302 . In addition, a plurality of three-dimensional spacers  302  are also disposed on the inner-facing surface  812  of the inner layer of material  808 , where the three-dimensional spacers  302  also define a plurality of channels  314 . Further, the plurality of three-dimensional spacers  302  present on the inner-facing surface  812  of the inner layer of material  808  can create a forced separation between a user&#39;s skin and the inner layer of material  808  to provide for added comfort to the user since the multi-layered structure  870  only contacts the user at the three-dimensional spacers  302  rather than across the entire inner-facing surface  812  as in multi-layered structures  800  and  860 . The separation is controlled at least in part by the maximum height S of the three-dimensional spacers  302 . 
     In the specific embodiment of  FIG. 10 , the outer (first) layer of material  802 , the second layer of material  804  on which a plurality of three-dimensional spacers  302  are disposed, and the inner (fourth) layer of material  808  are spunbond webs, while the third layer of material  806  positioned adjacent the inner layer of material  808  is a meltblown web. Further, in the specific embodiment of  FIG. 10 , the three-dimensional spacers  302  present on the outer-facing surface  814  of the second layer of material  804  are in the form of an acrylic binder, while the three-dimensional spacers  302  present on the inner-facing surface  812  of the inner layer  808  are formed from a binder which contains an encapsulated phase change material so that the three-dimensional spacers  302  present on the inner-facing surface  812  not only minimize the degree of contact between the multi-layered structure  870  and the user, but can also facilitate additional cooling to the user. 
     The multi-layered structure  870  was tested for splash resistance according to ASTM Standard F-1862 (Level 3), where the fluid was prevented from passing through the three-dimensional spacers  302  present on the outer-facing surface  814  of the spunbond layer of material  804 , which is the second layer past the point of fluid contact at the outer-facing surface  810  of the outer layer of material  802 . In other words, the multi-layered structure  870  of  FIG. 10  required only two layers of material (e.g., spunbond layer  802  and spunbond layer  804  having the three-dimensional spacers  302  present on its outer-facing surface  814 ) to prevent passage of fluid through the multi-layered structure. 
     Meanwhile,  FIG. 11  shows a three-layered structure  880  according to an additional embodiment of the present invention in which the spunbond layer  804  has been eliminated. The multi-layered structure  880  has three layers including an outer (first) layer of material  802  and an inner (third) layer of material  808 , where the outer (first) layer of material  802  includes an outer-facing surface  810  and an inner-facing surface  818 , and the inner (third) layer of material  808  includes an outer-facing surface  824  and an inner-facing surface  812 . Disposed between the outer (first) layer of material  802  and the inner (third) layer of material  808  is a second layer of material  806 . The second layer of material  806  includes an outer-facing surface  820  and an inner-facing surface  822 . 
     As shown in  FIG. 11 , a plurality of three-dimensional spacers  302  are disposed on the inner-facing surface  818  of the outer layer of material  802 , which is also referred to as the first layer of material and the outer-facing surface of the entire multi-layered structure. The plurality of three-dimensional spacers  302  define a plurality of channels  314  that are formed between the outer (first) layer of material  802  and the second layer of material  806 . Further, the plurality of three-dimensional spacers  302  create a forced separation or space between the inner-facing surface  818  of the outer (first) layer of material  802  and the outer-facing surface  820  of the second layer of material  806 . The separation between the outer-facing surface  820  of the second layer of material  806  and the inner-facing surface  818  of the outer (first) layer of material  802  spans a distance D, which is controlled at least in part by the maximum height S of the three-dimensional spacers  302 . In addition, a plurality of three-dimensional spacers  302  are also disposed on the inner-facing surface  812  of the inner (third) layer of material  808 , where the three-dimensional spacers  302  also define a plurality of channels  314 . Further, the plurality of three-dimensional spacers  302  present on the inner-facing surface  812  of the inner (third) layer of material  808  can create a forced separation between a user&#39;s skin and the inner (third) layer of material  808  to provide for added comfort to the user since the multi-layered structure  880  only contacts the user at the three-dimensional spacers  302  rather than across the entire inner-facing surface  812  as in the multi-layered structure  800  and  860 . The separation is controlled at least in part by the maximum height S of the three-dimensional spacers  302 . 
     In the specific embodiment of  FIG. 11 , the outer (first) layer of material  802  on which a plurality of three-dimensional spacers  302  are disposed and the inner (third) layer of material  808  are spunbond webs, while the second layer of material  806  positioned between them is a meltblown web. Further, in the specific embodiment of  FIG. 11 , the three-dimensional spacers  302  present on the inner-facing surface  818  of the (outer) first layer of material  802  are in the form of an acrylic binder, while the three-dimensional spacers  302  present on the inner-facing surface  812  of the inner (third) layer  808  are formed from a binder which contains an encapsulated phase change material so that the three-dimensional spacers  302  present on the inner-facing surface  812  not only minimize the degree of contact between the multi-layered structure  880  and the user, but can also facilitate additional cooling to the user. 
     The multi-layered structure  880  was tested for splash resistance according to ASTM Standard F-1862 (Level 3), where the fluid was prevented from passing through the meltblown (second) layer  806  due at least in part to the presence of three-dimensional spacers  302  present on the inner-facing surface  818  of the spunbond outer (first) layer of material  802 , which corresponds with the outermost layer of the multi-layered structure  880 . In other words, the multi-layered structure  880  of  FIG. 11  required only two layers of material (e.g., spunbond layer  802  having the three-dimensional spacers  302  present on its inner-facing surface  818  and meltblown layer  808 ) to prevent passage of fluid through the multi-layered structure, even though the multi-layered structure  880  was only three-layered. 
     Further,  FIG. 12  illustrates a three-layered structure  890  according to yet another embodiment of the present invention in which the spunbond layer  804  has been eliminated. The multi-layered structure  890  has three layers including an outer (first) layer of material  802  and an inner (third) layer of material  808 , where the outer (first) layer of material  802  includes an outer-facing surface  810  and an inner-facing surface  818 , and the inner (third) layer of material  808  includes an outer-facing surface  824  and an inner-facing surface  812 . Disposed between the outer (first) layer of material  802  and the inner (third) layer of material  808  is a second layer of material  806 . The layer of material  806  includes an outer-facing surface  820  and an inner-facing surface  822 . 
     As shown in  FIG. 12 , a plurality of three-dimensional spacers  302  are disposed on the inner-facing surface  822  of the second layer of material  806 . The plurality of three-dimensional spacers  302  define a plurality of channels  314  that are formed between the second layer of material  806  and the inner (third) layer of material  808 . Further, the plurality of three-dimensional spacers  302  create a forced separation or space between the inner-facing surface  822  of the second layer of material  806  and the outer-facing surface  824  of the inner (third) layer of material  808 . The separation between the inner-facing surface  822  of the second layer of material  806  and the outer-facing surface  824  of the inner (third) layer of material  808  spans a distance D, which is controlled at least in part by the maximum height S of the three-dimensional spacers  302 . In addition, a plurality of three-dimensional spacers  302  are also disposed on the inner-facing surface  812  of the inner (third) layer of material  808 , where the three-dimensional spacers  302  also define a plurality of channels  314 . Further, the plurality of three-dimensional spacers  302  present on the inner-facing surface  812  of the inner (third) layer of material  808  can create a forced separation between a user&#39;s skin and the inner (third) layer of material  808  to provide for added comfort to the user since the multi-layered structure  890  only contacts the user at the three-dimensional spacers  302  rather than across the entire inner-facing surface  812  as in the multi-layered structures  800  and  860 . The separation is controlled at least in part by the maximum height S of the three-dimensional spacers  302 . 
