Devices and methods for the production of microfibers and nanofibers

Described herein are apparatuses and methods of creating fibers, such as microfibers and nanofibers, that include additives that modify one or more properties of the produced fibers. The methods discussed herein employ centrifugal forces to transform material into fibers. Apparatuses that may be used to create fibers are also described. Fiber producing devices with features that enhance fiber production and adaptability to different types of fiber are described.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to the field of fiber production. More specifically, the invention relates to fibers of micron and sub-micron size diameters.

2. Description of the Relevant Art

Fibers having small diameters (e.g., micrometer (“micron”) to nanometer (“nano”)) are useful in a variety of fields from the clothing industry to military applications. For example, in the biomedical field, there is a strong interest in developing structures based on nanofibers that provide scaffolding for tissue growth to effectively support living cells. In the textile field, there is a strong interest in nanofibers because the nanofibers have a high surface area per unit mass that provide light, but highly wear resistant, garments. As a class, carbon nanofibers are being used, for example, in reinforced composites, in heat management, and in reinforcement of elastomers. Many potential applications for small-diameter fibers are being developed as the ability to manufacture and control their chemical and physical properties improves.

It is well known in fiber manufacturing to produce extremely fine fibrous materials of organic fibers, such as described in U.S. Pat. Nos. 4,043,331 and 4,044,404, where a fibrillar mat product is prepared by electrostatically spinning an organic material and subsequently collecting spun fibers on a suitable surface; U.S. Pat. No. 4,266,918, where a controlled pressure is applied to a molten polymer which is emitted through an opening of an energy charged plate; and U.S. Pat. No. 4,323,525, where a water soluble polymer is fed by a series of spaced syringes into an electric field including an energy charged metal mandrel having an aluminum foil wrapper there around which may be coated with a PTFE (Teflon™) release agent. Attention is further directed to U.S. Pat. Nos. 4,044,404, 4,639,390, 4,657,743, 4,842,505, 5,522,879, 6,106,913 and 6,111,590—all of which feature polymer nanofiber production arrangements.

Electrospinning is a major manufacturing method to make nanofibers. Examples of methods and machinery used for electrospinning can be found, for example, in the following U.S. Pat. Nos. 6,616,435; 6,713,011; 7,083,854; and 7,134,857.

SUMMARY OF THE INVENTION

Described herein are apparatuses and methods of creating fibers, such as microfibers and nanofibers. The methods discussed herein employ centrifugal forces to transform material into fibers.

In an embodiment, a device for use in a microfiber and/or nanofiber producing system includes: a substantially circular body, wherein a diameter of the body varies between a top surface of the body and a bottom surface of the body, an internal cavity disposed in the body, wherein the internal cavity receives material to be produced into a fiber, one or more openings that allow material to be passed from the internal cavity to the exterior of the body; and a coupling member, wherein the body is couplable to a driver through the coupling member. During use rotation of the body causes material in the body cavity to be passed through one or more openings and ejected from one or more material outlets to produce microfibers and/or nanofibers.

In an embodiment, a system for producing microfibers and/or nanofibers includes: a fiber producing device comprising a body, the body comprising one or more openings, and a coupling member, wherein the body is configured to receive material to be produced into a fiber; one or more temperature sensors disposed within the body or on a surface of the body; a driver capable of rotating the body, wherein the body is couplable to the driver through the coupling member; a shaft coupling the body to the drive; and a rotary electric device coupled to the shaft and electrically coupled to the sensors and a power source, wherein the rotary electric coupling provides and receives electrical signals to and from one or more of the temperature sensors while the fiber producing device is being rotated. During use rotation of the body causes material in the body to be passed through one or more openings to produce microfibers and/or nanofibers.

In an embodiment, a device for use in a microfiber and/or nanofiber producing system includes: a sidewall member, wherein one or more openings extend through the sidewall; a bottom member; and a top member; wherein the top member comprises a coupling member; and wherein the top member, the bottom member, and sidewall member define an internal cavity of the body, and wherein the sidewall is removable from the body. The body is configured to receive material to be produced into a fiber, and wherein the body is couplable to a driver through the coupling member. During use, rotation of the body causes material in the body to be passed through one or more openings to produce microfibers and/or nanofibers.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The terms “comprise” (and any form of comprise, such as “comprises” and “comprising”), “have” (and any form of have, such as “has” and “having”), “include” (and any form of include, such as “includes” and “including”) and “contain” (and any form of contain, such as “contains” and “containing”) are open-ended linking verbs. As a method or apparatus that “comprises,” “has,” “includes” or “contains” one or more steps or elements possesses those one or more steps or elements, but is not limited to possessing only those one or more steps or elements. Likewise, an element of an apparatus that “comprises,” “has,” “includes” or “contains” one or more features possesses those one or more features, but is not limited to possessing only those one or more features.

Described herein are apparatuses and methods of creating fibers, such as microfibers and nanofibers. The methods discussed herein employ centrifugal forces to transform material into fibers. Apparatuses that may be used to create fibers are also described. Some details regarding creating fibers using centrifugal forces may be found in the following U.S. Published Patent Applications: 2009/0280325 entitled “Methods and Apparatuses for Making Superfine Fibers” to Lozano et al.; 2009/0269429 entitled “Superfine Fiber Creating Spinneret and Uses Thereof” to Lozano et al.; 2009/0232920 entitled “Superfine Fiber Creating Spinneret and Uses Thereof” to Lozano et al.; 2009/0280207 entitled “Superfine Fiber Creating Spinneret and Uses Thereof” to Lozano et al.; 2012/0292810 entitled “Apparatuses Having Outlet Elements and Methods for the Production of Microfibers and Nanofibers” to Peno; 2012/0294966 entitled “Multilayer Apparatuses and Methods for the Production of Microfibers and Nanofibers” to Peno et al.; 2012/0295021 entitled “Apparatuses and Methods for the Deposition of Microfibers and Nanofibers on a Substrate” to Peno et al.; 2012/0292795 to entitled “Apparatuses and Methods for Simultaneous Production of Microfibers and Nanofibers” to Peno et al.; 2012/0304613 entitled “Split Fiber Producing Devices and Methods for the Production of Microfibers and Nanofibers” to Peno et al.; and 2012/0292796 entitled “Devices and Methods for the Production of Coaxial Microfibers and Nanofibers” to Peno et al.; all of which are incorporated herein by reference.

One embodiment of a fiber producing device is shown inFIGS. 3A-C. Fiber producing device100includes a body comprising a first member110(FIG. 38A) and a second member120(FIG. 38B). First member110includes a first member coupling surface112. First member coupling surface112includes one or more grooves114extending along the width of the first member coupling surface. Second member120includes a second member coupling surface122and a coupling member128. Second member coupling surface122comprises one or more grooves124extending along the width of the second member coupling surface. Coupling member128may be used to couple the body to a driver of a fiber producing system.

