Patent Publication Number: US-11642266-B2

Title: Patient support apparatus with magnetorheological material

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to U.S. Provisional Patent Application Ser. No. 62/892,923, filed Aug. 28, 2019, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     The present disclosure relates to patient support apparatuses, such as beds, cots, stretchers, operating tables, recliners, wheelchairs, and the like. More specifically, the present disclosure relates to a redistribution of pressure from the support structures and support substrates within the patient support apparatus, such as a patient mattress or components thereof, which ultimately provide a patient support surface. 
     When patients are hospitalized or bedridden for any significant amount of time, patients can develop pressure sores or ulcers. Pressure sores or ulcers typically form as a result of prolonged immobility, which allows the pressure exerted on the patient&#39;s skin from the mattress to decrease circulation in the patient&#39;s tissue. These pressure sores or ulcers can be exacerbated by the patient&#39;s own poor circulation, such as in the case of diabetic patients. In addition to reducing circulation in the patients&#39; tissue, lack of mobility can also cause moisture build-up at the point of contact with the mattress. Moisture build-up can cause maceration in the skin, which makes the skin more permeable and vulnerable to irritants and stresses, such as stresses caused by pressure or by shear, for example, when a patient is moved across a mattress. 
     To reduce the chance of developing pressure ulcers, it is known to try and redistribute the pressure, for example, by repositioning a patient so that the pressure is redistributed to another portion of the patient&#39;s body. However, in certain instances, repositioning may not be possible or does not adequately address the patient&#39;s medical needs. 
     While different patient support apparatuses are available in various sizes and shapes, configured to support patients of various weights and personal attributes, the support structures that ultimately provide a non-powered patient support surface can only be designed and optimized for a pressure distribution around a specific patient weight. Typically, the support structures are optimized for a median patient weight, based on population. As such, this reduces performance at far ends of the spectrum for lighter or heavier patients within that population. 
     Accordingly there is a need for a mattress that can reduce the pressure on a patient&#39;s skin that is not limited in design to a median weight patient, and further that can maintain or improve air circulation to the patient&#39;s skin, all in an attempt to improve the care of the patient. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present teachings will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG.  1    is a top-side perspective view of an exemplary patient support apparatus provided as a gatch-type hospital bed; 
         FIG.  2    is a top-side perspective view of an exemplary patient support provided as a mattress useful with the hospital bed of  FIG.  1   ; 
         FIG.  3    is a top-side perspective view of the exemplary patient support of  FIG.  2    without a protective cover according to a first aspect; 
         FIG.  4    is a cross-sectional view of the exemplary patient support taken along the line  4 - 4  of  FIG.  3   ; 
         FIG.  5    is a exploded top-side perspective view of an exemplary patient support of  FIG.  2    without a protective cover according to a second aspect; 
         FIG.  6    is a top-side perspective view of an exemplary support substrate component of the patient support of  FIGS.  2  and  5    including a plurality of transversely extending cells; 
         FIG.  7    is a magnified perspective view of a portion of the support substrate component of  FIG.  6   ; 
         FIG.  8    is a cross-sectional view of a support substrate component subjected to pressure from a weight, illustrating a controlled buckling of cell walls of the support substrate component; 
         FIG.  9    is a magnified partial cross sectional view illustrating an interior region of an exemplary support substrate component with dome top cells according to various aspects of the present technology; 
         FIG.  10    is a side perspective view of a portion of a support substrate component with hexagonal shaped cells having shaped caps according to another aspect of the present technology; 
         FIGS.  11 A- 11 C  are cross-sectional views of exemplary cells of a support substrate component provided with cells having a dome top ( FIG.  11 A ), a dome top with a hole ( FIG.  11 B ), and a buttressed dome top ( FIG.  11 C ); 
         FIG.  12    is a top-side perspective view of the exemplary patient support of  FIG.  2    with a plurality of separate zones configured to support different areas of a patient body; 
         FIG.  13    is top-side perspective view of the exemplary patient support of  FIG.  12    with a patient resting thereon; and 
         FIG.  14    is a top-side perspective view of an exemplary patient support apparatus shown with a plurality of separate zones that may be useful with the present technology. 
     
    
    
     It should be noted that the figures set forth herein are intended to exemplify the general characteristics of the systems, methods, and devices among those of the present technology, for the purpose of the description of certain aspects. These figures may not precisely reflect the characteristics of any given aspect, and are not necessarily intended to define or limit specific embodiments within the scope of this technology. Further, certain aspects may incorporate features from a combination of figures, while other aspects may incorporate only portions of features from a single figure. 
     DETAILED DESCRIPTION 
     The present technology generally provides an enhanced patient support apparatus with strategic stiffening features, as well as integral thermal management and airflow features, in order to deliver enhanced patient care and reduce the development of pressure sores, ulcers, and the like. In order to afford a more tailored stiffness of a patient support surface, the present technology uses one or more magnetorheological materials disposed in a patient support/mattress or another support component thereof, such as a foam component, a support substrate, a cushion, and the like. When an electrical current or a magnetic field is applied or energized adjacent the magnetorheological material, the magnetic particles disposed within the magnetorheological material realign and ultimately change the stiffness in the patient support, support substrate, or cushion or support component. In various aspects, the stiffness or rigidity can be manipulated by the amount and type of magnetorheological materials present, the structure of the magnetorheological materials, as well as the intensity of the electrical current or magnetic field that is applied or energized. For example, as the intensity increases, the patient support surface becomes more rigid, which affects the indentation force deflection (IFD) of at least a portion of the patient support. 
     In various aspects, as will be detailed below, correlations can be made between the applied current or magnetic field, and an optimized mattress stiffness for a given patient, thereby providing an optimal pressure redistribution that can be adjusted in real time. For example, a care giver can enter (or otherwise obtain) certain patient data, such as height, weight, age, mobility issues, tissue interface pressure (TIP) data, and/or various other medical data, and the present technology can determine an optimum buckling load of the patient support, or portion thereof, and manipulate a magnetorheological material in order to adjust a stiffness of one or more regions prior to the patient being placed on the patient support apparatus. It is also envisioned that one or more stiffness features may be monitored and changed/corrected as needed after the patient is placed onto the mattress. 