     In the specific embodiment of  FIG. 12 , the outer (first) layer of material  802  and the inner (third) layer of material  808  are spunbond webs, while the second layer of material  806  positioned between them and on which a plurality of three-dimensional spacers  302  are disposed is a meltblown web. Further, in the specific embodiment of  FIG. 12 , the three-dimensional spacers  302  present on the inner-facing surface  822  of the second layer of material  806  are in the form of an acrylic binder, while the three-dimensional spacers  302  present on the inner-facing surface  812  of the inner (third) layer  808  are formed from a binder which contains an encapsulated phase change material so that the three-dimensional spacers  302  present on the inner-facing surface  812  not only minimize the degree of contact between the multi-layered structure  890  and the user, but can also facilitate additional cooling to the user. 
     The multi-layered structure  890  was tested for splash resistance according to ASTM Standard F-1862 (Level 3), where the fluid was prevented from passing through the meltblown (second) layer  806  due at least in part to the presence of three-dimensional spacers  302  present on the inner-facing surface  822  of the meltblown (second) layer of material  806 . However, the splash resistance was not as good as that shown for the multi-layered structure  880 . In any event, the multi-layered structure  890  of  FIG. 12  still required only two layers of material (e.g., spunbond layer  802  and meltblown layer  806  having the three-dimensional spacers  302  present on its inner-facing surface  822 ) to prevent passage of fluid through the multi-layered structure, even though the multi-layered structure  890  was only three-layered. 
     For comparison,  FIG. 7  shows a four-layered structure  700  that does not include the three-dimensional spacers of the multi-layered structure of the present invention. The multi-layered structure has an outer layer of material  702  having an outer-facing surface  710  and an inner layer of material  708  having an inner-facing surface  712 , where the outer layer of material  702  is positioned furthest from the user and the inner layer of material  708  is positioned closest to the user, such as next to the skin. Between the outer layer of material  702  and the inner layer of material  708  are two additional layers  704  and  706 . The layer of material  704  is adjacent the outer layer of material  702 , while the layer of material  706  is adjacent the inner layer of material  708 . The outer layer of material  702 , the inner layer of material  708 , and the layer of material  704  adjacent the outer layer of material  702  can each be formed from a spunbond web, while the layer of material  706  adjacent the inner layer of material  708  can be a meltblown material. However, it is to be understood that any of the types of nonwoven web, foam, or film materials can be used to form such layers. 
     In any event, the multi-layered structure  700  was tested for splash resistance according to ASTM Standard F-1862 (Level 3), where the fluid was prevented from passing through the layer of material  706 , which is the third layer past the point of fluid contact at the outer-facing surface  710  of the outer layer of material  702 , meaning that the multi-layered structure  700  of  FIG. 7  required three layers (e.g., two spunbond layers  702 ,  704  and a meltblown layer  706 ) to prevent passage of fluid through the multi-layered structure. In contrast, the multi-layered structure of the present invention can prevent the passage of fluid through the multi-layered structure utilizing only one layer of material and the three-dimensional spacers discussed above, particularly when the three-dimensional spacers are adjacent a spunbond layer in the direction of the outer-facing surface or point of fluid contact. 
     In general, comparing  FIGS. 8-12  with  FIG. 7  shows that incorporating three-dimensional spacers on a layer of a three-layered structure or a four-layered structure can increase the splash resistance of such a structure so long as the three-dimensional spacers are postioned within the multi-layered structure (e.g., not on the outer-facing surface of the outer layer or the inner-facing surface of the inner layer). 
     Meanwhile,  FIG. 41  shows a three-layered structure  900  according to an additional embodiment of the present invention. The multi-layered structure  900  has three layers including an outer (first) layer of material  802  and an inner (third) layer of material  808 , where the outer (first) layer of material  802  includes an outer-facing surface  810  and an inner-facing surface  818 , and the inner (third) layer of material  808  includes an outer-facing surface  824  and an inner-facing surface  812 . Disposed between the outer (first) layer of material  802  and the inner (third) layer of material  808  is a second layer of material  806 . The second layer of material  806  includes an outer-facing surface  820  and an inner-facing surface  822 . 
     As shown in  FIG. 41 , a plurality of three-dimensional spacers  302  can be disposed on the inner-facing surface  818  of the outer layer of material  802 , which is also referred to as the first layer of material and the outer-facing surface of the entire multi-layered structure  900 . The plurality of three-dimensional spacers  302  define a plurality of channels  314  that are formed between the outer (first) layer of material  802  and the second layer of material  806 . Further, the plurality of three-dimensional spacers  302  create a forced separation or space between the inner-facing surface  818  of the outer (first) layer of material  802  and the outer-facing surface  820  of the second layer of material  806 . The separation between the outer-facing surface  820  of the second layer of material  806  and the inner-facing surface  818  of the outer (first) layer of material  802  spans a distance D, which is controlled at least in part by the maximum height S of the three-dimensional spacers  302 . 
     In addition, three-dimensional spacers in the form of encapsulated phase change material having portions  302   a ,  302   b , and  302   c  can be disposed on the inner (third) layer of material  808 , where the three-dimensional spacers are in thermal contact with both the outer-facing surface  824  and the inner-facing surface  812  of the inner (third) layer of material  808 . For instance, a plurality of three-dimensional spacers  302   a  are also disposed on the outer-facing surface  824  of the inner (third) layer of material  808 , where the three-dimensional spacers  302   a  also define a plurality of channels  315 . Further, the plurality of three-dimensional spacers  302   a  present on the outer-facing surface  824  of the inner (third) layer of material  808  can create a forced separation between the middle (second) layer of material  806  and the inner (third) layer of material  808 . The separation between the outer-facing surface  824  of the inner (third) layer of material  808  and the inner-facing surface  822  of the second layer of material  806  spans a distance D 1 , which is controlled at least in part by the maximum height S 1  of the three-dimensional spacers  302   a . Further, the three-dimensional spacers in the form of encapsulated phase change material can extend through the inner (third) layer of material  808  in the form of channels  302   c  and can also reside on the inner-facing surface  312  of the inner (third) layer of material  808  as three-dimensional spacers  302   b  having a height S 2 . As such, the phase change material saturates through the inner (third) layer of material  808  to create a continuous, thermal conduit  302   c  between spacers  302   a  and  302   b , where the three-dimensional spacers  302   a  present on the outer-facing surface  824  of the inner (third) layer of material  808  have a larger surface area than the three-dimensional spacers  302   b  present on the inner-facing surface  812  of the inner (third) layer of material  808 . In other words, the phase change material can be in thermal contact with both surfaces of the inner (third) layer of material  808  to facilitate cooling, even when a majority of the phase change material is present on the outer-facing surface  824  as opposed to the inner-facing (skin-facing) surface  812  of the third (inner) layer of material  808 . 
     Further, in one particular embodiment, the three-dimensional spacers  302   a  can be in contact with a surface area of the outer-facing surface  824  of the inner (third) layer of material  808  that is larger than the surface area of the three-dimensional spacers  302   b  that is in contact with the inner-facing surface  812  of the inner (third) layer of material  808 . As such, the amount of contact between the user&#39;s skin and the phase change material associated with the three-dimensional spacers  302   b  is reduced, yet the cooling effect is not decreased. In addition, such a configuration allows for improved manufacturing processes, as reduced amounts of the phase change material are lost when manufacturing a face mask with this configuration as opposed to a configuration where a majority of the phase change material is present on the inner-facing surface  812  of the inner (third) layer of material  808 . 