The body is formed by coupling first member110to second member120. To couple the first and second members, first member coupling surface112is contacted with second member coupling surface122. One or more fasteners130may be used to secure the first member and second member together. When the first member coupling surface is coupled to the second member coupling surface to form the body, the first member and the second member together define an internal cavity of the body. In one embodiment, fasteners130have an effect on the pattern of fiber produced by the fiber producing device. For example, the head of a fastener produces external gas currents due to the high speed of rotation of the fiber producing device. Additional components may be added on either side of the body or incorporated directly onto the surface of the body to produce external gas currents. These external gas currents can effect the pattern of fibers produced. The pattern of fibers produced by the fiber producing device may be altered by using fasteners having different head configurations. Alternatively, the position of fasteners may be altered to change the fiber deposition pattern. For example, the one or more fasteners may be left out of existing holes. Alternatively, the body may include a plurality of holes. The pattern of fibers produced by the fiber producing device may be altered by changing which of the plurality of holes are used to couple the first and second members together. In another embodiment. The height of the fasteners may be altered by loosing and or tightening the fasteners. Thus the height of the head of one or more fasteners may be varied to alter the pattern of fibers produced by the fiber producing device.

In some embodiments, it is desirable that grooves114of the first member are substantially aligned with groves124of the second member. When the grooves are aligned, the grooves together form one or more openings150extending from the interior cavity to an outer surface of the body. During use, rotation of the body material disposed in the internal cavity of the body is ejected through one or more openings150to produce microfibers and/or nanofibers. Material may be placed into the body of fiber producing through a first member opening128formed in first member110. In one embodiment, first member is ring shaped and material is added to the internal cavity through a central opening of the ring shaped first member.

In order to ensure proper alignment of the first member with the second member, the first member may include a first alignment element116disposed on the first coupling member surface112. The second member may include a second alignment element126disposed on the second member coupling surface122. First alignment element116couples with second alignment element126when first member110is properly aligned with second member120. This may help to ensure that grooves114and124are properly aligned. In one embodiment, one of the first or second alignment elements includes a projection extending form the coupling surface, and the other of the first or second alignment elements includes an indentation complementary to the projection.

In an embodiment, the first alignment element may be a first alignment ring116disposed on the first coupling member surface112. The second member may include a second alignment ring126disposed on the second member coupling surface122. First alignment ring116interlocks with second alignment ring126when first member110is properly aligned with second member120. The interlocking first and second rings center the first member and second member with each other. In one embodiment, first and second rings interlock with each other on an angle so that the first and second members are centered to one another. Alignment is further insured by the use of a projection140formed in the first member which fits into a suitable indentation145formed in the second member. Projection140and indentation145help ensure that the first and second members are coupled in the same rotational position such that the grooves of the first and second members are aligned.

In an embodiment, where the fiber producing device is coupled to a driver positioned above the fiber producing device, the coupling member extends through the internal cavity defined by the first and second members and through the first member. Alternatively, where the fiber producing device is coupled to a driver positioned below the fiber producing device, the coupling member is coupled to an outer surface of the second member, extending away from the second member.

In some embodiments, a fiber producing device may include a body. The body may be formed such that a portion of the body may function to facilitate conveyance of produced fibers away from the body. For example, the body of a fiber producing device may include draft members which create a gas flow proximate to the fiber producing device. In some embodiments, a fiber producing device may include two or more draft members. In some embodiments, a fiber producing device may include four draft members.FIGS. 2A-Band3A-B depict embodiments of a body of a fiber producing device with draft members. Draft members may function as blades on a fan creating a gas current. The gas current created by the draft members may facilitate movement of the produced fibers away from the fiber producing device. The gas currents may direct the produced fibers in a fiber producing system. In some embodiments, draft members may be angled out of the plane of the body of the fiber producing device. Draft members may be angled, much like blades of a fan, increasing the strength of a gas current produced by the draft members. In some embodiments, an angle of the draft members may be adjusted by a user in order to increase/decrease a strength of the gas current produced during use. Upon adjustment the draft members may be locked into place.

FIGS. 2A-Bdepict embodiments of a body of a fiber producing device200with draft members212positioned within an exterior ring portion214of the body of the fiber producing device. Channel216may function as a material input channel, wherein material is positioned in the channel before being spun out of openings in ring portion214and produced into fibers. As depicted in the cross section ofFIG. 2B, exterior ring portion214may include an inclined pressure channel220which functions to increase the pressure of material as the material is forced out the openings in the ring portion. Inclined pressure channel220may include a narrowing of the channel which then widens out before the openings.

Coupling member218may function to couple fiber producing device200to a drive system of a fiber producing system. In some embodiments, a top surface of exterior ring portion214may be compatible with an inductive heating system.

FIGS. 3A-Bdepict an alternate embodiment of a fiber producing device300with draft members312positioned outside of a ring portion314of the body of the fiber producing device. Channel316may function as a material input channel, wherein material is positioned in the channel before being spun out of openings in members312and produced into fibers. As depicted in the cross section ofFIG. 3B, draft members312may include a channel322. Channels322may function to connect openings324with channel316to produce fibers during use. In some embodiments, the body may be formed from layers of insulating material326and heat transmitting material328. Coupling member318may function to couple fiber producing device300to a drive system of a fiber producing system. In some embodiments, a top surface of exterior ring portion314may be compatible with an inductive heating system.

FIGS. 4A-Cdepict an alternate embodiment of a body of a fiber producing device400with a plurality of external draft members412. In the depicted embodiment fiber producing device400includes draft members412positioned outside of a ring portion414of the body of the fiber producing device. In the depicted embodiment, draft members412are coupled to ring portion414and a support member430. Channel416may function as a material input channel, wherein material is positioned in the channel (e.g., injected from a nozzle delivery system) before being spun out of openings in members412and produced into fibers. As depicted in the cross section ofFIG. 4B, draft members412may include a channel422. Channels422may function to connect openings424with channel416to produce fibers during use. Coupling member418may function to couple fiber producing device400to a drive system of a fiber producing system. In some embodiments, a top surface of the fiber producing device is compatible with an inductive heating system.

FIG. 4Cdepicts an embodiment of a body of a fiber producing device400with a plurality of external draft members412with a representation of air/fiber flow432during use. Draft members412are coupled to support member430forming a pattern which resembles an impeller. The plurality of support members are positioned at an angle radiating out from ring portion414. Material may be injected into channel416and then flow through channels422in draft members412due to the centrifugal forces resulting from fiber producing device400rotating at high speeds. Material may then be ejected through openings424(e.g., located at the end of the draft members), resulting from the centrifugal forces, producing the fibers. The draft members produce, during use, an air current or flow which pushes the produced fibers away from fiber producing device440(e.g., as depicted inFIG. 4C).

In another embodiment, a fiber producing device includes a body having one or more openings, a body cavity, and a coupling member. The body cavity is configured to receive material to be produced into a fiber. In some embodiments the body further comprising one or more gas outlets positioned proximate to the one or more openings. During use, rotation of the body causes material in the body cavity to be passed through one or more openings and ejected from one or more openings to produce microfibers and/or nanofibers, and wherein during rotation of the body, gas is passed through the gas outlets. An embodiment of a fiber producing device having such a configuration is depicted inFIG. 5. Fiber producing device500, includes one or more openings510passing through the sidewalls of the body and one or more gas outlets520positioned proximate to one or more openings. During use, gas is ejected through one or more of the gas outlets520, while material is ejected through one or more of the openings510. The ejected gas can guide the ejected material away from the fiber producing device to assist with the formation of fibers. The gas outlets may be positioned above and below the openings, as depicted inFIG. 5, or may be positioned on the centerline of the fiber producing body in between openings. Gas outlets may be employed in numbers greater than 2 per opening and arranged in circular or other patterns around the openings to optimize fiber formation. In some embodiments, the gas outlet can take the form of a annulus around the orifice.

