Patent Publication Number: US-2022212804-A1

Title: Shape memory alloy (sma) passive temperature control systems and methods for aircraft electrical systems

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to electrical systems of aircraft. More specifically, aspects of this disclosure relate to thermal management systems and methods for passive cooling of battery modules and electrical hardware of unmanned aerial vehicles. 
     BACKGROUND 
     Many commercially available UAVs employ a rechargeable battery module to store and supply the requisite power for operating the electric motor unit or units used to propel the aircraft. In order to generate power with sufficient flight range without drastically increasing the aircraft&#39;s all-up weight (AUW), each battery module is smaller yet significantly more powerful and higher in capacity (Amp-hr) than a standard 12-volt lead-acid battery. Modern UAV battery packs group stacks of discretely packaged battery cells into one or more individual battery modules that are mounted onto the airframe, e.g., inside a dedicated compartment or on a load-bearing support tray. A high-voltage electrical system governs the transfer of electricity between the battery module(s) and electric motor(s). The electric system may employ a front-end DC-to-DC power converter that increases the pack voltage supply to a main direct current (DC) bus and a power inverter module (PIM). Operation and control of each electric motor unit may be accomplished by employing the PIM to transform DC electric power to alternating current (AC) power using pulse-width modulated control signals output from a Battery Pack Controller (BPC). 
     SUMMARY 
     Presented herein are passive temperature control systems for thermal management of electrical systems, methods for making and methods for using such temperature control systems, and aircraft equipped with smart-material activated temperature control systems for passive cooling of battery modules. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an elevated, perspective-view illustration of a representative aircraft with a rechargeable battery module in accordance with aspects of the present disclosure. 
         FIGS. 2A and 2B  are schematic, side-view illustrations of a representative smart-material activated passive temperature control system for thermal management of an electrical component in an electrical system in accord with aspects of the disclosed concepts. 
         FIGS. 3A and 3B  are schematic, side-view illustrations of a representative SMA thermal management system for passive cooling of a rechargeable battery module of an aircraft in accord with aspects of the disclosed concepts. 
     
    
    