     In the specific embodiment of  FIG. 41 , the outer (first) layer of material  802  on which a plurality of three-dimensional spacers  302  are disposed and the inner (third) layer of material  808  are spunbond webs, while the second layer of material  806  positioned between them can be a meltblown web. Further, in the specific embodiment of  FIG. 41 , the three-dimensional spacers  302  present on the inner-facing surface  818  of the (outer) first layer of material  802  are in the form of an acrylic binder, while the three-dimensional spacers  302   a ,  302   b , and  302   c  present on the inner-facing surface  812  of the inner (third) layer  808  are formed from a binder which contains an encapsulated phase change material so that the three-dimensional spacers  302   a ,  302   b , and  302   c  present throughout the inner (third) layer of material  808  not only minimize the degree of contact between the multi-layered structure  900  and the user, but can also facilitate additional cooling to the user. 
     Turning now to  FIGS. 13 and 14 , a four-layered structure formed into a face mask is shown, where a polyester nonwoven layer on which three-dimensional spacers in the form of an encapsulated phase change material are disposed. As shown in  FIG. 14 , which is a cross-sectional view of the mask  600  of  FIG. 13  taken at cut line  14 - 14 , the mask  600  includes an outer layer of material  802  having an outer-facing surface  810  and an inner layer of material  808  having an inner-facing surface  812 , where the outer layer of material  802  is positioned furthest from the user and the inner layer of material  808  is positioned closest to the user, such as next to the skin. Between the outer layer of material  802  and the inner layer of material  808  are two additional layers  804  and  806 . The layer of material  804  is adjacent the outer layer of material  802 , while the layer of material  806  is adjacent the inner layer of material  708 . The outer layer of material  802 , the inner layer of material  808 , and the layer of material  804  adjacent the outer layer of material  802  can each be formed from a spunbond web, while the layer of material  806  adjacent the inner layer of material  808  can be a meltblown material. However, it is to be understood that any of the types of nonwoven web, foam, or film materials can be used to form such layers. 
     In any event, the mask  600  also includes an encapsulated phase change material that is positioned adjacent the inner layer of material  808 , where the encapsulated phase change material can be in the form of three-dimensional spacers  602  disposed on a substrate  610  that can include, for example, a nonwoven material. The nonwoven material can be any suitable material such as a polyolefin, polyester, a blend of natural fibers, or a combination thereof, etc. and can be a meltblown material, a spunbond material, an SMS laminate, a film, a spunlace material, etc. Further, the nonwoven material can be hydrophilic in order to facilitate the absorption and distribution of fluid in an efficient manner. However, it is also to be understood that the three-dimensional spacers  602  with phase change material can be applied directly on the inner-facing surface  812  of the inner layer  808  rather than on the substrate  610 . As shown in  FIGS. 13 and 14 , depending on the placement of the substrate  610  across the middle portion of the mask  600 , the substrate  610  or the inner layer  808  can form at least a part of the inner-facing (skin-contacting) surface  812  of the mask  600 . Further, a substrate border  603  can be present around the perimeter of the mask, where the substrate border  603  also includes a plurality of three-dimensional spacers  602  in the form of an encapsulated phase change material contained within a binder. The substrate border  603  can have a width of from about 0.5 millimeters to about 15 millimeters, such as from about 1 millimeter to about 10 millimeters, such as from about 1.5 millimeters to about 7.5 millimeters, while the center portion of the substrate  610  can have a length ranging from about 10 centimeters to about 20 centimeters, such as from about 12 centimeters to about 19 centimeters, such as from about 14 centimeters to about 18 centimeters and a width ranging from about 12 centimeters to about 22 centimeters, such as from about 14 centimeters to about 21 centimeters, such as from about 16 centimeters to about 20 centimeters. In some embodiments, either the border  603  or center portion of the substrate  610  may be absent from the mask  600 , while in some embodiments, both the substrate border  603  and the center portion of the substrate  610  are present. 
     Further, although the substrate is shown as covering about 75% of the total surface area of the inner-facing surface of the inner layer of material  808  of the mask  600  (including the center portion of the substrate  610  and the substrate border  603 ) in  FIG. 13 , it is to be understood that the nonwoven material including the phase change material or the phase change material alone can cover from about 10% to about 100%, such as from about 15% to about 100%, such as from about 30% to about 100%, such as from about 40% to about 100%, such as from about 50% to about 100% of the total surface area of the inner-facing surface of the inner layer of material  808  of the mask  600 . In other embodiments, the nonwoven material including the phase change material or the phase change material alone can cover from about 10% to about 70%, such as from about 15% to about 65%, such as from about 20% to about 60%, such as from about 25% to about 55% of the total surface area of the inner-facing surface of the inner layer of material  808  of the mask  600 . 
     Referring now to  FIG. 42 , in one more embodiment a four-layered structure formed into a face mask is shown, where a polyester nonwoven layer on which three-dimensional spacers in the form of an encapsulated phase change material are disposed. The face mask  650  can include any of the layers described in  FIGS. 13 and 14 . However, unlike the face mask  600  of  FIGS. 13 and 14 , the face mask  650  of  FIG. 42  can include substrates  610   a  and  610   b  positioned adjacent an upper edge  652  and a lower edge  654 , respectively, of the face mask  650 , where the substrates extend between the side edges  654  and  656  of the face mask  650 . The substrates  610   a  and  610   b  can each include an encapsulated phase change material that is positioned adjacent the inner layer of material  808 , where the encapsulated phase change material can be in the form of three-dimensional spacers  602  disposed on a substrate  610   a  or  610   b  that can include, for example, a nonwoven material. The nonwoven material can be any suitable material such as a polyolefin, polyester, a blend of natural fibers, or a combination thereof, etc. and can be a meltblown material, a spunbond material, an SMS laminate, a film, a spunlace material, etc. Further, the nonwoven material can be hydrophilic in order to facilitate the absorption and distribution of fluid in an efficient manner. However, it is also to be understood that the three-dimensional spacers  602  with phase change material can be applied directly on the inner-facing surface  812  of the inner layer  808  rather than on the substrate  610   a  or  610   b . As shown in  FIG. 42 , each substrate  610   a  and  610   b  can cover about 15% to about 30%, such as about 25%, of the surface area of the inner-facing surface  812  of the face mask  650 . 
     In addition, although shown as a series of discontinuous dots in  FIGS. 13, 14 , and  42 , the encapsulated phase change material can take any suitable shape such as lines, crosses, gridlines, logos, or any other form or shape. In addition, the center portion of the substrate  610  and substrate border  603  can be used in conjunction with any of the multi-layered structure embodiments shown in  FIGS. 8-12 and 41  and discussed in detail above. Without intending to be limited by any particular theory, discrete skin-contacting zones of phase change material, such as the phase change material present on the center portion of the substrate  610  and the border  603 , where phase change material is absent from other areas of the inner-facing surface  812  of the inner layer of material  808  can enhance the user&#39;s perception of cooling. In other words, the perception of a warm sensation on the skin that can be associated with the areas of the inner-facing surface  812  of the inner layer of material  808  on which no phase change material is present can amplify the cooling effect associated with the phase change material that is present on, for example, the border  603  or center portion of the substrate  610 . 
     Regardless of the particular arrangement of the multi-layered structures contemplated by the present invention, the various layers can be designed such that the thermal resistance of the face mask is reduced, where the thermal resistance can be reduced via conduction, convection, or both. As described above, face masks are made of polymeric materials. Because the polymers are insulators, heat can build up in the dead space of a face mask, leading to user discomfort. Heat is prevented from escaping from the dead space inside the face mask and accumulates inside the face mask. By reducing the thermal resistance of the face mask, the heat in the dead space can dissipate to improve user comfort. In particular, the layer of the face mask closest to the skin, such as the inner layer of material or substrate on which the three-dimensional spacers or phase change materials are deposited can have a reduced R-value (i.e., reduced thermal resistance). The R-value is a measure of resistance to heat flow through a given thickness of material. Thus, the higher the R-value, the more thermal resistance the material has and therefore the better its insulating properties. On the other hand, the lower the R-value, the less thermal resistance the material has and therefore the better it is able to transmit heat and the higher its conductivity. The R-value is calculated by using the formula:
 