Fiber producing device500includes a coupling member530which couples the fiber producing device to a driver. Coupling member530may include a central conduit which extends through coupling member530into the body of fiber producing device530. Central conduit may be used to introduce material directly into the body of fiber producing device500. In some embodiments, central conduit may also include a gas inlet that allows inert gas to be passed into the fiber producing device. Central conduit may include two or more lumens which are coupled to the fiber producing device. A first lumen may be used to introduce material into the body to be converted to fibers. A second lumen may be used to pass gas into the fiber producing device. Second lumen may be coupled to a portion of the fiber producing device500such that gas passes into fiber producing device500and out through gas outlets520, while being inhibited from entering the body which holds the material. First lumen, in a similar manner, may be coupled to a portion of the fiber producing device500such that material passes into the body of fiber producing device500and out through openings510, while being inhibited from entering gas outlets520. In applications that use a heated material for fiber production, gas entering the fiber producing device may be heated such that heated gas, preferably at or near the temperature of the heated material, is ejected from the fiber producing device.

FIG. 6depicts a projection view of another embodiment of a fiber producing device. Fiber producing device600includes a gear like body610, having a plurality of orifices disposed in groove615of each gear like extension. Body610may be composed of a top member612and a bottom member614. When coupled together top member612and bottom member614define groove615, which run around the circumference of the fiber producing device. Top member612and bottom member614together define a body cavity (not shown), in which the material to be formed into fibers is disposed. An opening620extends through top member612to the body cavity to allow material to be placed into body cavity. Use of a channel that couples directly to the body cavity allows introduction of the material from the top face of the body while the body is being rotated. Fiber producing device600is coupled to a drive using coupling member640. Coupling member, in some embodiments, has an open hub design. An open hub design features a central coupler642which is connected to a coupling ring644through one or more arms646, leaving a substantially empty area between the central coupler and the coupling ring. This open hub design helps improve air flow management around the fiber producing device.

Fiber producing devices may be heated by induction, as described herein. Induction produces currents in the body of the fiber producing device which heats the device. It is often desirable to control the location of the heating by steering the induced currents to the regions where heat is desired. InFIG. 6, a fiber producing device has radial slots660cut in the upper plate to push induced circumferential currents to the outer diameters of the device.

In a fiber producing system where the fibers are laid down on a substrate perpendicular to the axis of rotation, below the fiber producing device, it is important that the spread of the fibers be controlled such that the deposited fibers are as uniform as possible across the deposition width. Several system parameters influence, and can be altered, to control the spread of fibers. For example, rotational velocity, chamber air flow, and distance between the fiber producing device and the substrate are among the system parameters than may be easily modified.

An additional parameter that may be used to modify the spread of fibers is the air flow at the openings of the fiber producing device. One way to control the air flow at the openings of a fiber producing device is to alter the shape of the body. It has been found that the body of a fiber producing device can be shaped in a way such that the air flow between the top surface and the bottom surface of the body creates different velocities in the vicinity of the openings. Thus the fiber trajectory may be controlled by changing the shape of the body. Generally, the shape of the sides of the body have the most effect on the airflow around the openings. For example, varying the diameter between the top surface and the bottom surface of the body of a fiber producing device can create different air flows proximate to the openings.

FIGS. 7A-Bdepict an embodiment of a fiber producing device700. Fiber producing device700includes a substantially circular body710having an internal cavity. One or more openings730are formed in the sidewalls of the fiber producing device communicating with the internal cavity. Openings730may include two rows of openings arranged as two substantially parallel lines of openings. Both lines are spaced an equal distance from center717of body710. A coupling member720is coupled to the body. The coupling member is used to couple body710to a driver.

In one embodiment, the diameter of the body varies between a top surface712and a bottom surface714. In this embodiment, the body has a symmetrical profile. For example, body710has a rounded top portion713and a rounded bottom portion715. Thus body710has a diameter at top portion713that is less than the diameter at center717of the body and a diameter at bottom portion715that is less than the diameter at center717of the body. The reduced diameter of the top and bottom portions of body710creates a predefined airflow in a region proximate to the openings. The predefined airflow enhances the movement of the fibers away from the fiber producing device in a manner that will help ensure a mote even distribution of the fibers when deposited on a substrate. The profile of fiber producing device700is such that central portion717of body710is substantially vertical, and lies in a line parallel with the axis of rotation. The portion of body710proximate to the top portion and the bottom portion may be substantially rounded to create the varying diameter for the body. Body710further includes a plurality of vertical grooves740, formed in the sidewalls, the vertical grooves enhance the flow of air around the openings730.

FIGS. 8A-Bdepict an embodiment of a fiber producing device800. Fiber producing device800includes a substantially circular body810having an internal cavity. One or more openings830are formed in the sidewalls of the fiber producing device communicating with the internal cavity. Openings830may include two rows of openings arranged as two substantially parallel lines of openings. Both lines are spaced an equal distance from center817of body810. A coupling member820is coupled to the body. The coupling member is used to couple body810to a driver.

In one embodiment, the diameter of the body varies between a top surface812and a bottom surface814. In this embodiment, the body has a symmetrical profile. For example, body810has a rounded top portion813and a rounded bottom portion815. Thus body810has a diameter at top portion813that is less than the diameter at center817of the body and a diameter at bottom portion815that is less than the diameter at center817of the body. The reduced diameter of the top and bottom portions of body810creates a predefined airflow in a region proximate to the openings. The predefined airflow enhances the movement of the fibers away from the fiber producing device in a manner that will help ensure a mote even distribution of the fibers when deposited on a substrate. The profile of fiber producing device800, in contrast to fiber producing device800(SeeFIG. 8), is substantially rounded from center817to top surface812and from the center to the bottom surface814to create the varying diameter for the body.

FIGS. 9A-Bdepict an embodiment of a fiber producing device900. Fiber producing device900includes a substantially circular body910having an internal cavity. One or more openings930are formed in the sidewalls of the fiber producing device communicating with the internal cavity. Openings930may include a single row of openings or two rows of openings arranged as two substantially parallel lines of openings. When two lines of openings are present, both lines are spaced an equal distance from center917of body910. A coupling member920is coupled to the body. The coupling member is used to couple body910to a driver. It should be understood that two lines of openings is merely illustrative, the number of lines of openings may be two or more.

In one embodiment, the diameter of the body varies between a top surface912and a bottom surface914. In this embodiment, the body has an asymmetrical profile. Body910has a rounded top portion913and a rounded bottom portion915. Thus body910has a diameter at top portion913that is less than the diameter at center917of the body and a diameter at bottom portion915that is less than the diameter at center917of the body. The reduced diameter of the top and bottom portions of body910creates a predefined airflow in a region proximate to the openings. The predefined airflow enhances the movement of the fibers away from the fiber producing device in a manner that will help ensure a mote even distribution of the fibers when deposited on a substrate. The profile of fiber producing device900is asymmetrical. Thus the top portion is substantially rounded from an off center position925to top surface912and from the off center position925to the bottom surface914to create an asymmetrical profile. Body910further includes a plurality of vertical grooves940, formed in the sidewalls, the vertical grooves enhance the flow of air around the openings930.