     The present disclosure is amenable to various modifications and alternative forms, and some representative embodiments are shown by way of example in the drawings and will be described in detail below. It should be understood, however, that the novel aspects of this disclosure are not limited to the particular forms illustrated in the above-enumerated drawings. Rather, the disclosure is to cover all modifications, equivalents, combinations, subcombinations, permutations, groupings, and alternatives falling within the scope of this disclosure as encompassed, for example, by the appended claims. 
     DETAILED DESCRIPTION 
     This disclosure is susceptible of embodiment in many different forms. Representative examples of the disclosure are shown in the drawings and herein described in detail with the understanding that these embodiments are provided as an exemplification of the disclosed principles, not limitations of the broad aspects of the disclosure. To that end, elements and limitations that are described, for example, in the Abstract, Technical Field, Background, Summary, Description of the Drawings, and Detailed Description sections, but not explicitly set forth in the claims, should not be incorporated into the claims, singly or collectively, by implication, inference or otherwise. Moreover, the drawings discussed herein are not necessarily to scale and are provided purely for instructional purposes. Thus, the specific and relative dimensions shown in the drawings are not to be construed as limiting. 
     For purposes of the present detailed description, unless specifically disclaimed: the singular includes the plural and vice versa; the words “and” and “or” shall be both conjunctive and disjunctive; the words “any” and “all” shall both mean “any and all”; and the words “including,” “containing,” “comprising,” “having,” and the like, shall each mean “including without limitation.” Moreover, words of approximation, such as “about,” “almost,” “substantially,” “generally,” “approximately,” and the like, may each be used herein in the sense of “at, near, or nearly at,” or “within 0-5% of,” or “within acceptable manufacturing tolerances,” or any logical combination thereof, for example. Lastly, directional adjectives and adverbs, such as fore, aft, inboard, outboard, starboard, port, vertical, horizontal, front, back, left, right, etc., may be with respect to an aircraft that is operatively oriented in an upright position on a horizontal support surface. 
     Referring now to the drawings, wherein like reference numbers refer to like features throughout the several views, there is shown in  FIG. 1  a representative aircraft, which is designated generally at  100  and portrayed herein for purposes of discussion as a multi-rotor vertical takeoff and landing unmanned aerial vehicle. The illustrated VTOL aircraft  100 —also referred to herein as “vehicle” or “UAV” for brevity—is merely an exemplary application with which aspects and features of this disclosure may be practiced. In the same vein, utilization of the present concepts for passive cooling of a UAV battery module should also be appreciated as an exemplary implementation of the concepts disclosed herein. As such, it will be understood that aspects of the present disclosure may be implemented for cooling other electrical system hardware and architectures, may be incorporated into any logically relevant type of aircraft, and may be utilized in both vehicular and non-vehicular applications alike. Lastly, only select components have been shown and will be described in additional detail herein. Nevertheless, the systems, methods, devices, and aircraft discussed below may include numerous additional and alternative features, and other available peripheral components, for carrying out the various functions of this disclosure. 
     UAV  100  of  FIG. 1  is shown as a cargo drone with a load-bearing airframe  102  that is generally composed of a central fuselage  104  and a circular array of (six) rotor booms  106 . Projecting orthogonally from a terminal end of each boom  106  is a fixed skid-type landing gear  110 . Also cantilevered to the fuselage  104  at the terminal ends of the booms  106  are motor-driven rotor assemblies  108 . While a six-rotor (hexarotor) cargo drone is illustrated in the Figures, the UAV  100  may take on alternative aircraft configurations and size classifications, may employ greater or fewer than six rotors, and may employ various control surfaces and lifting surfaces. 
     Rotor assemblies  108  of  FIG. 1  may be operated individually, jointly, and in assorted combinations to provide lift and thrust to the UAV  100 . Each rotor assembly  108  may be typified by a lift motor  112  that drives a multi-blade propeller assembly  114  mounted at a distal end of a mast shaft (not visible). These hingeless “simple” rotor assemblies  108  are each juxtaposed with a landing gear  110  at the distal end of a rotor boom  106  and vertically oriented to direct thrust forces downward relative to the airframe  102 . The lift motors  112  may be embodied as brushless permanent magnet (PM) electric motors controlled via an electronic speed controller (ESC)  116  ( FIG. 2 ). While shown packaged at the distal end of each boom  106 , the six lift motors  112  (or a single, shared lift motor) may instead be located on the fuselage  104  of the airframe  102 . As a further option, torque generated via a lift motor  112  may be transmitted to one or more propeller assemblies  114  via a drive belt/chain, gearbox, or power-shifted transmission interposed between the motor  112  and propeller(s)  114 . Propeller assembly  114  speed and, thus, rotor assembly  108  output may be controlled by modulating power supplied to each lift motor  112  from a resident rechargeable energy storage system (RESS), represented in  FIG. 1  as a lithium-ion (Li-ion) or silicon-based Li-ion (secondary) battery module  142 . 