 R -Value= I/λ 
 
where I is the thickness of the material in meters and λ is the thermal conductivity in W/mK. The R-value is measured in meters squared Kelvin per Watt (m 2 K/W).
 
     The R-value of the various layers of material in the face mask can be reduced by conduction by increasing the thermal conductivity of the various layers of material in the face mask, such as by incorporation of thermally conductive materials or structures into one or more layers of material used to form the face mask. For instance, metal particles, fibers, or inks including aluminum, gold, copper, silver, etc., conductive polymers, carbon, or any other material that can be used to increase thermal conductivity can be incorporated into or coated onto any layer of material of the multi-layered structure of the present invention. The thermally conductive materials or structures can be incorporated into the various layers of the face mask in any suitable pattern. For example, the thermally conductive materials or structures can be present in a continuous sheet, film, or coating on a layer of the face mask. Alternatively, the thermally conductive materials or structures can be present on a layer in a discontinuous pattern, a striped pattern (e.g., vertical or horizontal strips arranged on the layer), a grid, or any other pattern. In one particular embodiment, the thermally conductive materials or structures can be incorporated into the inner layer of the multi-layered structure (e.g., the layer closest to the skin and the layer on which the phase change material is deposited), the outer layer of the multi-layered structure, any other layer disposed therebetween, or a combination thereof. The use of such materials can facilitate the dissipation of heat from the inside of the face mask to the outside, preventing the buildup of heat in the dead space and minimizing user discomfort. 
     The R-value of the various layers of material in the face mask can be reduced by convection by incorporating materials (e.g., fibrous structures) that increase evaporative cooling into a particular layer of the multi-layered structure of the face mask, such as the inner layer (e.g., the layer closest to the skin and the layer on which the phase change material is deposited), the outer layer of the multi-layered structure, any other layer disposed therebetween, or a combination thereof. Materials that can be incorporated can include cotton fibers, rayon fibers, or any other fibers that can absorb and evaporate moisture. Such moisture absorptive and wicking fibrous structures can have varying surface topographies and shapes and can be in the form of nanofibers, channels, hollow fibers, etc. In addition, typically unwettable fibers (cellulosic materials, open cell foams, and fibrous foam laminates) can be used if treated with a wetting agent or surfactant or any other mechanism to facilitate the use of capillary action and absorption through the layer. The use of such materials to increase evaporative cooling can decrease the moisture level in the dead space of the mask between the user&#39;s skin and the inner layer, thus providing a cooling cycle for increased user comfort. 
     Regardless of the particular layer on which the thermally conductive materials or structures are incorporated or regardless of the particular layer that includes the materials that increase evaporative cooling, the mask can exhibit a reduced R-value compared to if no thermally conductive materials/structures or evaporative cooling materials are present within the various layers of the mask. For instance, the R-value or total thermal resistance of the mask can be less than about 0.15° ΔCm 2 /W, such as from about 0.04° ΔCm 2 /W to about 0.014° ΔCm 2 /W, such as from about 0.08° ΔCm 2 /W to about 0.10° ΔCm 2 /W. As a result of the reduced R-values attributed to the use of thermally conductive materials/structures and materials that enhance evaporative cooling, reduction in the temperature inside the dead space of the face masks that use the phase change materials of the present invention is enhanced. It should be noted that even small changes in mask temperature, such as between about 0.5° C. and about 1° C., are perceptible to the user because the facial skin can detect temperatures changes as small as 0.25° C. 
     The present invention may be better understood with reference to the following examples. 
     EXAMPLE 1 
     In Example 1, the temperature profiles for the microclimate inside the dead space of pleated face masks having a length of 17.5 centimeters and a width of 18.4 centimeters, where the inner-facing surface of the inner layer has a surface area of 0.032 m 2  and incorporating various configurations of an encapsulated phase change material disposed on a nonwoven polyester substrate, were recorded via thermal imaging and compared to a control mask that did not include an encapsulated phase change material, and the results are shown in the time lapse images shown in  FIGS. 15-17 . Specifically,  FIG. 15  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing the control face mask of Example 1, where no phase change material is present on the inner-facing surface of the inner layer of the face mask;  FIG. 16  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a pleated face mask as described in Example 1, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  around the perimeter of the inner-facing surface of the inner layer of the face mask and a rectangular section of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  in the center of the inner-facing surface of the inner layer of the face mask, where the nonwoven material with the encapsulated phase change material covers 30% of the surface area of the inner-facing surface of the inner layer of the face mask, resulting in a mask that includes about 101 Joules of phase change material; and  FIG. 17  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing pleated face mask as described in Example 1, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  around the perimeter of the inner-facing surface of the inner layer of the face mask and an oval section of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  in the center of the inner layer of the face mask, where the nonwoven material with the encapsulated phase change material covers 30% of the surface area of the inner layer of the face mask, resulting in a mask that includes about 101 Joules of phase change material. As shown, thermal images were recorded in pairs for inhaling (shown on the left) and exhaling (shown on the right) at the following times: 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, and 45 minutes. For all image recordings, the humidity of the environment was 60% and the temperature of the environment was 23.9° C. 
     Referring to  FIG. 15 , where no encapsulated phase change material was present, the inhalation temperature in the face mask microclimate ranges from 21.5° C. to 23.4° C. over the 45 minute time period, with the peak temperature of 23.4° C. occurring at 40 minutes. Meanwhile, the exhalation temperature in the face mask microclimate ranges from 26.7° C. to 29.4° C. over the 45 minute time period, with the peak temperature of 29.4° C. occurring at 40 minutes. 
     Referring to  FIG. 16 , where an encapsulated phase change material was present on a 6 millimeter border around the perimeter of the inner layer of the face mask and on a rectangular section that covered 30% of the surface area of the inner layer of the face mask, resulting in a mask that includes about 101 Joules of phase change material, the inhalation temperature in the face mask microclimate ranges from 23.1° C. to 24.7° C. over the 45 minute time period, with the peak temperature of 24.7° C. occurring at 5 minutes. Meanwhile, the exhalation temperature in the face mask microclimate ranges from 25.3° C. to 28.7° C. over the 45 minute time period, with the peak temperature of 28.7° C. occurring at 35 minutes. 
     Referring to  FIG. 17 , where an encapsulated phase change material was present on a 6 millimeter border around the perimeter of the inner layer of the face mask and an oval section that covered 30% of the surface area of the inner layer of the face mask, resulting in a mask that includes about 101 Joules of phase change material, the inhalation temperature in the face mask microclimate ranges from 24.2° C. to 26.3° C. over the 45 minute time period, with the peak temperature of 26.3° C. occurring at 30 minutes. Meanwhile, the exhalation temperature in the face mask microclimate ranges from 24.9° C. to 29.8° C. over the 45 minute time period, with the peak temperature of 29.8° C. occurring at 25 minutes. 