Other modifications to fiber producing systems have been contemplated and are described below.FIG. 10depicts a schematic cross-section view of a fiber producing device1000. Fiber producing device1000includes a body channel1010which receives material to be produced into fibers. Body channel1010is configured to hold material in a vertical orientation. In one embodiment, body channel1010has a vertical dimension1020that is larger than the lateral dimension1030of the channel, with respect to the body. During use, material may be placed in the channel from a material transfer conduit1050. The material disposed in channel1010flows substantially vertically through the body, rather than laterally as described in other fiber producing devices. The material flows through channel1010into one or more openings1040passing through a sidewall of the body. In some embodiments, channel1010is substantially angled toward one or more of the openings. Use of vertical channels reduced the heated volume of the fiber producing device. This leads to lower power requirements and better temperature uniformity.

In another embodiment, sensors embedded in a fiber producing device, or coupled to the surface of a fiber producing device, may be used to monitor the temperature of a fiber producing device.FIG. 11depicts a schematic diagram of a fiber producing device1100having one or more sensors1110. Sensors may be powered and transmit and receive signals by use of a rotary electric device1120coupled to connecting member1130of fiber producing device1100. In one embodiment, rotary electric device1120is a rotary transformer. A rotary transformer is a transformer used to couple electrical signals between two parts that rotate in relation to each other. In an embodiment, a rotary transformer includes a primary winding1024and a secondary winding1028with each winding facing each other. Primary winding is mounted to a driver, while secondary winding is mounted to the connecting member. Suring use connecting member (and thus secondary winding) rotates with respect to the driver. Magnetic flux provides an electrical coupling from the primary winding to the secondary winding across an air gap, providing the mutual inductance that couples energy across the rotary transformer. The coupled energy is provided to the heating devices to create heat in the fiber producing body. In other embodiments, rotary electric device1120is a set of electrical brushes or slip rings.

Sensors1110may be disposed partially or entirely within a body1115of fiber producing device1100. Alternatively, sensors1110may be positioned on an outer surface of the fiber producing device1110.

In an embodiment, one or more sensors1110are temperature sensors. Temperature sensors may be used to control the temperature of the fiber producing device. In one embodiment, the temperature of a fiber producing device may be measured using temperature sensors (e.g., resistive temperature sensors, infrared temperature sensors or thermocouple temperature sensors) embedded in or disposed on a fiber producing device. The temperature sensors may be coupled to the measurement electronics through rotary electric device1120. A reference temperature sensor may be incorporated on the sensor side to compensate for transformer changes.

Alternatively, temperature sensors may also be coupled to the measurement electronics through electrical brushes and slip rings. A reference temperature sensor may be incorporated on the sensor side to compensate for transformer changes or changes to the resistance of the slip ring contacts.

A controller may be used to maintain an operating temperature of the fiber producing device. For example, a controller may be coupled to one or more heating devices (disposed proximate to, on, or within the fiber producing device) and one or more temperature sensors (disposed proximate to, on or within the fiber producing device). During use, one or more temperature sensors may provide the controller with information regarding the temperature of the fiber producing device. The controller may access the temperature of the fiber producing device and operate the heating devices, as needed, to maintain the proper operating temperature of the fiber producing device. Use of a feedback temperature loop will help to minimize temperature variations in the fiber producing device that would affect fiber formation.

In an embodiment of a fiber producing system, a heating device may be positioned substantially inside a body of a fiber producing device. An embodiment of a fiber producing system is depicted inFIGS. 12A-D. Fiber producing system1200includes a fiber producing device1210. Fiber producing device1210includes a body1212and a coupling member1214. Body1212comprises one or more openings1216through which material disposed in the body may pass through during use. As discussed previously, interior cavity of the body may include angled or rounded walls to help direct material disposed in body1212toward openings1216. In some embodiments, an interior cavity of body1212may have few or no angled or rounded walls to help direct material disposed in body1212because such angled walls are not necessary due to the material and/or the speed at which the body is spinning during the process. Coupling member1214may be an elongated member extending from the body which may be coupled to a driver1218. Alternatively, coupling member may be a receiver which will accept an elongated member from a driver (e.g., the coupling member may be a chuck or a universal threaded joint).

In some embodiment, fiber producing device1210may include internal heating device1220(e.g., depicted inFIGS. 12B-C). Heating device1220may function to heat material conveyed into body1212facilitating the production of fibers as the material is conveyed through one or more openings1216. Heating device1220may heat material inductively or radiantly. In some embodiments, a heating device may heat material conductively, inductively or radiantly. In some embodiments, a heating device may heat material using RF, lasers, or infrared.

In some embodiments, heating device1220may move during use. Heating device1220may move in coordination with body1212during use. Heating device1220may be coupled to coupling member1214.

In some embodiments, heating device1220may remain substantially motionless in relation to body1212during use such that as body1212spins, heating device1220remains relatively motionless. In some embodiments, heating device1220may be coupled to elongated conduit1222. Elongated conduit1222may be at least partially positioned in coupling member1224. Elongated conduit1222may move independently of coupling member1224such that as the coupling member rotates body1212rotates without moving elongated conduit1222. In some embodiments, elongated conduit1222may supply power to heating device1220.

In some embodiments, materials used to form fibers may conveyed into a body of a fiber producing device. In some embodiments, the material may be conveyed to the body under pressure. Pressurized feed of materials into a fiber producing device may facilitate fiber production by forcing the materials through the openings in addition to the force provided by the spinning body of the device. A pressurized feed system may allow for produced fibers to be ejected from the openings at a higher velocity. A pressurized feed system may also allow for cleaning the fiber producing device by conveying gasses and/or solvents under pressure through the device to facilitate cleaning. In some embodiments, elongated conduit1222may function to convey materials to body1212. Elongated conduit1222may in some embodiments convey materials through driver1218(e.g., as depicted inFIG. 12B). Conveying materials through the elongated conduit may allow for the material to be delivered in an atmosphere other than air/oxygen. Materials may be conveyed using an inert atmosphere such as argon or nitrogen.

In some embodiments, a driver may include a direct drive coupled to a body of a fiber producing device. A direct drive system may increase the efficiency of the fiber producing system. Direct drive mechanisms are typically devices that take the power coming from a motor without any reductions (e.g., a gearbox). In addition to increased efficiency a direct drive has other advantages including reduced noise, longer lifetime, and providing high torque a low rpm. Elongated conduit1222may in some embodiments convey materials through driver1218(e.g., as depicted inFIG. 12B), in some embodiments driver1218may include a direct driver.

FIG. 12Ddepicts an embodiment of a cross section of a body1212of a portion of a sidewall1224, top member1226, and bottom member1228of a fiber producing system. Fiber producing system1200includes a fiber producing device1210. Fiber producing device1210includes a body1212and a coupling member1214. Body1212comprises one or more openings1216through which material disposed in the body may pass through during use. Sidewall1224may include a plurality of openings1216. In some embodiments, the plurality of openings may include a patterned array of openings. The patterned array may include a repeating pattern. The pattern may be such that no opening in the pattern is aligned vertically with another opening. The pattern may be such as to include a minimum distance between openings horizontally. In some embodiments, a pattern may inhibit entwining of fibers. Inhibition of fiber entwining or “roping” may result in a more consistent fiber product and better product.

Different patterns of openings may be desired and/or one or more openings may become clogged during normal use. In some embodiments, sidewall1224of body1212may be replaced without having to replace any other components of a fiber producing device. Sidewall1224may be couplable to top member1226, and bottom member1228of a fiber producing system. Edges1230aand1230bof a sidewall may fit within channels1232aand1232bof top member1226and bottom member1228respectively. Edges1230may function to couple sidewall1224to top member1226and bottom member1228. In some embodiments, the edges of the sidewall may form a friction fit with the channels of the top and bottom members. In some embodiments, the edges of the sidewall may have a cross section similar to a cross section of the channels of the top and bottom members such that the edges may slide into the channels in a lateral direction but inhibited from being pulled out of the channels in any other direction.