     For a more complete understanding of the present teachings, reference is made to  FIG.  1   , illustrating one example of a patient support apparatus  18  with an adjustable frame that is configured as a bed  20  and generally adapted for use in a hospital or other medical setting.  FIG.  1    is a top-side perspective view of an exemplary bed  20  with a raised head section. Although the particular form of the patient support apparatus illustrated in  FIG.  1    is a bed, it should be understood that patient support apparatuses useful with the present technology may also include, in different embodiments, stretchers; gurneys; cots; trolleys; operating tables; benches; wheelchairs, as well as traditional chairs, seats, and recliners; or any other similar type of structure capable of supporting a patient, whether stationary or mobile and/or whether used for medical or residential environments. In still other aspects, the patient support apparatus may be configured to change in shape and function, for example, between a stretcher or bed and a chair. 
     The exemplary gatch-type hospital bed  20  as shown in  FIG.  1    includes a base  22 , an automated drive system such as a pair of lifts  24 , an adjustable frame commonly referred to as a litter assembly  26 , a patient support deck  28 , a headboard  30 , and a footboard  32 . The base  22  includes a plurality of wheels  34  that can be selectively locked and unlocked so that, when unlocked, the patient support apparatus  18  is able to be wheeled to different locations. Certain of the wheels  34  may be steering type wheels, with castors or otherwise configured to rotate up to 360 degrees, other wheels may not be rotatable. The base  22  may include one or more retractable wheels (not shown) to provide controlled traction and cornering. The base  22  may also include one or more powered wheels, the movement of which can be operated by a controller. Certain wheels  34  may be provided with locking mechanisms (not specifically shown). The lifts  24  are generally configured to raise and lower the litter assembly  26  with respect to the base  22 . In this regard, the lifts  24  may include hydraulic actuators, electric actuators, or any other suitable device for raising and lowering the litter assembly  26  with respect to the base  22 . In some embodiments, the lifts  24  may operate independently so that the orientation of litter assembly  26  with respect to the base  22  may also be adjusted. The lifts  24  may be of various designs; certain lifts  24  are configured to raise and lower extending legs or columns in a substantially vertical direction, while others include hinges or scissor type lift mechanisms having linked, folding supports in a crisscross or ‘X’ pattern. 
     The litter assembly  26  of the bed  20  of  FIG.  1    provides a structure for coupling with the supporting deck  28 , a headboard  30 , and a footboard  32 . The supporting deck  28  provides a surface on which a patient support, such as mattress  36 , or other support member, is positioned defining a patient support surface  38  where a patient may lie and/or sit thereon. The deck  28  may be made of a plurality of sections, some of which are pivotable about generally horizontal pivot axes. In the embodiment shown in  FIG.  1   , the deck  28  includes a head section  40 , a foot section  42 , and one or more intermediate sections  44 . The head section  40 , which is also sometimes referred to as a fowler section, is pivotable with respect to the intermediate section  44  between a generally horizontal orientation and a plurality of raised positions (one of which is shown in  FIG.  1   ). The foot section  42 , which is also sometimes referred to as a gatch section, is also pivotable with respect to the intermediate section  44  between a generally horizontal orientation (shown in  FIG.  1   ) and a plurality of lowered positions (not shown). In certain aspects, the head section  40  may be lowered, and the foot section  42  may be raised or elevated, with respect to the intermediate section  44 , for example to increase blood flow to the upper body. The base  22 , the lifts  24 , the litter assembly  26 , the support deck  28  and its various sections  40 ,  42 ,  44 , as well as other movable components, may each be provided with the necessary mechanical structures, actuators, automated drive mechanisms, etc. for exhibiting independent and automated movement, control, and related capabilities of the patient support apparatuses  18 . 
     The various patient support apparatuses  18  may also include a plurality of side rails, collectively referred to by reference number  46 . For example, the bed of  FIG.  1    includes a right head side rail  46   a , a right foot side rail  46   b , a left head side rail  46   c , and a left foot side rail  46   d . The side rails  46  are generally movable between a raised position and a lowered position, and in various aspects can be locked or provided at intermediate positions. The side rails  46  can be provided with handle areas for use by the patient or caregiver. In the configuration shown in  FIG.  1   , all four of the side rails  46  are raised. As shown in  FIG.  1   , the interior side of the head side rails  46   a ,  46   c  may be provided with a patient control interface  48  configured to operate movement of the head section  40  and foot section  42 , as well as control other auxiliary features, such as lights, televisions, sound control, and the like. The exterior side of the head side rails  46   a ,  46   c  may be provided with a caregiver control interface  50 , similarly configured to operate movement of the bed  20 , as well as other functions. 
     As shown in  FIG.  1   , the footboard  32  may also be provided with one or more caregiver control interface  50  and/or display  52  with optional touchscreen capabilities. In certain aspects, the footboard  32  may include a controller  54  that includes the caregiver control interface  50  and display  52 . The controller  54  may include at least one processor with memory and software programmable to control various aspects of the bed  20 . The teachings of the present technology may be used with known control systems and may generally include a computing device or controller  54 , such as a control module with a processor, a memory, and an interface  50 . It should be understood that although particular systems or subsystems may be separately defined herein, each or any of the systems may be otherwise modified, combined, or segregated via appropriate hardware and/or software as is known to those of ordinary skill in the art. For example, the controller  54  may be a portion of another control device, a stand-alone unit, or other system, including cloud based. Alternatively, the controller  54  can be composed of multiple computing devices. The processor(s) may be any type of conventional microprocessor having desired performance characteristics and capable of manipulating or processing data and other information. The memory may include any type of computer readable medium that stores data and control algorithms described in more detail below. Other operational software for the processor may also be stored in the memory. The interface may facilitate communication with other systems, sensors, and other on-board systems. On-board systems and sensors may include, but are not limited to, weight sensors, diagnostic sensors, auxiliary systems and accessories, automated controls, and the like. The controller  54  can also include secondary, additional, or external storage, for example, a memory card, flash drive, or any other form of computer readable medium. Installed applications can be stored in whole or in part in the external storage and loaded into the memory as needed for processing. 