     In summary, the mask tested in  FIG. 16  showed immediate cooling to the face based on the beginning temperature and the presence of the blue cool image spots in the direct area (i.e., the mask border) where the encapsulated phase change material was placed during exhalation. Compared to the mask of  FIG. 17 , the mask of  FIG. 16  lowered the mask&#39;s microclimate temperature more consistently at a slower pace. In other words, the mask of  FIG. 16  was more effective due to its lower peak temperature (28.7° C.) and its ability to show a lower ending temperature (25.7° C.) over the total amount of time (3° C. difference from the peak temperature). Meanwhile, the mask tested in  FIG. 17  mask did not begin as cool, but cooled quickly within first 15 minutes, although the mask lost its effectiveness thereafter. The deciding factor of in selecting the appropriate phase change material is its ability to cool the body and absorb the higher heat temperatures over a longer amount of time. The mask of  FIG. 17  did not cool or absorb heat as well as the mask of  FIG. 16  based on the higher peak temperature (29.8° C.), as indicated by the images in  FIG. 17  having more red and yellow colors present as opposed to green and blue colors and the fact that the ending temperature was only lower than the peak high temperature 1.2° C. 
     EXAMPLE 2 
     In Example 2, the temperature profiles for the microclimate inside the dead space of several types of face masks incorporating various configurations of an encapsulated phase change material disposed on a nonwoven polyester substrate were recorded via thermal imaging and compared to a control mask that did not include an encapsulated phase change material, and the results are shown in the time lapse images shown in  FIGS. 18-40 . The pleated face masks tested in  FIGS. 18-27, 30-34, and 36-40  have a length of 17.5 centimeters and a width of 18.4 centimeters, where the inner-facing surface of the inner layer has a surface area of about 0.032 m 2 , while the inner-facing surface of the inner layer of the mask tested in  FIGS. 28 and 35  has a total surface area of about 0.023 m 2 , and the inner-facing surface of the inner layer of the mask tested in  FIG. 29  has a total surface area of about 0.0305 m 2 . Further, when a 6 millimeter border was used, the surface area of the border was about 0.00416 m 2  and the surface area of the center portion was about 0.028 m 2 . 
       FIG. 18  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing the control face mask of Example 2, where no phase change material is present on the face mask. 
       FIG. 19  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  around the perimeter of the face mask; 
       FIG. 20  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  around the perimeter of the face mask, where the border is in the form of two nonwoven layers, where each layer includes a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2 . 
       FIG. 21  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 16,000 Joules/m 2  around the perimeter of the face mask. 
       FIG. 22  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  around the perimeter of the face mask as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 30% of the surface area of the mask. 
       FIG. 23  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  around the perimeter of the face mask, where the border is in the form of two nonwoven layers, where each layer includes a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  phase change material, as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the material is in the form of two nonwoven layers, where each layer includes a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  phase change material, where the nonwoven material with the encapsulated phase change material covers 30% of the surface area of the mask. 
       FIG. 24  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 16,000 Joules/m 2  around the perimeter of the face mask as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 16,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 30% of the surface area of the mask. 
       FIG. 25  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 16,000 Joules/m 2  around the perimeter of the face mask as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the material is in the form of two nonwoven layers, where each layer includes a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  phase change material, where the nonwoven material with the encapsulated phase change material covers 30% of the surface area of the mask. 
       FIG. 26  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 16,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 30% of the surface area of the mask. 
       FIG. 27  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  around the perimeter of the face mask as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 30% of the surface area of the mask, where the nonwoven material is in the form of a single layer. 
       FIG. 28  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 30% of the surface area of the mask, where the face mask had an inner-facing layer having a total surface area of about 0.023 m 2 , which is about 30% less than the total surface area of the inner-facing surface of the pleated face masks tested in  FIGS. 18-27, 30-34, and 36-40 , which have a total surface area of their inner-facing layers of about 0.032 m 2 . 
       FIG. 29  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a nonwoven material containing a strip of foam that contains encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  positioned across a top portion of the inner-facing surface of the face mask, as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 30% of the surface area of the mask, where the inner-facing layer of the face mask had a total surface area of about 0.0305 m 2 . The foam helps to form a good seal to the bridge of the nose in conjunction with cooling air that tries to escape at the top of the mask, which improves the anti-fog properties of the mask. 
       FIG. 30  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 40 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  around the perimeter of the face mask as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 60% of the surface area of the mask. 
       FIG. 31  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  around the perimeter of the face mask as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 60% of the surface area of the mask. 
       FIG. 32  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 16,000 Joules/m 2  around the perimeter of the face mask as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 16,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 60% of the surface area of the mask. 
       FIG. 33  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 16,000 Joules/m 2  around the perimeter of the face mask as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 60% of the surface area of the mask. 
       FIG. 34  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 16,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 60% of the surface area of the mask. 
       FIG. 35  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 40 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 60% of the surface area of the mask, where the face mask had an inner-facing layer having a total surface area of about 0.023 m 2 . 
       FIG. 36  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  around the perimeter of the face mask as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 4,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 100% of the surface area of the mask. 
       FIG. 37  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  around the perimeter of the face mask as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 100% of the surface area of the mask. 
       FIG. 38  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 16,000 Joules/m 2  around the perimeter of the face mask as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 16,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 100% of the surface area of the mask. 
       FIG. 39  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a 6 millimeter border of a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 16,000 Joules/m 2  around the perimeter of the face mask as well as a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 8,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 100% of the surface area of the mask. 
       FIG. 40  illustrates a thermal imaging profile during inhaling (left) and exhaling (right) over a 45 minute period for a user wearing a face mask as described in Example 2, where the face mask includes a nonwoven material containing a discontinuous pattern of encapsulated phase change material having a heat of fusion of 16,000 Joules/m 2  positioned on a middle portion of the inner-facing surface of the face mask, where the nonwoven material with the encapsulated phase change material covers 100% of the surface area of the mask. 
     As shown, thermal images were recorded in pairs for inhaling (shown on the left) and exhaling (shown on the right) at the following times: 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, and 45 minutes (except no 45 minute images were recorded for the face masks of  FIGS. 30 and 35 ). For all image recordings, the humidity of the environment was 60% and the temperature of the environment was 23.9° C. The results for the various face mask configurations in  FIGS. 18-40  are shown below in Table 1. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Face Mask Temperatures at Inhalation and Exhalation Over Time 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                   
                   