In an embodiment, a heating device used to heat a fiber producing device is a radiant heater. An infrared heater is an example of a radiant heater that may be used to heat a fiber producing device. In some embodiments, a heating device may include an infrared heating device. An infrared heating device may include a device which is tuned or tunable to a specific infrared wavelength. An infrared wavelength may be chosen based upon what type of material is being heated.

Infrared radiant heating is used extensively in industry, particularly for drying of materials or fusing of coatings (e.g., powder coating, drying of paints or printed layers). Infrared heating has advantages over other forms of heating, in that the emitted radiation (if appropriately specified) is only absorbed by the substrate (or treated portions of the substrate) and not by the surrounding air or objects. Infrared heating may be defined as applying radiant energy to the part surface by direct transmission from an emitter (source). Some of the energy emitted may be reflected off the surface, some may be absorbed by the substrate and some may be transmitted though the substrate. The absorption characteristics may depend on the type of material, the colour, and the surface finish. For example, a rough, black object will absorb more infrared energy than will a smooth white object which reflects more energy. The actual behavior of infrared energy depends on the wavelength, the distance between the substrate and the emitter, the mass of the part, the surface area and the color sensitivity. Generally shorter wavelength infrared radiation penetrates further into the substrate but is more sensitive to changes in the color of the substrate. Generally speaking, polymers absorb more effectively in the medium infrared range.

When radiation is applied to a polymer surface it can be reflected, transmitted, or absorbed. It is the absorbed portion that leads to temperature increase and consequently leads to melting of the polymer. The amount of radiation absorbed by a pure unfilled thermoplastic is determined by the vibrations of its atoms. For a vibration to be infrared-active, it must be associated with a change in dipole moment which can be activated by the oscillating electric field of incident infrared radiation. Certain vibrational modes have frequencies within the infrared spectrum and can therefore absorb infrared radiation of specific wavelengths. Plastic materials absorb infrared radiation at wavelengths from about 2 to about 15 μm. Wavelengths of 3.3 to 3.5 μm correspond to vibrational modes of C—H bonds; alcohol, carboxylic acid, or amide groups absorb infrared energy at wavelengths of about 2 to about 3 μm. Absorption of infrared radiation induces molecular vibrations (e.g., stretching, rocking, etc.) which increase the temperature of the organic polymer. Infrared heating device therefore may have several advantages including restricting heating energy to the desired material. In this way less energy is wasted during the heating process because it is directed towards a specific material.

In some embodiments, a heating device (e.g., an infrared heating device) may be positioned to heat materials before and/or as they enter the body of a fiber producing device. In some embodiments, an infrared heating device may be positioned at least partially in the interior of a fiber producing device. In such embodiments, an infrared heating device may heat material conveyed through a body of the fiber producing device. The infrared heating device may function to heat the material such that the material melts such that when the body spins the material passes through openings in the body to produce fibers. The infrared heating device may further heat material in the body which was previously melted prior to introduction into the body. The infrared heating device may further heat material in the body which was previously melted prior to introduction into the body. Further heating material may function to decrease the viscosity of the material. Further heating material may function to decrease the viscosity of the material such that flowing of the material through the openings is facilitated.

In some embodiments, an infrared heating system may be used to heat at least a portion of the environment substantially adjacent to a body of the fiber producing device. Specifically the infrared heating system may be used to heat at least a portion of the environment substantially adjacent to a plurality of openings in the body through which the material is conveyed in order to produce the fibers. Heating the environment around the body of the fiber producing device may allow for longer fibers to be produced by extending the quench rate of fibers exiting the openings in the body of the fiber producing device. By adjusting the infrared heating device one may adjust a length of the fibers produced by the fiber producing device.

An embodiment of a fiber producing device comprising a band coupled to a body is depicted inFIG. 13. Fiber producing device1300, includes a body1310, a band1320, and a coupling member1330. Band1320includes one or more openings1325passing through the sidewalls of the band. During use, rotation of the body causes material in the body cavity to be passed through one or more openings of the band and ejected from one or more openings to produce microfibers and/or nanofibers. Band1320may be formed from any suitable material including metals (e.g., stainless steel) and polymers. The material used to from the band may be selected to be compatible with the material being processed and the processing method (e.g., hot melt, or solution based applications). In some embodiments, band1320is removably coupled to body1320. Band1320may be easily removed from the body and replaced with a replacement band having the same or different configuration of openings (e.g., different size or pattern of openings). In this manner, fiber producing device1300may be customized for different applications by simply replacing band1320. In another embodiment, openings formed in band1320may be altered by placing grommets in the openings. A grommet may have a shape that allows it to be fitted within the opening to alter the size of the opening. Generally, a grommet may be used to reduce the size of one or more openings. In this manner, a single band may be customized by use of grommets to alter the size of one or more of the openings.

FIGS. 14-16depict an alternate embodiment of a fiber producing device. Fiber producing device1400includes a body1410, having a plurality of orifices disposed in slot1420. Body1410may be composed of two or more members. In the embodiment depicted a grooved member1414is placed on grooved support1418. Support1418provides a base upon which the grooved members may be stacked. Support1418also includes a coupling member1430which may be used to couple fiber producing device1400to a driver. While two grooved members are depicted, it should be understood that more or less grooved members may be used.

In one embodiment, fiber producing device1400includes a top member1412and a support member1418with one or more grooved members (1414,1416) sandwiched between the top member and the support member. To assemble fiber producing device1400, a first grooved member1416is placed on support1418. A seal (not shown) may be disposed between grooved member1416and support1418. A second grooved member1414is placed on first grooved member1416. A seal (not shown) may be disposed between second grooved member1414and first grooved member1416. When coupled together first grooved member1416and second grooved member1414define slot1420, which runs around the circumference of the fiber producing device. Top member1412is placed on second grooved member1414and is fastened to support member1418by fasteners1440, which extend through the top member, first, and second groove members into the support member. A seal (not shown) may be disposed between top member1412and second grooved member1414. When coupled together top member1412and second grooved member1414define a slot1420, which runs around the circumference of the fiber producing device.

When fiber producing device1400is assembled, a body cavity1430is defined by support member1418, grooved members1416and1414, and top member1412. Material may be placed into body cavity1460during use. A plurality of grooves1450are formed in grooved members1414and1416. When fiber producing device1400is rotated, material disposed in body cavity1460enters grooves1450, which transports the material through the fiber producing device to be ejected through openings at slot1420.

FIG. 15depicts a close up projection view of grooves1450. In an embodiment, a groove1450includes a first channel1454and a second channel1415, which is narrower than the first channel. In an embodiment, when the fiber producing device is assembled, first channel1454forms a capillary tube that extends through the side wall of the fiber producing device. The material flows through the first channel capillary tube into the second channel1415, which acts as a trough extending from the first channel. In some embodiments, second channel1415is a semi-circular channel that is not sealed by another portion of stacked fiber producing device1400. Referring back toFIG. 14, slot1420represents a region of fiber producing device1400in which second channels1415reside. Having a wider, open, second channel1415positioned next to a capillary like first channel1454removes the hold-back forces (e.g., non-slip condition at a wall) from a portion of the material as it exits the opening. Furthermore, the wide, open, second channel1415causes the material to accelerate while still in contact with the hot metal of the fiber producing device. This allows the material (especially a hot melt stream) to thin out as it accelerates, giving a smaller effective nozzle diameter, when the material leaves the fiber producing device.