     In various aspects, the controller  54  may be located out of view, for example, secured in the base  22  or coupled to the litter assembly  26 , as appropriate. The controller  54  may alternatively be an external unit that is wired to the bed  20  or communicates via wireless communication. Thus, the bed  20  may also be provided with one or more communication module configured to establish a wireless communication. Various wireless communication protocols may be used, including Bluetooth, near-field communication (NFC), infrared communication, radio wave communication, cellular network communication, and wireless local area network communication (Wi-Fi). In certain aspects, the communication module may be a part of the controller  54 . The wireless communication may provide compatibility with information management systems. Not only can the patient support apparatuses  18  be coupled to the controller  54  using wireless communication protocols, one or more patient support apparatuses  18  can establish a communication link directly or indirectly with one another in order to share data, information, and exhibit control. 
       FIG.  2    is a top-side perspective view of an exemplary patient support  36 , such as a mattress, which ultimately defines a patient support surface  38 . As specifically shown, the patient support  36  can be described as having two main portions, a substantially horizontal portion  56  for receiving an upper body region of the patient, and an optional sloped heel portion  58  for receiving the lower leg and foot region of the of the patient, and to minimize heel breakdown. In other aspects, the two portions  56 ,  58  may both be provided as substantially horizontal across a length and width of the patient support  36 . The patient support can include a removable, protective cover  60  extending between opposing head and foot ends  62 ,  64  and across the width of the patient support  36 . In various aspects, the upper portion of the cover  60  that ultimately forms the contact surface of the patient support surface  38  may include at least a portion that is a breathable mesh material, configured to selectively allow a controlled airflow from within an interior of the patient support  36  and up between the patient support surface  38  and a patient&#39;s skin. The protective cover may also be a woven material, a flexible fabric, a plastic, or other suitable material that may be easily cleaned and sterilized and for preventing exposure of the remaining interior of the patient support  36  to an external environment. 
       FIG.  3    is a top-side perspective view of the exemplary patient support  36  of  FIG.  2    shown without a protective cover according to a first aspect.  FIG.  4    is a cross-sectional view of the exemplary patient support  36  taken along the line  4 - 4  of  FIG.  3   . As illustrated, the patient support  36  may include a number of different support components and support substrates. 
     For example, the patient support  36  may include various layers with different cushioning components and support substrate components that, in combination, assist with managing pressure redistribution while achieving optimal comfort for the patient. An uppermost layer may include an upper section of a support substrate  66  surrounded on three sides by a U-shaped section of foam, which may include opposing foam side bolsters  68  and a front or head bolster  70 . The upper support substrate  66  generally extends from the head bolster  70  to the foot end  64  of the patient support  36 . The foam side bolsters  68  flank the upper support substrate  66  and provide stability to the upper support substrate  66 . In various aspects, the foam side bolsters  68  are attached to the upper support substrate  66 . They further provide a firm edge for the support substrate  66  to ease ingress and egress for a patient. In addition, because of the firmness difference between the upper support substrate  66  and the foam bolsters  68 ,  70 , the upper support substrate  66  may tend to compress more than the foam bolsters  68 ,  70 , so that the foam bolsters  68 ,  70  form a barrier to cradle the patient in the support, which reduces the chances of a patient falling off the bed  20  on which the patient support  36  is ultimately supported. Optionally, the foam bolsters  68 ,  70  may be taller than the upper support substrate  66  to form an even taller barrier. The upper support substrate  66  may also include flanges (not shown) that extend along its length and/or width, which are formed from a fabric and are adhered to the foam side bolsters  68  and sandwiched there between to anchor the upper support substrate. 
     With reference to  FIG.  4   , the patient support  36  may include a middle layer that includes a center support substrate  72  disposed between a head area cushion  74  and a leg area cushion  76 . The center support substrate  72  is located to further assist and redistribute pressure in the sacral region and reduce return force. For example, the center support substrate  72  can isolate pressure in the sacral region by selectively buckling and absorbing the patient&#39;s weight, allowing immersion and envelopment to take place, resulting in optimal comfort. Additional cushions may also be provided, for example, in the central or torso area  78  and the thigh area  80  that have a greater density, as well as provide a higher indentation force deflection than adjacent foam or cushions. A lower foam or cushion base layer  82  may be provided adjacent the middle layer. 
     In various aspects, an air distribution bladder may optionally be included (not specifically shown) located on top of, adjacent to, and/or anchored to a base layer  82  or similar component. For example, one or both ends of the air distribution bladder may be anchored, such as by welding or by an adhesive, to the base layer  82 . In other aspects, an air distribution bladder may be located between the support substrate components  66 ,  72 . The air distribution bladder may be filled with air using an external air supply  84  (see,  FIG.  14   ) or an air supply built into the patient support  36 . For example, the air distribution bladder may include one or more inlets that couple to tubing that extends from the bladder to beneath foam base layer to connect to an air flow device, such as pump or a fan, which is then regulated by a conventional control. The pump and any supporting control system may be mounted in the support itself, such as described in U.S. Pat. Nos. 5,325,551, and 5,542,136, both commonly owned by Stryker Corporation of Kalamazoo, Mich., or may be located external to the support, for example at the footboard or the side rail, or at other locations on or off the bed. Air may be pushed or pulled through the bladder. Further, the air flow may be bidirectional. As is understood, pulling air meets with less resistance than pushing air, so pulling air may be preferred in order to reduce the size of the air flow device. The air may be cooled air, ambient air, or warmed air. In one example, a Peltier device, which can provide cold or warm air, may be incorporated into the air supply system to allow the air to be cooled or warmed as desired. 