     At present, many commercially available UAVs do not offer thermal management for the electrical hardware components of the aircraft&#39;s electrical system. Some UAVs rely on thermal inertia of the battery module and module housing to limit spikes in battery cell temperature. Convective (air) cooling, liquid (water/glycol) cooling, and compressor-based (refrigerant) cooling are other available techniques that may be used for heat abatement in UAV applications. Such passive cooling systems, however, have low heat transfer coefficient and, thus, are unable to cope with high current draw systems, which may lead to poor battery efficiency and irrecoverable capacity fade over the life of a battery module. Likewise, many available active cooling systems are not practical due to UAV packaging and weight constraints, and are prone to multiple failure paths due to the use of dedicated electronic and moving parts. 
     Presented herein are smart-material activated passive temperature control systems for thermal management of electrical systems.  FIGS. 2A and 2B  and  FIGS. 3A and 3B , for example, illustrate two examples of thermal management systems  200  and  300 , respectively, for passive cooling of an electrical system component of a vehicle, such as rechargeable battery module  142  of UAV  100  in  FIG. 1 . While differing in appearance, it is envisioned that the features and options disclosed herein with reference to the thermal management system  200  of  FIGS. 2A and 2B  may be incorporated, singly or in any combination, into the example thermal management system  300  of  FIGS. 3A and 3B , and vice versa. As a point of similarity, both thermal management systems  200 ,  300  are portrayed cooling a respective rechargeable battery module  210  and  310 . Each battery module  210 ,  310  may include a stack of electrochemical battery cells, such as secondary lithium ion (Li-ion) or Li-ion polymer (LiPo) soft polymer pouch cells  212  and  312 . Both battery modules  210 ,  310  store their electrochemical battery cells  212 ,  312  inside a protective, electrically insulating battery module housing  214  and  314 , respectively. For simplification of design and maintenance, and for reduction in cost and assembly time, each battery cell in the RESS may be substantially identical to one another. It is also envisioned that the thermal management systems  200 ,  300  be utilized to cool multiple battery modules (e.g., within a battery pack) and/or other electrical components (e.g., aircraft CPU  118 , memory  122 , flight controller  124 , etc.) in an electrical system. 
     Movably mounted adjacent the module housing  214 ,  314  is a cooling chamber  216  and  316  that selectively thermally interfaces with and, when operatively attached, cools the battery cells  212 ,  312  packaged inside the housing  214 ,  314 . It may be desirable that the cooling chamber  216 ,  316  be fabricated as a light-weight, liquid-sealed container with excellent mechanical and chemical resistance properties that are retained from ambient to high temperatures. For instance, the cooling chamber  216 ,  316  may be formed from one or more of: a thermally conductive, lightweight pitch-based carbon fiber; titanium, aluminum alloy, or other lightweight, strong, and corrosion-resistant metal or metal alloy; or polyether ether ketone (PEEK) thermoplastic polymer or other suitable polymeric materials. The thermal management system  300  may be equipped with a pressure relief valve  324  or similarly suitable venting device through which gaseous byproducts may be expelled from the cooling chamber  316 . It should be appreciated that the size and shape of the cooling chamber  216 ,  316  may be altered and scaled, for example, to accommodate alternative applications and/or desired packaging constraints. In addition, while shown translating rectilinearly toward and away from the module housing  214 ,  314  (e.g., up and down in  FIGS. 2B and 3B ), the cooling chamber  216 ,  316  may rotate or slide into contact with the module housing  214 ,  314 , e.g., in clamshell or slide top arrangements. 
     A hydrophobic melamine foam  218  may be disposed within the cooling chamber  216 , located above and extending across a sublimable cooling agent  220 , for improved chamber insulation and venting of sublimation gases. Potentially offering improved thermal contact and device-agnostic acceleration, the hydrophobic melamine foam  218  may have a density of approximately 0.31 to 0.45 lbs/ft 3 , a temperature range of about −300° F. to about +360° F., and a thermal conductivity of about 0.2 to 0.3 BTU-in/hr ft 2 -hr-° F. at approximately 70° F. As an alternative, a polystyrene foam or paper-based insulation jacket  318  may be used to cover a sublimable cooling agent  320  within the cooling chamber  316 . For at least some configurations, such as those in which substantially all non-interfacing segments of the cooling chamber  216 ,  316  are formed from a thermally insulating material, a thermally conductive (bottom) wall  222  may be mounted to the cooling chamber  216 , e.g., along an underside thereof, to contact and thereby thermally interface with a complementary thermally conductive (top) cover  224  of the module housing  214 , as best seen in  FIG. 3B . 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Cooling Agent 
                 Additive 
               