In some embodiments, a hydrophobic coating may be formed on the surface of an internal cavity of a fiber producing device. The hydrophobic coating may inhibit the deposition of hydrophilic material on the surface of the internal cavity. Likewise, a hydrophilic coating may be used to protect the surface of an internal cavity of a fiber producing device that is being used to form hydrophobic fibers.

Fibers represent a class of materials that are continuous filaments or that are in discrete elongated pieces, similar to lengths of thread. Fibers are of great importance in the biology of both plants and animals, e.g., for holding tissues together. Human uses for fibers are diverse. For example, fibers may be spun into filaments, thread, string, or rope. Fibers may also be used as a component of composite materials. Fibers may also be matted into sheets to make products such as paper or felt. Fibers are often used in the manufacture of other materials.

Fibers as discussed herein may be created using, for example, a solution spinning method or a melt spinning method. In both the melt and solution spinning methods, a material may be put into a fiber producing device which is spun at various speeds until fibers of appropriate dimensions are made. The material may be formed, for example, by melting a solute or may be a solution formed by dissolving a mixture of a solute and a solvent. Any solution or melt familiar to those of ordinary skill in the art may be employed. For solution spinning, a material may be designed to achieve a desired viscosity, or a surfactant may be added to improve flow, or a plasticizer may be added to soften a rigid fiber. In melt spinning, solid particles may comprise, for example, a metal or a polymer, wherein polymer additives may be combined with the latter. Certain materials may be added for alloying purposes (e.g., metals) or adding value (such as antioxidant or colorant properties) to the desired fibers.

Non-limiting examples of reagents that may be melted, or dissolved or combined with a solvent to form a material for melt or solution spinning methods include polyolefin, polyacetal, polyamide, polyester, cellulose ether and ester (e.g., cellulose acetate, cellulose diacetate, cellulose triacetate, etc.), polyalkylene sulfide, polyarylene oxide, polysulfone, modified polysulfone polymers and mixtures thereof. Non-limiting examples of solvents that may be used include oils, lipids and organic solvents such as DMSO, toluene and alcohols. Water, such as de-ionized water, may also be used as a solvent. For safety purposes, non-flammable solvents are preferred.

In either the solution or melt spinning method, as the material is ejected from the spinning fiber producing device, thin jets of the material are simultaneously stretched and dried or stretched and cooled in the surrounding environment. Interactions between the material and the environment at a high strain rate (due to stretching) leads to solidification of the material into fibers, which may be accompanied by evaporation of solvent. By manipulating the temperature and strain rate, the viscosity of the material may be controlled to manipulate the size and morphology of the fibers that are created. A wide variety of fibers may be created using the present methods, including novel fibers such as polypropylene (PP) nanofibers. Non-limiting examples of fibers made using the melt spinning method include polypropylene, acrylonitrile butadiene styrene (ABS) and nylon. Non-limiting examples of fibers made using the solution spinning method include polyethylene oxide (PEO) and beta-lactams.

The creation of fibers may be done in batch modes or in continuous modes. In the latter case, material can fed continuously into the fiber producing device and the process can be continued over days (e.g., 1-7 days) and even weeks (e.g., 1-4 weeks).

The methods discussed herein may be used to create, for example, nanocomposites and functionally graded materials that can be used for fields as diverse as, for example, drug delivery and ultrafiltration (such as electrets). Metallic and ceramic nanofibers, for example, may be manufactured by controlling various parameters, such as material selection and temperature. At a minimum, the methods and apparatuses discussed herein may find application in any industry that utilizes micro- to nano-sized fibers and/or micro- to nano-sized composites. Such industries include, but are not limited to, material engineering, mechanical engineering, military/defense industries, biotechnology, medical devices, tissue engineering industries, food engineering, drug delivery, electrical industries, or in ultrafiltration and/or micro-electric mechanical systems (MEMS).

Some embodiments of a fiber producing device may be used for melt and/or solution processes. Some embodiments of a fiber producing device may be used for making organic and/or inorganic fibers. With appropriate manipulation of the environment and process, it is possible to form fibers of various configurations, such as continuous, discontinuous, mat, random fibers, unidirectional fibers, woven and nonwoven, as well as fiber shapes, such as circular, elliptical and rectangular (e.g., ribbon). Other shapes are also possible. The produced fibers may be single lumen or multi-lumen.

By controlling the process parameters, fibers can be made in micron, sub-micron and nano-sizes, and combinations thereof. In general, the fibers created will have a relatively narrow distribution of fiber diameters. Some variation in diameter and cross-sectional configuration may occur along the length of individual fibers and between fibers.

Generally speaking, a fiber producing device helps control various properties of the fibers, such as the cross-sectional shape and diameter size of the fibers. More particularly, the speed and temperature of a fiber producing device, as well as the cross-sectional shape, diameter size and angle of the outlets in a fiber producing device, all may help control the cross-sectional shape and diameter size of the fibers. Lengths of fibers produced may also be influenced by the choice of fiber producing device used.

The temperature of the fiber producing device may influence fiber properties, in certain embodiments. Both resistance and inductance heaters may be used as heat sources to heat a fiber producing device. In certain embodiments, the fiber producing device is thermally coupled to a heat source that may be used to adjust the temperature of the fiber producing device before spinning, during spinning, or both before spinning and during spinning. In some embodiments, the fiber producing device is cooled. For example, a fiber producing device may be thermally coupled to a cooling source that can be used to adjust the temperature of the fiber producing device before spinning, during spinning, or before and during spinning. Temperatures of a fiber producing device may range widely. For example, a fiber producing device may be cooled to as low as −20 C or heated to as high as 2500 C. Temperatures below and above these exemplary values are also possible. In certain embodiments, the temperature of a fiber producing device before and/or during spinning is between about 4° C. and about 400° C. The temperature of a fiber producing device may be measured by using, for example, an infrared thermometer or a thermocouple.

The speed at which a fiber producing device is spun may also influence fiber properties. The speed of the fiber producing device may be fixed while the fiber producing device is spinning, or may be adjusted while the fiber producing device is spinning. Those fiber producing devices whose speed may be adjusted may, in certain embodiments, be characterized as variable speed fiber producing devices. In the methods described herein, the fiber producing device may be spun at a speed of about 500 RPM to about 25,000 RPM, or any range derivable therein. In certain embodiments, the fiber producing device is spun at a speed of no more than about 50,000 RPM, about 45,000 RPM, about 40,000 RPM, about 35,000 RPM, about 30,000 RPM, about 25,000 RPM, about 20,000 RPM, about 15,000 RPM, about 10,000 RPM, about 5,000 RPM, or about 1,000 RPM. In certain embodiments, the fiber producing device is rotated at a rate of about 5,000 RPM to about 25,000 RPM.