       FIG.  5    is a top-side perspective exploded view of an exemplary patient support  36  of  FIG.  2    (without a protective cover) according to a second aspect. Similar to the patient support  36  of  FIG.  2   , the patient support  36  configuration of  FIG.  5    also provides a patient support surface  38  designed to redistribute pressure in the vulnerable sacral region, to help prevent pressure sores or ulcers, and provide optimal comfort for a superior patient experience. As shown, the patient support  36  includes an upper layer  86 , and a lower layer  88 . The upper layer  86  may extend substantially across the entirety of the patient support  36 . The lower layer  88  may include opposing side bolsters  68 , as well as an upper body cushion  90  and lower body cushion  92 . A center support substrate  72  may be specifically located to assist and redistribute pressure in the sacral region and reduce return force, similar to the aspect shown in  FIG.  2   . The combination of cushions and support substrates shown in  FIG.  5    may be designed and shaped to create a positioning pocket that helps prevent the patient from migrating to the foot end of the bed when the head of the bed is elevated. A center base layer  94  may be provided defining an aperture  96  to allow airflow between the external environment, through the center support substrate  72 , and ultimately to the patient support surface  38 . This type of airflow can be accomplished without the use of an external air circulation pump, and without any valves or air bladders, minimizing the use of additional mechanical components. 
       FIG.  6    is a top-side perspective view of an exemplary center support substrate  72  component of the patient support  36  of  FIGS.  2  and  5   .  FIG.  7    is a magnified perspective view of a corner portion of the center support substrate  72  component of  FIG.  6   . Although labeled as the center support substrate  72 , the discussion of  FIGS.  6  and  7    is equally applicable to the upper support substrate  66  of  FIGS.  3 - 4   . Still further, it should be understood that while only center and upper support substrates  66 ,  72  are shown in the figures, the patient support  36  may include various additional or alternative support substrates located therein. As will be described in more detail below, the upper and center support substrates  66 ,  72  may be formed as a lattice structure with a plurality of polygonal cells  98  with transverse openings that may be in fluid communication with the other respective layers of the patient support  36  to permit air flow to the interface between the patient and the patient support  36 , for example, at or near the patient support surface  38  of the upper support substrate  66 . The outer edges of the support substrates  66 ,  72  may include linear or shaped side walls  100 , depending on the shape of the polygonal cells  98 . For example, as shown in  FIGS.  3 - 7    and  FIGS.  12 - 13   , the polygonal cells  98  are shown as square shaped cells with four walls disposed with an interior angle of about 90 degrees with respect to one another. As shown in  FIGS.  8 - 11   , the polygonal cells  98  are shown as hexagonal shaped cells  98  with six walls disposed with an interior angle of about 120 degrees with respect to one another. 
     The present technology provides that one or more components of a patient support apparatus  18  include a magnetorheological material that can be configured to provide a selective reinforcement support of at least a portion of a patient support  36  and/or patient support surface  38  in order to redistribute pressure about a surface of a patient. In various aspects, each of the internal components of the patient support  36 , such as cushions, foam pieces, and the support substrates may play a role to ultimately define or influence, in part or in whole, an overall stiffness of the patient support  36 , including at the patient support surface  38 . As such, it is envisioned that any one or all of the various components of the patient support  36  may include a magnetorheological material. For purposes of simplicity only, the following discussion will focus on the inclusion of magnetorheological materials present in the upper and center support substrates  66 ,  72 . It should be understood, however, that the magnetorheological materials may additionally or alternatively be present in any number of the components of the patient support  36 . 
     In broad terms, non-limiting, shape conforming magnetorheological materials, as described in more detail below, may include magnetorheological fluids, magnetorheological elastomers, and magnetorheological foams. The magnetorheological material may include a distribution of ferromagnetic particles disposed therein that, upon being subjected to a magnetic field, rapidly alter their rheological properties. The movement of micron-sized ferrous particles dispersed in the magnetorheological materials and may exhibit a sharp variation in the stiffness of the magnetorheological material, capable of conforming it to a shape or adding increased rigidity to control its compression. In various aspects, the magnetic field can be introduced using an electric current or a suitable magnet, such as an electromagnet. 
     Magnetic fields are flux forces that generally arise due to the movement of an electrical charge. The movement of electrical charge may occur via the movement of electrons in an electric current, known as electromagnetism, or via the quantum-mechanical spin and orbital motion of electrons in an atom. For example, a wire that has an electrical current running through it creates a magnetic field. Thus, in various aspects of the present technology, the support substrate  66 ,  72  may be provided with electrically conductive wires and/or a circuit disposed throughout at least one region. An electrically conductive circuit may be configured to selectively generate the magnetic field which, in turn, increases the stiffness of localized areas or an entirety of the support substrate  66 ,  72 . In still other aspects, one or more magnets can be provided to create the magnetic field. In various aspects, the magnet may be an electromagnet, a permanent magnet, or a combination of both. 
     Where the magnetorheological medium is a fluid, it may be configured to selectively change state between a relatively low viscous state and a more rigid, or relatively high viscous state leading to an increased rigidity. Where the magnetorheological medium is a deformable solid, such as an elastomer or resin, it may be configured to selectively change state between a generally soft and elastic polymer or flexible film, and a more rigid, relatively stiff matrix. 
     A magnetorheological fluid (MRF) is generally a carrier fluid, such as an oil, that includes ferromagnetic particles randomly distributed therein in a functional suspension under normal circumstances. In one example, the ferromagnetic particles may be present as having a three dimensional shape, such as a sphere, ellipsoid, or the like. The ferromagnetic particles may have symmetrical as well as non-symmetrical or irregular shapes, and may also be present as rod-shaped or elongated particles. In aspects where the support substrate  66 ,  72  contains an MRF, it has the capability of changing one or more of its material properties, preferably viscosity (or the apparent viscosity), through the use of an external stimulant, preferably a magnetic field. For example, when a magnetic field is generated or otherwise applied, the ferromagnetic particles align themselves along the lines of the magnetic field, or magnetic flux. 
     Exemplary ferromagnetic particles include alloys of iron, nickel, and cobalt. Ceramics, such as sintered compositions of iron oxide and barium/strontium carbonate, as well as rare earth magnets, such as neodymium and samarium-cobalt, may also be useful with the present technology. The maximum possible magnetic field induced change in stress/modulus generally occurs when the aligned particles become magnetically saturated. While iron has been shown to have the highest saturation magnetization of elements, certain iron and cobalt alloys have even higher saturation magnetizations. Iron and cobalt alloys may also be preferred in certain aspects due to their high permeability and relatively low hysteresis loss. 