                   
                 Time 
               
               
                   
                   
                 Mean 
                 Mean 
                 Difference between 
                 Lowest 
                 Peak 
                 of Peak 
               
               
                   
                   
                 Temperature 
                 Temperature 
                 Peak and Lowest 
                 Temperature 
                 Temperature 
                 Temperature 
               
               
                 FIG. 
                 Description 
                 Inhalation (° C.) 
                 Exhalation (° C.) 
                 Temperature (° C.) 
                 (° C.) 
                 (° C.) 
                 (Min.) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 18 
                 0.032 m 2  pleated mask control (no 
                 29.4 
                 32.6 
                 1.8 
                 32.1 
                 33.9 
                 5.0 
               
               
                   
                 PCM) 
               
               
                 19 
                 4,000 joule/m 2  6 mm border only; 
                 29.0 
                 33.1 
                 2.7 
                 31.6 
                 34.3 
                 30.0 
               
               
                   
                 0.032 m 2  pleated mask 
               
               
                 20 
                 8,000 joule/m 2  6 mm border only; 
                 27.4 
                 29.8 
                 2.7 
                 28.3 
                 31.0 
                 20.0 
               
               
                   
                 0.032 m 2  pleated mask 
               
               
                 21 
                 16,000 joule/m 2  6 mm border only; 
                 26.8 
                 31.5 
                 1.3 
                 31.0 
                 32.3 
                 35.0 
               
               
                   
                 0.032 m 2  pleated mask 
               
               
                 22 
                 4,000 joule/m 2  30% w/6 mm 
                 27.7 
                 31.6 
                 2.6 
                 30.3 
                 32.9 
                 10.0 
               
               
                   
                 border; 0.032 m 2  pleated mask 
               
               
                 23 
                 8,000 joule/m 2  30% w/6 mm 
                 27.9 
                 29.3 
                 2.1 
                 28.4 
                 30.5 
                 25.0 
               
               
                   
                 border; 0.032 m 2  pleated mask 
               
               
                 24 
                 16,000 joule/m 2  30% w/6 mm 
                 27.0 
                 29.6 
                 4.5 
                 27.4 
                 31.9 
                 35.0 
               
               
                   
                 border; 0.032 m 2  pleated mask 
               
               
                 25 
                 8,000 joule/m 2  30% w/16,000 joule/m 2   
                 26.6 
                 29.6 
                 2.9 
                 28.4 
                 31.3 
                 20.0 
               
               
                   
                 6 mm border; 0.032 m 2   
               
               
                   
                 pleated mask 
               
               
                 26 
                 500 joule 30% no border; 0.032 m 2   
                 28.2 
                 29.6 
                 1.5 
                 28.7 
                 30.2 
                 25.0 
               
               
                   
                 pleated mask 
               
               
                 27 
                 8,000 joule/m 2  30% w/6 mm 
                 28.0 
                 28.5 
                 1.5 
                 27.6 
                 29.1 
                 45.0 
               
               
                   
                 border; 0.032 m 2  pleated mask 
               
               
                 28 
                 4,000 joule/m 2  30% no border; 
                 27.2 
                 28.4 
                 1.9 
                 27.3 
                 29.2 
                 20.0 
               
               
                   
                 0.023 m 2  unpleated mask 
               
               
                 29 
                 4,000 joule/m 2  foam 30% no 
                 28.3 
                 28.6 
                 2.5 
                 27.4 
                 29.9 
                 20.0 
               
               
                   
                 border; 0.0305 m 2  unpleated mask 
               
               
                 30 
                 4,000 joule/m 2  60% w/6 mm 
                 28.5 
                 30.8 
                 1.1 
                 30.3 
                 31.4 
                 25.0 
               
               
                   
                 border; 0.032 m 2  pleated mask 
               
               
                 31 
                 8,000 joule/m 2  60% w/6 mm 
                 26.8 
                 29.0 
                 1.7 
                 28.0 
                 29.7 
                 35.0 
               
               
                   
                 border; 0.032 m 2  pleated mask 
               
               
                 32 
                 16,000 joule/m 2  60% w/6 mm 
                 26.7 
                 28.6 
                 2.3 
                 27.8 
                 30.1 
                 10.0 
               
               
                   
                 border; 0.032 m 2  pleated mask 
               
               
                 33 
                 8,000 joule/m 2  60% w/16,000 joule/m 2   
                 26.4 
                 28.7 
                 3.5 
                 27.5 
                 31.0 
                 45.0 
               
               
                   
                 6 mm border; 0.032 m 2   
               
               
                   
                 pleated mask 
               
               
                 34 
                 16,000 joule/m 2  60% no border; 
                 28.2 
                 29.4 
                 1.8 
                 28.6 
                 30.4 
                 45.0 
               
               
                   
                 0.032 m 2  pleated mask 
               
               
                 35 
                 4,000 joule/m 2  60% no border; 
                 27.5 
                 29.2 
                 1.7 
                 28.5 
                 30.2 
                 5.0 
               
               
                   
                 0.023 m 2  unpleated mask 
               
               
                 36 
                 4,000 joule/m 2  100% w/6 mm 
                 28.8 
                 29.2 
                 1.2 
                 28.7 
                 29.9 
                 15.0 
               
               
                   
                 border; 0.032 m 2  pleated mask 
               
               
                 37 
                 8,000 joule/m 2  100% w/6 mm 
                 26.6 
                 28.7 
                 2.8 
                 27.1 
                 29.9 
                 45.0 
               
               
                   
                 border; 0.032 m 2  pleated mask 
               
               
                 38 
                 16,000 joule/m 2  100% w/6 mm 
                 27.4 
                 28.3 
                 1.3 
                 27.8 
                 29.1 
                 30.0 
               