In an embodiment, a method of creating fibers, such as microfibers and/or nanofibers, includes: heating a material; placing the material in a heated fiber producing device; and, after placing the heated material in the heated fiber producing device, rotating the fiber producing device to eject material to create nanofibers from the material. In some embodiments, the fibers may be microfibers and/or nanofibers. A heated fiber producing device is a structure that has a temperature that is greater than ambient temperature. “Heating a material” is defined as raising the temperature of that material to a temperature above ambient temperature. “Melting a material” is defined herein as raising the temperature of the material to a temperature greater than the melting point of the material, or, for polymeric materials, raising the temperature above the glass transition temperature for the polymeric material. In alternate embodiments, the fiber producing device is not heated. Indeed, for any embodiment that employs a fiber producing device that may be heated, the fiber producing device may be used without heating. In some embodiments, the fiber producing device is heated but the material is not heated. The material becomes heated once placed in contact with the heated fiber producing device. In some embodiments, the material is heated and the fiber producing device is not heated. The fiber producing device becomes heated once it comes into contact with the heated material.

A wide range of volumes/amounts of material may be used to produce fibers. In addition, a wide range of rotation times may also be employed. For example, in certain embodiments, at least 5 milliliters (mL) of material are positioned in a fiber producing device, and the fiber producing device is rotated for at least about 10 seconds. As discussed above, the rotation may be at a rate of about 500 RPM to about 25,000 RPM, for example. The amount of material may range from mL to liters (L), or any range derivable therein. For example, in certain embodiments, at least about 50 mL to about 100 mL of the material are positioned in the fiber producing device, and the fiber producing device is rotated at a rate of about 500 RPM to about 25,000 RPM for about 300 seconds to about 2,000 seconds. In certain embodiments, at least about 5 mL to about 100 mL of the material are positioned in the fiber producing device, and the fiber producing device is rotated at a rate of 500 RPM to about 25,000 RPM for 10-500 seconds. In certain embodiments, at least 100 mL to about 1,000 mL of material is positioned in the fiber producing device, and the fiber producing device is rotated at a rate of 500 RPM to about 25,000 RPM for about 100 seconds to about 5,000 seconds. Other combinations of amounts of material, RPMs and seconds are contemplated as well.

Typical dimensions for fiber producing devices are in the range of several inches in diameter and in height. In some embodiments, a fiber producing device has a diameter of between about 1 inch to about 60 inches, from about 2 inches to about 30 inches, or from about 5 inches to about 25 inches. The height of the fiber producing device may range from about 0.5 inch to about 10 inches, from about 2 inches to about 8 inches, or from about 3 inches to about 5 inches.

In certain embodiments, fiber producing device includes at least one opening and the material is extruded through the opening to create the nanofibers. In certain embodiments, the fiber producing device includes multiple openings and the material is extruded through the multiple openings to create the nanofibers. These openings may be of a variety of shapes (e.g., circular, elliptical, rectangular, square) and of a variety of diameter sizes (e.g., 0.01-0.80 mm). When multiple openings are employed, not every opening need be identical to another opening, but in certain embodiments, every opening is of the same configuration. Some opens may include a divider that divides the material, as the material passes through the openings. The divided material may form multi-lumen fibers.

In an embodiment, material may be positioned in a reservoir of a fiber producing device. The reservoir may, for example, be defined by a concave cavity of the heated structure. In certain embodiments, the heated structure includes one or more openings in communication with the concave cavity. The fibers are extruded through the opening while the fiber producing device is rotated about a spin axis. The one or more openings have an opening axis that is not parallel with the spin axis. The fiber producing device may include a body that includes the concave cavity and a lid positioned above the body.

Another fiber producing device variable includes the material(s) used to make the fiber producing device. Fiber producing devices may be made of a variety of materials, including metals (e.g., brass, aluminum, stainless steel) and/or polymers. The choice of material depends on, for example, the temperature the material is to be heated to, or whether sterile conditions are desired.

Any method described herein may further comprise collecting at least some of the microfibers and/or nanofibers that are created. As used herein “collecting” of fibers refers to fibers coming to rest against a fiber collection device. After the fibers are collected, the fibers may be removed from a fiber collection device by a human or robot. A variety of methods and fiber (e.g., nanofiber) collection devices may be used to collect fibers.

Regarding the fibers that are collected, in certain embodiments, at least some of the fibers that are collected are continuous, discontinuous, mat, woven, nonwoven or a mixture of these configurations. In some embodiments, the fibers are not bundled into a cone shape after their creation. In some embodiments, the fibers are not bundled into a cone shape during their creation. In particular embodiments, fibers are not shaped into a particular configuration, such as a cone figuration, using gas, such as ambient air, that is blown onto the fibers as they are created and/or after they are created.

Present method may further comprise, for example, introducing a gas through an inlet in a housing, where the housing surrounds at least the heated structure. The gas may be, for example, nitrogen, helium, argon, or oxygen. A mixture of gases may be employed, in certain embodiments.

The environment in which the fibers are created may comprise a variety of conditions. For example, any fiber discussed herein may be created in a sterile environment. As used herein, the term “sterile environment” refers to an environment where greater than 99% of living germs and/or microorganisms have been removed. In certain embodiments, “sterile environment” refers to an environment substantially free of living germs and/or microorganisms. The fiber may be created, for example, in a vacuum. For example the pressure inside a fiber producing system may be less than ambient pressure. In some embodiments, the pressure inside a fiber producing system may range from about 1 millimeters (mm) of mercury (Hg) to about 700 mm Hg. In other embodiments, the pressure inside a fiber producing system may be at or about ambient pressure. In other embodiments, the pressure inside a fiber producing system may be greater than ambient pressure. For example the pressure inside a fiber producing system may range from about 800 mm Hg to about 4 atmospheres (atm) of pressure, or any range derivable therein.

In certain embodiments, the fiber is created in an environment of 0-100% humidity, or any range derivable therein. The temperature of the environment in which the fiber is created may vary widely. In certain embodiments, the temperature of the environment in which the fiber is created can be adjusted before operation (e.g., before rotating) using a heat source and/or a cooling source. Moreover, the temperature of the environment in which the fiber is created may be adjusted during operation using a heat source and/or a cooling source. The temperature of the environment may be set at sub-freezing temperatures, such as −20° C., or lower. The temperature of the environment may be as high as, for example, 2500° C.

The material employed may include one or more components. The material may be of a single phase (e.g., solid or liquid) or a mixture of phases (e.g., solid particles in a liquid). In some embodiments, the material includes a solid and the material is heated. The material may become a liquid upon heating. In another embodiment, the material may be mixed with a solvent. As used herein a “solvent” is a liquid that at least partially dissolves the material. Examples of solvents include, but are not limited to, water and organic solvents. Examples of organic solvents include, but are not limited to: hexanes, ether, ethyl acetate, acetone, dichloromethane, chloroform, toluene, xylenes, petroleum ether, dimethylsulfoxide, dimethylformamide, or mixtures thereof. Additives may also be present. Examples of additives include, but are not limited to: thinners, surfactants, plasticizers, or combinations thereof.

The material used to form the fibers may include at least one polymer. Polymers that may be used include conjugated polymers, biopolymers, water soluble polymers, and particle infused polymers. Examples of polymers that may be used include, but are not limited to polypropylenes, polyethylenes, polyolefins, polystyrenes, polyesters, fluorinated polymers (fluoropolymers), polyamides, polyaramids, acrylonitrile butadiene styrene, nylons, polycarbonates, beta-lactams, block copolymers or any combination thereof. The polymer may be a synthetic (man-made) polymer or a natural polymer. The material used to form the fibers may be a composite of different polymers or a composite of a medicinal agent combined with a polymeric carrier. Specific polymers that may be used include, but are not limited to chitosan, nylon, nylon-6, polybutylene terephthalate (PBT), polyacrylonitrile (PAN), poly(lactic acid) (PLA), poly(lactic-co-glycolic acid) (PLGA), polyglycolic acid (PGA), polyglactin, polycaprolactone (PCL), silk, collagen, poly(methyl methacrylate) (PMMA), polydioxanone, polyphenylene sulfide (PPS); polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), polyethylene oxide (PEO), acrylonitrile butadiene, styrene (ABS), and polyvinylpyrrolidone (PVP). These polymers may be processed as either a melt or as a solution in a suitable solvent.