     Generally, the ferromagnetic particles may be randomly distributed within the support substrate  66 ,  72  when no magnetic field is applied. In the presence of a magnetic field of sufficient strength, however, the particles quickly acquire a magnetic polarization and will form chains of various strength, based in part on the strength of the magnetic field. It should also be understood that many of the specific features of the ferromagnetic particles such as their size/shape, distribution in the matrix, and percentage volume of the magnetic particles in the fluid or elastomer matrix can affect the overall behavior of the support substrate  66 ,  72 . 
     In various aspects when using an MRF, it may be desired to control a buoyancy or relative density of the ferromagnetic particles to minimize particle settling and agglomeration. Thus, the ferromagnetic particles may be provided having different average sizes, weights, and content in order to provide a distribution of ferromagnetic particles with a range of densities to enhance dispersion. For example, certain of the ferromagnetic particles may be provided as solid particles, and other particles may be provided having a shell with a core. The core may be hollow or may be filled with a gas or other material in an effort to adjust density and buoyancy. Particles with different core sizes may be provided as appropriate for variations in density. Certain of the ferromagnetic particles may also be provided with an outer coating, for example, an outermost polymer coating such as silicone or the like. Preferably, a thickness of the polymer coating can be selected providing a sufficient buoyancy control to minimize settling of the particles, yet providing the same functionality to form a rigid shape support substrate  66 ,  72  upon being subjected to the magnetic field. In various aspects, the polymer coating itself may also be magnetically conductive. In still other aspects, the rate and degree to which settling and agglomeration occurs may be offset to a degree with the use of a surfactant additive. However, it should be understood that the addition of a surfactant may negatively affect the magnetic saturation of the fluid, which, in turn, may affect the maximum yield stress exhibited in the activated state, which is, in turn, related to the change in apparent viscosity of the support substrate  66 ,  72 . 
     According to another alternative exemplary aspect of the present teachings, the support substrate  66 ,  72  can include one or more layer, or sheet. When present as a layer or sheet and provided as a solid or having a flexible matrix, the magnetorheological material may be present as a magnetorheological elastomer (MRE, otherwise known as a magnetosensitive elastomer), and/or include a magnetorheological foam (MR-foam). In certain instances, MREs with a porous matrix may also be referred to as foams or having a foamed matrix. Distinguished from an MRF, the presence of the layer of magnetorheological material as having a solid matrix base or a flexible matrix base (as an MRE or MR-foam) may minimize or otherwise avoid potential problems, such as particle settling of the ferromagnetic particles, as discussed above. It should be understood that an MRE can be provided in multiple layers. The layers may be adjacent one another, or separated as having an inner layer, an outer layer, and the like. Still further, an MRE may be provided in strips that may be aligned with one another or spaced apart having various designs and strengths. In this regard, it is envisioned that the strips and/or layers may be provided having different materials (elastomers and/or ferromagnetic particles), leading to different rigidity and the ability to customize the stiffness features. An MRE may also be presented with a weaved or shaped pattern or having various lattice structures. 
     MREs may include a class of elastomers that contain a polymeric matrix with embedded nano- to micro-sized ferromagnetic particles, such as carbonyl iron, arranged in a particular pattern. Common MREs may generally include a natural or synthetic rubber matrix that is then interspersed with the ferromagnetic particles. MR-foams generally provide an absorptive metal foam matrix in which a controllable fluid having the ferromagnetic particles is contained. Non-limiting exemplary metal foams may include aluminum, copper, and nickel. 
     Various different MREs can be prepared using a curing process. In one aspect, a liquid base polymer, such as silicone rubber, can be mixed with an iron powder, as well as other desired additives, and cured at a high temperature in the presence of a magnetic field. The presence of the magnetic field during the curing process is what causes a chain-like structural arrangement of the iron particles, which then results in an anisotropic material. Alternatively, it is envisioned that 3D printing techniques may also be used to configure the magnetic particles into a polymer matrix and shaped as a suitable support substrate  66 ,  72 . The composite microstructure of an exemplary MRE is such that the mechanical properties of the material can thereafter be accurately controlled with the application of a magnetic field. In other words, if a magnetic field is not applied during the curing process, the resulting material will generally be considered an elastomer ferromagnet composite (EFC) that would essentially have little or no influence on the shape or stiffness. This is because the solid elastomer matrix of the EFC would prevent the ferromagnetic particles from forming chains, which is required for the change in apparent viscosity as described below. 
     Whether present as an MRF, MRE, MR-foam, or equivalent, upon selective activation of the support substrate  66 ,  72  using a controlled stimulus, i.e., the generation of one or more magnetic field(s), the ferromagnetic particles disposed therein are nearly instantaneously (within milliseconds in most occurrences) aligned into chains and/or particle clusters that are substantially parallel to the magnetic flux/field lines. Depending on the ferromagnetic materials and strength of the magnetic field that is generated, such chains may interconnect and form fibrils that may be branched from the chains. Clusters of these chains/fibrils exhibit a very high strength and, thus, increase the rigidity of the support substrate  66 ,  72 , in certain aspects up to a maximum point such that the patient support  36  (or at least one region thereof) is functionally immobile, and will require a large amount of force in order to bend or flex. Subsequent deactivation, or removal of the magnetic field, will no longer maintain the clusters of chains/fibrils in an aligned orientation, allowing the support substrate  66 ,  72  to bend and flex again. It is envisioned that the activation and deactivation of the magnetic field can be repeated and performed any number of times, which permits ease of realignment and reuse of the patient support  36  with multiple patients of different size, shape, and with different medical needs. 
     In one non-limiting aspect of the present technology, the support substrates  66 ,  72 , can include a distribution of ferromagnetic particles disposed in a flexible polymeric material. In various examples, polymeric materials useful as forming one of the support substrates  66 ,  72  may include low durometer thermoplastic elastomeric compounds and viscoelastomeric compounds that include an elastomeric block copolymer component and a plasticizer component. The plasticizer component can include various hydrocarbon molecules that associate with the material into which they are incorporated. The polymeric material can also include various additives in its formulation to obtain specific qualities. 