               
                   
                 border; 0.032 m 2  pleated mask 
               
               
                 39 
                 8,000 joule/m 2  100% w/16,000 joule/m 2   
                 27.1 
                 28.9 
                 3.3 
                 27.5 
                 30.8 
                 45.0 
               
               
                   
                 6 mm border; 0.032 m 2   
               
               
                   
                 pleated mask 
               
               
                 40 
                 16,000 joule/m 2  100% no border; 
                 28.0 
                 28.8 
                 3.4 
                 27.4 
                 30.8 
                 45.0 
               
               
                   
                 0.032 m 2  pleated mask 
               
               
                   
               
            
           
         
       
     
     Upon a review of  FIGS. 18-40  and Table 1 of Example 2, the data shows that the nonwoven polyester layer with encapsulated phase change material can reduce the temperature of the dead space within the microclimate of a face mask at exhalation by 1.3° C. to 4.5° C., where the masks having just a border of the nonwoven polyester/encapsulated phase change material had the lowest decrease in temperature. 
     Further, according to test user input, the 4,000 Joules/m 2  phase change material face masks having the nonwoven polyester/phase change material cover 30% ( FIG. 22 ), 60% ( FIG. 30 ), and 100% ( FIG. 36 ) of the surface area of the inner layer of the face masks for the pleated design did not have noticeable cooling compared to the control mask of  FIG. 18 . 
     Meanwhile, the 8,000 Joules/m 2  phase change material face masks having the nonwoven polyester/phase change material cover 30% ( FIG. 23 ), 60% ( FIG. 31 ), and 100% ( FIG. 37 ) of the surface area of the inner layer of the face masks for the pleated design exhibited noticeable cooling compared to the control mask of  FIG. 18 . Further, the 16,000 Joules/m 2  phase change material face masks having the nonwoven polyester/phase change material cover 30% ( FIG. 24 ), 60% ( FIG. 32 ), and 100% ( FIG. 38 ) of the surface area of the inner layer of the face masks for the pleated design exhibited an immediate and noticeable coolness greater than the 4,000 Joules/m 2  and 8,000 Joules/m 2  masks but for an overall time frame that performed similar to the 8,000 Joules/m 2  mask. Additionally, the overall perception of the 16,000 Joules/m 2  mask was the same as the 8,000 Joules/m 2  mask, although the immediate coolness of the 16,000 Joules/m 2  mask was more noticeable when first donning the mask. 
     In addition, the 4,000 Joules/m 2  phase change material masks having an inner-facing layer having a smaller total surface area of 0.023 m 2  (compared to the 0.032 m 2  total surface area of the inner-facing layers of the masks of  FIGS. 18-27, 30-34, and 36-40 ) and having the nonwoven polyester/phase change material cover 30% ( FIG. 28 ) and 60% ( FIG. 35 ) of the surface area of the inner layer of the face masks for the unpleated design were perceived by users as having more breathability and a better fit, while still feeling cool. 
     Moreover, the 4,000 Joules/m 2  unpleated bio-mask having an inner-facing layer having a slightly smaller total surface area of 0.0305 m 2  (compared to the 0.032 m 2  total surface area of the inner-facing layers of the masks of  FIGS. 18-27, 30-34, and 36-40 ) and having the nonwoven polyester/phase change material cover 30% ( FIG. 29 ) of the surface area of the inner layer of the face masks for the unpleated design was perceived by users as feeling cool and having a better fit, where the foam PCM was cool while reducing the amount of hot air rising that usually produces fog on eyewear or a visor worn in conjunction with the mask. 
     Next, the amount of the phase change material layer present on the various masks of  FIGS. 18-40  was calculated based on the inner-facing layer of to determine how many Joules of energy the phase change material needed to be present to provide for sufficient cooling of the mask microclimate when worn. The results are summarized in Table 2. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Distribution of Phase Change Material Layer on the Inner-Facing Layer of 
               
               
                 the Masks of FIGS. 18-40 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                   
                   
                 % Surface 
               
               
                   
                   
                 Surface Area of 
                   
                   
                   
                 Area of Inner- 
               
               
                   
                   
                 Inner-Facing 
                 Surface Area of 
                 Joules of PCM on 
                 Joules/m 2  of 
                 Facing 
               
               
                   
                   
                 Surface of Mask 
                 PCM NW Layer 
                 Inner-Facing 
                 PCM on Inner- 
                 Surface 
               
               
                 FIG. 
                 Description 
                 Inner Layer (m 2 ) 
                 (m 2 ) 
                 Surface of Mask 
                 Facing Surface 
                 Covered 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 18 
                 0.032 m 2  pleated mask control (no 
                 0.032 
                 0.0 
                 0.0 
                 0.0 
                 0.0 
               
               
                   
                 PCM) 
               
               
                 19 
                 4,000 joule/m 2  6 mm border only; 
                 0.032 
                 0.004 
                 17 
                 521 
                 13.0 
               
               
                   
                 0.032 m 2  pleated mask 
               
               
                 20 
                 8,000 joule/m 2  6 mm border only; 
                 0.032 
                 0.004 
                 33 
                 1041 
                 13.0 
               
               
                   
                 0.032 m 2  pleated mask 
               
               
                 21 
                 16,000 joule/m 2  6 mm border only; 
                 0.032 
                 0.004 
                 67 
                 2082 
                 13.0 
               
               
                   
                 0.032 m 2  pleated mask 
               
               
                 22 
                 4,000 joule/m 2  30% w/6 mm 
                 0.032 
                 0.013 
                 50 
                 1572 
                 39.3 
               
               
                   
                 border; 0.032 m 2  pleated mask 
               
               
                 23 
                 8,000 joule/m 2  30% w/6 mm 
                 0.032 
                 0.013 
                 101 
                 3144 
                 39.3 
               
               
                   
                 border; 0.032 m 2  pleated mask 
               
               
                 24 
                 16,000 joule/m 2  30% w/6 mm 
                 0.032 
                 0.013 
                 201 
                 6288 
                 39.3 
               
               
                   
                 border; 0.032 m 2  pleated mask 
               
               
                 25 
                 8,000 joule/m 2  30% w/16,000 joule/m 2   
                 0.032 
                 0.013 
                 134 
                 4161 
                 39.1 
               
               
                   
                 6 mm border; 0.032 m 2   
               
               
                   
                 pleated mask 
               
               
                 26 
                 16,000 joule/m 2  30% no border; 
                 0.032 
                 0.008 
                 135 
                 4179 
                 26.1 
               
               
                   
                 0.032 m 2  pleated mask 
               
               
                 27 
                 8,000 joule/m 2  30% w/6 mm 
                 0.032 
                 0.013 
                 101 
                 3124 
                 39.1 
               
               
                   
                 border; 0.032 m 2  pleated mask 
               
               
                 28 
                 4,000 joule/m 2  30% no border; 
                 0.023 
                 0.007 
                 28 
                 1200 
                 30.0 
               
               
                   
                 0.023 m 2  unpleated mask 
               
               
                 29 
                 4,000 joule/m 2  foam 30% no 
                 0.0305 
                 0.009 
                 37 
                 1200 
                 30.0 
               