In another embodiment, the material used to form the fibers may be a metal, ceramic, or carbon-based material. Metals employed in fiber creation include, but are not limited to, bismuth, tin, zinc, silver, gold, nickel, aluminum, or combinations thereof. The material used to form the fibers may be a ceramic such as alumina, titania, silica, zirconia, or combinations thereof. The material used to form the fibers may be a composite of different metals (e.g., an alloy such as nitonol), a metal/ceramic composite or ceramic oxides (e.g., PVP with germanium/palladium/platinum).

The fibers that are created may be, for example, one micron or longer in length. For example, created fibers may be of lengths that range from about 1 μm to about 50 cm, from about 100 μm to about 10 cm, or from about 1 mm to about 1 cm. In some embodiments, the fibers may have a narrow length distribution. For example, the length of the fibers may be between about 1 μm to about 9 μm, between about 1 mm to about 9 mm, or between about 1 cm to about 9 cm. In some embodiments, when continuous methods are performed, fibers of up to about 10 meters, up to about 5 meters, or up to about 1 meter in length may be formed.

In certain embodiments, the cross-section of the fiber may be circular, elliptical or rectangular. Other shapes are also possible. The fiber may be a single-lumen fiber or a multi-lumen fiber.

In another embodiment of a method of creating a fiber, the method includes: spinning material to create the fiber; where, as the fiber is being created, the fiber is not subjected to an externally-applied electric field or an externally-applied gas; and the fiber does not fall into a liquid after being created.

Fibers discussed herein are a class of materials that exhibit an aspect ratio of at least 100 or higher. The term “microfiber” refers to fibers that have a minimum diameter in the range of 10 microns to 700 nanometers, or from 5 microns to 800 nanometers, or from 1 micron to 700 nanometers. The term “nanofiber” refers to fibers that have a minimum diameter in the range of 500 nanometers to 1 nanometer; or from 250 nanometers to 10 nanometers, or from 100 nanometers to 20 nanometers.

While typical cross-sections of the fibers are circular or elliptic in nature, they can be formed in other shapes by controlling the shape and size of the openings in a fiber producing device (described below). Fibers may include a blending of multiple materials. Fibers may also include holes (e.g., lumen or multi-lumen) or pores. Multi-lumen fibers may be achieved by, for example, designing one or more exit openings to possess concentric openings. In certain embodiments, such openings may include split openings (that is, wherein two or more openings are adjacent to each other; or, stated another way, an opening possesses one or more dividers such that two or more smaller openings are made). Such features may be utilized to attain specific physical properties, such as thermal insulation or impact absorbance (resilience). Nanotubes may also be created using methods and apparatuses discussed herein.

Fibers may be analyzed via any means known to those of skill in the art. For example, Scanning Electron Microscopy (SEM) may be used to measure dimensions of a given fiber. For physical and material characterizations, techniques such as differential scanning calorimetry (DSC), thermal analysis (TA) and chromatography may be used.

In particular embodiments, a fiber of the present fibers is not a lyocell fiber. Lyocell fibers are described in the literature, such as in U.S. Pat. Nos. 6,221,487, 6,235,392, 6,511,930, 6,596,033 and 7,067,444, each of which is incorporated herein by reference.

In one embodiment, microfibers and nanofibers may be produced substantially simultaneously. Any fiber producing device described herein may be modified such that one or more openings has a diameter and/or shape that produces nanofibers during use, and one or more openings have a diameter and/or shape that produces microfibers during use. Thus, a fiber producing device, when rotated will eject material to produce both microfibers and nanofibers. In some embodiments, nozzles may be coupled to one or more of the openings. Different nozzles may be coupled to different openings such that the nozzles designed to create microfibers and nozzles designed to create nanofibers are coupled to the openings. In an alternate embodiment, needles may be coupled (either directly to the openings or via a needle port). Different needles may be coupled to different openings such that needles designed to create microfibers and needles designed to create nanofibers are coupled to the openings. Production of microfibers and nanofibers substantially simultaneously may allow a controlled distribution of the fiber size to be achieved, allowing substantial control of the properties of products ultimately produced from the microfiber/nanofiber mixture.

After production of fibers is completed, it is desirable to clean the fiber producing device to allow reuse of the system. Generally, it is easiest to clean a fiber producing device when the material is in a liquid state. Once the material reverts to a solid, cleaning may be difficult, especially cleaning up small diameter nozzles and or needles coupled to the fiber producing device. The difficulty, especially with melt spinning, is that cleanup may also be difficult when the device is at an elevated temperature, especially if the fiber producing device needs to be cooled prior to handling for clean up. In some embodiments, a purge system may be couplable to fiber producing device when the fiber producing device is heated. A purge system may provide an at least partial seal between the purge system and the body of a fiber producing device such that a gas may be directed into the body, through the purge system, to create a pressurized gas inside of the body. The purge system, in some embodiments, includes a sealing member couplable to the body, a pressurized gas source, and a conduit coupling the pressurized gas source to the sealing member.

Some products that may be formed using microfibers and/or nanofibers include but are not limited to: filters using charged nanofiber and/or microfiber polymers to clean fluids; catalytic filters using ceramic nanofibers (“NF”); carbon nanotube (“CNT”) infused nanofibers for energy storage; CNT infused/coated NF for electromagnetic shielding; mixed micro and NF for filters and other applications; polyester infused into cotton for denim and other textiles; metallic nanoparticles or other antimicrobial materials infused onto/coated on NF for filters; wound dressings, cell growth substrates or scaffolds; battery separators; charged polymers or other materials for solar energy; NF for use in environmental clean-up; piezoelectric fibers; sutures; chemical sensors; textiles/fabrics that are water & stain resistant, odor resistant, insulating, self-cleaning, penetration resistant, anti-microbial, porous/breathing, tear resistant, and wear resistant; force energy absorbing for personal body protection armor; construction reinforcement materials (e.g., concrete and plastics); carbon fibers; fibers used to toughen outer skins for aerospace applications; tissue engineering substrates utilizing aligned or random fibers; tissue engineering Petri dishes with aligned or random nanofibers; filters used in pharmaceutical manufacturing; filters combining microfiber and nanofiber elements for deep filter functionality; hydrophobic materials such as textiles; selectively absorbent materials such as oil booms; continuous length nanofibers (aspect ratio of more than 1,000 to 1); paints/stains; building products that enhance durability, fire resistance, color retention, porosity, flexibility, anti microbial, bug resistant, air tightness; adhesives; tapes; epoxies; glues; adsorptive materials; diaper media; mattress covers; acoustic materials; and liquid, gas, chemical, or air filters.

Fibers may be coated after formation. In one embodiment, microfibers and/or nanofibers may be coated with a polymeric or metal coating. Polymeric coatings may be formed by spray coating the produced fibers, or any other method known for forming polymeric coatings. Metal coatings may be formed using a metal deposition process (e.g., CVD).