     The elastomer component of the example polymeric material may include a triblock polymer or copolymer of the general configuration A-B-A, wherein the “A” represents a crystalline polymer, such as a mono alkenylarene polymer, including but not limited to polystyrene and functionalized polystyrene, and the “B” represents an elastomeric polymer such as polyethylene, polybutylene, poly(ethylene/butylene), hydrogenated poly(isoprene), hydrogenated poly(butadiene), hydrogenated poly(isoprene+butadiene), poly(ethylene/propylene), hydrogenated poly(ethylene/butylene+ethylene/propylene), and the like. The “A” components of the polymeric material link to each other to provide strength, while the “B” components provide elasticity. Polymers of a greater molecular weight may be achieved by combining many of the “A” components in the “A” portions of each A-B-A structure, and combining many of the “B” components in the “B” portion of the A-B-A structure, along with the networking of the A-B-A molecules into large polymer networks. 
     The elastomeric “B” portion of the example A-B-A polymers generally has an exceptional affinity for most plasticizing agents, including but not limited to several types of oils, resins, and others. When the network of A-B-A molecules is denatured, plasticizers that have an affinity for the “B” block can readily associate with the “B” blocks. Upon renaturation of the network of A-B-A molecules, the plasticizer remains highly associated with the “B” portions, reducing or even eliminating plasticizer bleed from the material when compared with similar materials in the prior art, even at very high oil:elastomer ratios. 
     The elastomer used in the polymeric material may be an ultra-high molecular weight polystyrene-hydrogenated poly(isoprene+butadiene)-polystyrene, such as those sold under the brand names SEPTON 4045, SEPTON 4055 and SEPTON 4077 by Kuraray America, Inc., which has a place of business in Houston, Tex., an ultra-high molecular weight polystyrene-hydrogenated polyisoprene-polystyrene such as the elastomers made by Kuraray and sold as SEPTON 2005 and SEPTON 2006, or an ultra-high molecular weight polystyrene-hydrogenated polybutadiene-polystyrene, such as that sold as SEPTON 8006 by Kuraray. High to very high molecular weight polystyrene-hydrogenated poly(isoprene+butadiene)-polystyrene elastomers, such as that sold under the trade name SEPTON 4033 by Kuraray, may also be useful in some formulations of the example polymeric material because they may be easier to process than ultra-high molecular weight elastomers due to their effect on the melt viscosity of the material. 
     For examples of suitable elastomeric materials, the methods of making the same, and various suitable configurations for the support substrates  66 ,  72 , reference is additionally made to U.S. Pat. Nos. 3,485,787; 3,676,387; 3,827,999; 4,259,540; 4,351,913; 4,369,284; 4,618,213; 5,262,468; 5,508,334; 5,239,723; 5,475,890; 5,334,646; 5,336,708; 4,432,607; 4,492,428; 4,497,538; 4,509,821; 4,709,982; 4,716,183; 4,798,853; 4,942,270; 5,149,736; 5,331,036; 5,881,409; 5,994,450; 5,749,111; 6,026,527; 6,197,099; 6,843,873; 6,865,759; 7,060,213; 6,413,458; 7,730,566; 7,823,233; 7,827,636; 7,823,234; and 7,964,664, which are all incorporated herein by reference in their entireties. 
     Other formulations of elastomeric materials may also be used in addition to those identified in these patents. As one example, the elastomeric material may be formulated with a weight ratio of oil to polymer of approximately 3.1 to 1. The polymer may be Kraton 1830 available from Kraton Polymers, which has a place of business in Houston. Tex., or it may be another suitable polymer. The oil may be mineral oil, or another suitable oil. One or more stabilizers or a dye may also be added, as well as other additional ingredients. In another example, the elastomeric material may be formulated with a weight ratio of oil to copolymers of approximately 2.6 to 1. 
     In one aspect, the support substrate  66 ,  72  can include a shape conforming medium such as a fluid or a deformable solid that may have a flexible matrix or some degree of flexibility that includes the ferro-magnetic particles. In certain aspects, ferro-magnetic particles can be coated with a compatible polymer that bonds with the Kraton styrene-butadiene-styrene blocks or to the cross-linked chains. Thus, when a current is applied, the chains shorten or become stiff, and changing the elastomeric properties. The particles can be suspended within the mineral oil, and then blended with the Kraton polymer during compounding. 
     With renewed reference to  FIGS.  6 - 7   , the polymeric material of the support substrate  66 ,  72  may be provided as a lattice structure including a plurality of cells  98  including the ferromagnetic particles in the cell walls. The cell walls may be considered as a plurality of upstanding side walls  102  that collectively define a repeating polygonal pattern. 
     As shown in  FIG.  7   , the lattice structure of the support substrate  66 ,  72  may include a number of wires  103  arranged in a predetermined pattern to form a conduit within the support substrate  66 ,  72 . As shown, the wires  103  may be disposed at intersections of adjacent cells  98 , and can collectively form a circuit configured to selectively generate a magnetic field. In other aspects, the wires  103  may be provided surrounding the sides of the cells  98  containing the magnetorheological medium. The wires  103  should be provided at an appropriate gauge thickness such that the passage of an appropriate amount of low voltage current through the wires will provide the necessary magnetic field required to activate the stiffening features of the support substrate  66 ,  72  to provide a desired rigidity. In certain aspects, the wires  103  may be provided wound in a coil shape, or the like, in order to generate a magnetic field. 
     Although shown running in the transverse direction, the wires  103  can additionally or alternatively be arranged in a longitudinal direction, or other desired pattern. In certain aspects, more than one wire  103  may be provided at the intersections. In still other aspects, wires  103  can be provided with a different or tapered gauge thickness, in order to provide a magnetic field of a different magnitude. In still further aspects, different gauge thicknesses and different magnetorheological materials can be used in combination to create different zones or areas that may provide different stiffness features once they are activated. 
     It is also envisioned that one or more electrical conduit can be provided as a separate component, independent from the support substrates. For example, an electrical conduit can be arranged and provided as a two-dimensional, or planar, configuration located adjacent, for example, underneath, the support substrate  66 ,  72 . Such a planar configuration can also be designed with a pattern to provide certain areas with increased or decreased stiffness. In various aspects, the strength of the electrical current, as well as the pattern of the electrical current can be programmed, controlled, monitored, and modified using one or more controller  54 . 