               
                   
                 border; 0.0305 m 2  unpleated mask 
               
               
                 30 
                 4,000 joule/m 2  60% w/6 mm 
                 0.032 
                 0.021 
                 84 
                 2607 
                 65.2 
               
               
                   
                 border; 0.032 m 2  pleated mask 
               
               
                 31 
                 8,000 joule/m 2  60% w/6 mm 
                 0.032 
                 0.021 
                 168 
                 5214 
                 65.2 
               
               
                   
                 border; 0.032 m 2  pleated mask 
               
               
                 32 
                 16,000 joule/m 2  60% w/6 mm 
                 0.032 
                 0.021 
                 336 
                 10428 
                 65.2 
               
               
                   
                 border; 0.032 m 2  pleated mask 
               
               
                 33 
                 8,000 joule/m 2  60% w/16,000 joule/m 2   
                 0.032 
                 0.021 
                 201 
                 6242 
                 65.2 
               
               
                   
                 6 mm border; 0.032 m 2   
               
               
                   
                 pleated mask 
               
               
                 34 
                 16,000 joule/m 2  60% no border; 
                 0.032 
                 0.017 
                 269 
                 8359 
                 52.2 
               
               
                   
                 0.032 m 2  pleated mask 
               
               
                 35 
                 4,000 joule/m 2  60% no border; 
                 0.023 
                 0.014 
                 55 
                 2400 
                 60.0 
               
               
                   
                 0.023 m 2  unpleated mask 
               
               
                 36 
                 4,000 joule/m 2  100% w/6 mm 
                 0.032 
                 0.032 
                 129 
                 4000 
                 100.0 
               
               
                   
                 border; 0.032 m 2  pleated mask 
               
               
                 37 
                 8,000 joule/m 2  100% w/6 mm 
                 0.032 
                 0.032 
                 258 
                 8000 
                 100.0 
               
               
                   
                 border; 0.032 m 2  pleated mask 
               
               
                 38 
                 16,000 joule/m 2  100% w/6 mm 
                 0.032 
                 0.032 
                 515 
                 16000 
                 100.0 
               
               
                   
                 border; 0.032 m 2  pleated mask 
               
               
                 39 
                 8,000 joule/m 2  100% w/16,000 joule/m 2   
                 0.032 
                 0.032 
                 291 
                 9037 
                 100.0 
               
               
                   
                 6 mm border; 0.032 m 2   
               
               
                   
                 pleated mask 
               
               
                 40 
                 16,000 joule/m 2  100% no border; 
                 0.032 
                 0.028 
                 449 
                 13931 
                 87.1 
               
               
                   
                 0.032 m 2  pleated mask 
               
               
                   
               
            
           
         
       
     
     Based on user input with respect to the masks of  FIGS. 18-40 , the minimum threshold of Joules needed for sufficient cooling is 101 Joules, optimally, spread out between the border and the center of the inner layer of the mask. Further, if the phase change material layer is only present on the border of the mask, at least about 66 Joules of cooling are needed, and such a level provides only temporary comfort. Moreover, it should be noted that the amount of Joules needed for cooling can be decreased by improving the fit of the mask so that more of the phase change material is in contact with the skin and the void volume of air within the mask is decreased. 
     EXAMPLE 3 
     In Example 3, a multi-layered structure generally corresponding to the arrangement shown in  FIG. 9  (Control Sample) but without the three-dimensional spaces  302  was compared to a multi-layered structure arranged as shown in  FIG. 9  (Test Sample) for their ability to achieve Level 3 performance, which is the most stringent level of testing in ASTM F2100-11, where a face mask must resist splashes of 2 milliliters of synthetic blood (available from Johnson, Moen &amp; Co., 2505 Northridge Lane NE, Rochester, Minn. 55906) at 160 mmHg per the ASTM F1862-13 procedure. In other words, the control sample included the four-layered structure  860  except for the three-dimensional spacers  302 . The control sample multi-layered structure had an outer layer of material  802  formed from a polyester pulp wetlaid material having a basis weight of 0.5 ounces per square yard (16.95 gsm) and having an outer-facing surface  810 . The control sample multi-layered structure  860  also included an inner layer of material  808  formed from a bicomponent carded nonwoven material having a basis weight of 0.5 ounces per square yard (16.95 gsm) and having an inner-facing surface  812 , where the outer layer of material  802  was positioned closest to the fluid insult and the inner layer of material  808  was positioned furthest from the fluid insult, such as would be the case if the structure was used in a face mask worn next to the skin. Between the outer layer of material  802  and the inner layer of material  808  were two additional layers  804  and  806 . The layer of material  806  was positioned adjacent the outer layer of material  802  and was formed from a meltblown material having a basis weight of 0.6 ounces per square yard (20.34 gsm), while the layer of material  804  was positioned adjacent the inner layer of material  808  and was formed from a spunbond material having a basis weight of 0.9 ounces per square yard (30.52 gsm). 
     Meanwhile, the test sample generally corresponded with the multi-layered structure  860  of  FIG. 9 . In particular, the test sample included an outer layer of material  802  formed from a polyester pulp wetlaid material having a basis weight of 0.5 ounces per square yard (16.95 gsm) and an inner layer of material  808  formed from a bicomponent carded nonwoven material having a basis weight of 0.5 ounces per square yard (16.95 gsm), where the outer layer of material  802  included an outer-facing surface  810  and an inner-facing surface  818 , and the inner layer of material  808  included an outer-facing surface  824  and an inner-facing surface  812 . Disposed between the outer layer of material  802  and the inner layer of material  808  were a layer of material  806  and a layer of material  804 . The layer of material  806  was positioned adjacent the outer layer of material  802  and was formed from a meltblown material having a basis weight of 0.6 ounces per square yard (20.34 gsm), where the layer of material  806  included an outer-facing surface  820  and an inner-facing surface  822 . Meanwhile, the layer of material  804  was positioned adjacent the inner layer of material  808  and was formed from a spunbond material having a basis weight of 0.9 ounces per square yard (30.52 gsm), where the layer of material  804  included an outer-facing surface  814  and an inner-facing surface  816 . As shown in  FIG. 9 , a plurality of three-dimensional spacers  302  (i.e., dots) formed from an acrylic binder were also disposed on the outer-facing surface  814  of the layer of material  804 , which is also referred to as the third layer of material present past the outer-facing surface  810  of the outer layer of material  802 . The plurality of three-dimensional spacers  302  formed a plurality of channels  314  between the layer of material  806  and the layer of material  804 . Further, the plurality of three-dimensional spacers  302  created a forced separation or space between the outer-facing surface  814  of the third layer of material  804  and the inner-facing surface  822  of the second layer of material  806 . 
     The control sample and the test sample as described above were tested for splash resistance according to ASTM Standard F-1862 (Level 3), where the fluid passed through to the layer  808  in the Control Sample, meaning that the control sample failed ASTM Standard F-1862 (Level 3). However, the fluid did not pass through the layer  808  in the test sample, and thus the test sample passed ASTM Standard F-1862 (Level 3). 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.