     As shown in  FIG.  7   , the upstanding side walls  102 , as well as the edges  100  of the support substrate may each be defined as having an upper portion  104  that may ultimately be adjacent a patient support surface  38 , and a lower portion  106 , generally opposite from the patient support surface. In various aspects, a thickness of the side wall of the upper portion  104  and a thickness of the lower portion  106  are different. In other aspects, the thickness of the upstanding side walls  102  may be tapered and slightly thinner at the lower portion  106 . In still other aspects, the upper portion  104  and the lower portion  106  may include different magnetorheological materials, and/or contain a different amount of magnetorheological materials. In this regard, it may be feasible to design and obtain a different stiffness in different areas of the walls in order to provide a controlled buckling of the support substrate  66 ,  72 . For example,  FIG.  8    is a partial perspective cross-section view of a support substrate  72  component subjected to pressure from a circular shaped weight  108 , illustrating a buckling of cell walls  102  of the support substrate  72 . As shown, the lower portions  106  of the side walls collapse progressively up to the upper portions  104 . This controlled buckling may help flatten the plateau that is found in the indentation force deflection (IFD) curves. 
       FIG.  9    is a magnified partial cross-sectional view illustrating an interior region  108  of hexagonal shaped cells  98  of an exemplary support substrate  72  component with each cell  98  having a dome top  110  according to various aspects of the present technology. In various aspects, the dome tops  110  may be formed as a single layer shaped and/or welded to the upstanding walls  102  of the cells  98 . In various aspects, the dome tops  110  may include one or more magnetorheological material, for example, provided as one or more layer of a magnetorheological elastomer. In other aspects, the dome tops  110  may be individual components, for example, a separate piece formed with each cell  98  or subsequently attached thereto. In any configuration, the lattice of cells  98  can be designed/tuned with magnetorheological materials to provide an optimal buckling pressure, and the tops  110 , or caps, can be designed/tuned with magnetorheological materials to assist in spreading out the tissue interface pressure (TIP) over a greater surface area. 
       FIG.  10    is a top-side perspective view of a portion of a support substrate component  72  with hexagonal shaped cells  98  and individual shaped tops  112  according to another aspect of the present technology. The tops  112  may be provided with an aperture  114  defined therein to provide fluid communication for air circulation between the cells  98  and the patient support surface  38 . Similar to the dome tops  110  of  FIG.  9   , the tops  112  of  FIG.  10    can also be designed/tuned with magnetorheological materials to assist in spreading out the TIP over a greater surface area. 
       FIGS.  11 A- 11 C  are cross-sectional views of exemplary cells  98  of the support substrate component provided with a dome top  110  as shown in  FIG.  9    ( FIG.  11 A ), a dome top  112  with an aperture  114  as shown in  FIG.  10    ( FIG.  11 B ), and a buttressed dome top  116  with internal supporting features  118  ( FIG.  11 C ). Similar to the dome tops  110 ,  112  of  FIGS.  9  and  10   , the buttressed top  116 , and/or the supporting features  118 , can also be designed/tuned with magnetorheological materials to assist in spreading out the TIP over a greater surface area. 
       FIG.  12    is a top-side perspective view of the exemplary patient support  36  of  FIG.  2    with a plurality of separate zones, or regions  120 , configured to support different areas of a patient body, and/or have a different stiffness.  FIG.  13    is top-side perspective view of the exemplary patient support of  FIG.  12    with a patient  122  resting thereon. By way of example, the patient support  36  may be appropriately segmented by regions  120  shaped and sized for different areas of the human body, such as for: upper/lower legs, knees, ankles, and/or feet; upper/lower arms, elbows, wrists, and/or hands; head, neck, and shoulders; upper and lower abdomen or torso; chest area; and combinations thereof. The regions  120  may further be designed to include inner region portions and outer region portions, such as concentric regions. Regions  120  can also vary in shape and size along a height direction. Different regions  120  may have different lattice structures or cell structures. Different regions can also include different magnetorheological materials, different electromagnets, use different amounts of applied current, be provided with different wiring architectures or circuit designs, and even be provided with the ability to be isolated from a magnetic field. 
     Common regions  120  may be separated into shoulder areas, hip areas, and leg areas. In certain aspects, the different regions  120  are static or permanent and do not change in size or location with respect to the specific patient support. In other aspects, the regions  120  may be designed with an architecture configured to change in size and/or location. For example, a caregiver or a user may be able to input certain information regarding a patient&#39;s age, weight, and height, and with the assistance with a pre-programmed controller using correlated data, the size and/or location of regions  120  may be configured based on patient-specific data. In this regard, for example, the same patient support can be used with a young teenager, as well as a full grown adult, and provide equal benefits to patients of varying size and shape. 
       FIG.  14    is a top-side perspective view of another exemplary patient support apparatus  126  shown with an alternate plurality of separate regions  128  that may be useful with the present technology. As mentioned above, the various regions  128  that may exhibit a different stiffness based on having different magnetic field strengths, or be provided with different magnetorheological materials. In various aspects, the regions  128  may be distinguished from one another as being different thermal zones, and/or different pressure zones. In certain aspects, different thermal zones can be managed by the air circulation device  84  and/or the controller  54 . As mentioned above,  FIG.  14    also illustrates an exemplary circulation device  84  that may be in fluid communication with a least a portion of the patient support  36  mattress. The heat transfer medium used in the circulation device  84  can be a heat transfer fluid or gas, such as air, configured to circulate or flow through at least a portion of the patient support apparatus at a predetermined or otherwise controlled temperature. In the various different aspects, the heat transfer medium serves to alter or maintain a temperature of a surface adjacent to, or an interface in direct contact with, the patient, such as the patient&#39;s skin. 
     In various aspects, the magnetic field can be generated either by an electromagnet or an electrically conductive circuit that is integrated with, or separate and distinct from, the patient support  36 . In one example, with reference to  FIG.  14   , a patient support  36  may be provided with a plurality of electromagnets  130 , each with a capability of generating a magnetic field configured to operate the stiffening features of the respective regions  128  of the patient support  36 . 
     In another specific aspect, a bed component, such as a litter assembly or mattress pad (not shown) that defines a patient support surface  38  of a patient support  36  may be provided with a number of different segmented areas that may each contain an appropriately configured electromagnet (or electrically conductive circuit) strategically disposed therein and configured to generate a suitable magnetic field to work with the support substrates  66 ,  72 . 
     As discussed above, one or more controller  54  ( FIG.  1   ) may be provided to control and manage various aspects of the present technology. For example, the controller  54  may be programmed and configured to monitor and control the electrically conductive conduits  103  and/or electromagnets disposed within, or external from, the support substrate  66 ,  72 , and ultimately provide the appropriate strength of a magnetic field to the magnetorheological material, resulting in a desired level of stiffness and rigidity of the patient support  36 . The controller  54  may also be configured to work with a heat exchanger or the air circulation device  84 , for example, to monitor and/or regulate the heating and cooling thermal management features of the present technology. In certain aspects, the controller  54  may be remotely monitored, operated, or programmed, via an appropriate wired or wireless connection, by a caregiver or medical professional. In certain aspects where the patient support  36  may be used outside of a medical or care facility, the controller  54  may be provided with a portable source of power, such as a battery. In still other aspects, a battery (or other source of electrical current) may be separately provided in order to generate the appropriate magnetic fields. The patient support apparatus  18 , as well as the electromagnet or other source providing the magnetic field may also be managed by the controller  54 . Alternatively, it is also envisioned that the controller  54  can be coupled to, or an integral part of, the patient support apparatus  18 , as shown in  FIG.  1   . 
     In still other aspects, the support substrates  66 ,  72  may be used in combination with one or more shape-memory materials, such as a shape-memory polymer or a shape-memory alloy provided as part of the structure of the support substrate  66 ,  72 . A shape-memory material may also be provided with other components of the patient support  36 , for example, in conjunction with foam bolsters and other cushions or foam components. A shape-memory polymer is a polymer that has the ability to return from a temporary deformed state to its original state when induced by a stimulus, such as a change in temperature. A shape-memory alloy is preferably a lightweight alloy that similarly has the ability to return to its original shape after being deformed, for example, a deformed shape-memory alloy returns to its pre-deformed shape when heated. Non-limiting examples of shape-memory alloys useful with the present technology include copper-aluminum-nickel, and nickel-titanium alloys. 
     In various aspects, the patient support apparatus  18  may include at least one pressure sensor  124  ( FIG.  12   ) strategically located within the patient support  36  and configured to detect a pressure at an interface between the patient support surface  38  and the patient. One or more pressure sensors can be located on a surface of the patient support  36 , as well as disposed at strategic locations within the patient support  36 . In this regard, the controller  54  may be configured to monitor a pressure between the various areas or surfaces of the patient support  36  and the patient. Various temperature sensors (not shown) may also be provided to monitor a temperature of the patient support  36 , a temperature of air circulating within the patient support  36 , as well as a temperature of the patient to ensure proper operation of the patient support apparatus  18  and the various components thereof. In various aspects, heat from the wires  103  or circuits can be used to provide integral thermal management. In still other aspects, the magnetorheological material is thermally conductive and can be used to adjust a temperature of the patient support. 
     The present technology also provides various methods of making a patient support apparatus capable of selectively adjusting a stiffness for redistributing pressure, and methods for adjusting a pressure distribution between a patient and a patient support apparatus. The methods for making the patient support apparatus include integrating a magnetorheological material within a component of the patient support apparatus. As described above, the patient support apparatus will include at least one component defining a patient support surface. At least a portion of the patient support surface will be configured to provide a selectively variable degree of rigidity against a predetermined location of a patient. The methods of making the apparatus include integrating at least one of an electrically conductive circuit and an electromagnet disposed adjacent the magnetorheological material in the patient support apparatus. 
     A controller may be used with the methods for adjusting a pressure distribution between a patient and a patient support apparatus, in particular, to selectively generate a magnetic field, which may be based on patient-specific data, or which may be pre-programmed for certain settings and situations. For example, correlations can be made between the applied current, patient support stiffness, and patient weight in order to provide an optimal pressure redistribution for a patient that can adjust in real time. In various aspects, the patient-specific data is entered by a caregiver, and the system or controller configures appropriate parameters and generates a magnetic field in order to adjust a stiffness of the patient support prior to the patient being placed on the patient support surface. Adjustments can be made at any time. 
     In various aspects, the patient-specific data typically includes the age, weight, and height of the patient. Other data useful for specifically tailoring the stiffness and pressure of the patient support may also include information about pre-existing wounds or pre-existing medical conditions or issues, such as the presence of one or more implant devices; the ability to move or use limbs; the use of prosthetic devices; mental status and cognitive ability; physical therapy requirements; movement restrictions; specific location of bony prominences and wounds; and the like. Pressure map data specific to the patient may also be useful in determining proper pressure redistribution, for example, based on a concentration of TIP. In various aspects, pressure map data can be separately obtained and provided to the system or controller. In other aspects, the patient support apparatus may be configured with the necessary components to obtain pressure map data. 
     The foregoing description is provided for purposes of illustration and description and is in no way intended to limit the disclosure, its application, or uses. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations should not be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure. 
     As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical “or.” It should be understood that the various steps within a method may be executed in different order without altering the principles of the present disclosure. Disclosure of ranges includes disclosure of all ranges and subdivided ranges within the entire range, including the endpoints. 
     As used herein, the terms “comprise” and “include” and their variants are intended to be non-limiting, such that recitation of items in succession or a list is not to the exclusion of other like items that may also be useful in the devices and methods of this technology. Similarly, the terms “can” and “may” and their variants are intended to be non-limiting, such that recitation that an embodiment can or may comprise certain elements or features does not exclude other embodiments of the present technology that do not contain those elements or features. 
     The broad teachings of the present disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the specification and the following claims. Reference herein to one aspect, or various aspects means that a particular feature, structure, or characteristic described in connection with an embodiment or particular system is included in at least one embodiment or aspect. The appearances of the phrase “in one aspect” (or variations thereof) are not necessarily referring to the same aspect or embodiment. It should be also understood that the various method steps discussed herein do not have to be carried out in the same order as depicted, and not each method step is required in each aspect or embodiment.