               
                   
                   
               
             
            
               
                   
                 dry ice 
                 formamide 
               
               
                   
                 dry ice 
                 cyclohexane 
               
               
                   
                 dry ice 
                 benzene 
               
               
                   
                 dry ice 
                 dioxane 
               
               
                   
                 dry ice 
                 carbon tetrachloride 
               
               
                   
                 liquid N 2   
                 n-butanol 
               
               
                   
                 liquid N 2   
                 vexane 
               
               
                   
                 liquid N 2   
                 ethyl acetate 
               
               
                   
                 liquid N 2   
                 cycloheptane 
               
               
                   
                   
               
            
           
         
       
     
     For enhanced cell safety, increased operational life expectancy, and ameliorated battery thermal limits, the cooling chambers  216 ,  316  of  FIGS. 2A-2B and 3A-3B  securely store a sublimable cooling agent  220 ,  320  (i.e., a coolant material capable of sublimation). In accord with the illustrated examples, the sublimable cooling agent  220 ,  320  is composed of a solid-form carbon dioxide material (i.e., dry ice) as a heat sink with a relatively large energy density. To improve the cooling proficiency of dry ice, the sublimable cooling agent  220  may optionally be partially or wholly immersed within a non-toxic and non-flammable dry cleaning fluid  230 . By way of non-limiting example, the dry-cleaning fluid  230  may include: a tetrachloroethylene-based solvent; a petroleum-based hydrocarbon solvent; and/or a trichloroethylene-based solvent. Additional examples of appropriate cooling agent mixtures are provided above in Table 1. An advantage of solid-form carbon dioxide is that the sublimation enthalpy of dry ice is three to four times that of comparable phase change materials. Additionally, the cooling temperatures of dry ice are markedly lower than other alternative options, offering a significantly larger resultant temperature delta and, thus, increased cooling efficiency. 
     In order to prevent overcooling of the battery cells  212  via the sublimable cooling agent  220 , one or more biasing members may separate the cooling chamber  216  from the module housing  214 . With reference again to  FIGS. 2A and 2B , the biasing member may take on the form of a return spring  232  that is mounted to an underside, module-facing surface of the cooling chamber  216 . The illustrated return spring  232  is a helical compression spring that projects generally orthogonally from the cooling chamber  216  and presses against a topside, chamber-facing surface of the module housing  214 . With this arrangement, the return spring  232  is able to maintain a desired minimum gap distance between the module housing  214  and cooling chamber  216  when the battery cells  212  are operating within a calibrated acceptable operating temperature range. While shown as a single biasing member in the form of a helical compression spring, the thermal management system  200  may employ multiple return springs  232 , which may be similar or dissimilar in type and location from what is shown in the drawings. For instance, the biasing member may be a leaf spring, a torsional spring, a tension spring, or a pneumatic cylinder, and may be located along other faces of the cooling chamber  216 . Alternatively, the thermal management system  300  of  FIGS. 3A and 3B  altogether omits a biasing member and relies, for example, on the spring force of the smart material actuators discussed below to bias the cooling chamber  316  away from the module housing  314 . 
     A smart-material actuator extends between and operatively connects the thermal management system  200 ,  300  to the battery module  210 ,  310  to enable selective thermal communication between the cooling chamber  216 ,  316  and the module housing  214 ,  314 . According to the illustrated example, a smart material actuator in the form of at least one shape memory alloy (SMA) spring  234 ,  334  is attached to the cooling chamber  216 ,  316  and thermally interfaces with the module housing  214 ,  314 . A square array of SMA springs  234 ,  334  may be sandwiched between the thermal management system  200 ,  300  and battery module  210 ,  310 , mounted to the underside, module-facing surface of the cooling chamber  216  and to the topside, chamber-facing surface of the module housing  214 . Similar to the return spring  232 , the SMA springs  234 ,  334  of  FIGS. 2A-2B and 3A-3B  are portrayed as helical compression springs that project generally orthogonally from the cooling chamber  216  and press against an opposing surface of the module housing  214 . As an alternative to SMA springs, selective thermal communication between the cooling chamber  216 ,  316  and the module housing  214 ,  314  may be enabled by different smart materials, such as a shape memory polymer (SMP), a magneto-caloric alloy, thermoelectric materials, etc., and by different actuator configurations, such as leaf springs, torsional springs, engineered control arms, linear cylindrical actuators, etc. 
     Each SMA spring  234 ,  334 , through contact with the battery module  210 ,  310 , extracts thermal energy from the module housing  214 ,  314 . Once heated to a phase transformation temperature (e.g., an austenite temperature A f  at which the alloy transforms from martensite to austenite), the SMA spring  234 ,  334  automatically change shape. SMA springs  234  of  FIGS. 2A-2B  may contract and concomitantly generate a tensile spring force that pulls the cooling chamber  216  into contact with the module housing  214 . Alternatively, SMA springs  334  of  FIGS. 3A-3B , upon reaching the phase transformation temperature, may collapse and, thus, allow the cooling chamber  216  to descend, under the force of gravity, into contact with the module housing  214 . As described above, contact between the thermally conductive wall  222  of the cooling chamber  216  with the thermally conductive cover  224  of the module housing  214  will enable thermal heat transfer from the battery cells  212  to the sublimable cooling agent  220 . Embodiments employing thermally conductive module housings and chambers may eliminate the need for add-on thermal plates such that direct module-to-chamber contact will enable thermal exchanges. 
     Once sufficiently cooled (e.g., to a martensite temperature M f ), the SMA springs  234  return to their original, expanded state; the return spring  232  of  FIGS. 2A-2B  takes over and biases the cooling chamber  216  away from the module housing  214 . On the other hand, SMA springs  334  of  FIGS. 3A-3B , when sufficiently cooled, return to their original, expanded state and concomitantly generate a sufficient compressive force against the battery module  310  to push the cooling chamber  316  away from the module housing  314 . An optional thermal grease  236  may be applied onto the distal ends of the SMA springs  234 ; the thermal grease  236  contacts the module housing  214  and enhances the thermal interface between the SMA springs  234  and housing  214 . As yet another option, a thermally insulated stub  238  may be attached to the proximal ends of the SMA springs  234 . These thermally insulated stubs  238  are interposed between and, thus, thermally isolate the SMA springs  234  and the cooling chamber  216 . 
     With reference again to  FIGS. 2A and 2B , the battery cells  212  of battery module  210  may be partially or wholly submerged in a dielectric fluid  240  that partially fills the interior cell chamber of the module housing  214 . This dielectric fluid  240  may be in the nature of a non-flammable, immersion-cooling engineered liquid (e.g., NOVEC™ 7000 or ELECTROCOOL®) that extracts heat energy generated by the discharging battery cells  212 . Once heated by the battery cells  212  to a predefined temperature, the dielectric fluid  240  evaporates. A series of thermally conductive fins  242  are each attached to a respective battery cell  212  inside the module housing  214 . These fins  242  thermally couple with the cover  224  of the module housing  214  and, optionally, contact a thermally conductive fin  226  projecting from the cooling chamber  216 . Through this mechanical interface, the sublimable cooling agent  220  inside the cooling chamber  216  extracts heat from and cools the fins  242 . The cooled thermally conductive fins  242 , in turn, contact and condense the evaporated dielectric fluid  240 ; the condensed, liquid fluid  240  then returns to the liquid volume to extract addition heat energy from the battery cells  212 . Each battery cell  212  may be packed inside a wicking jacket  244  to improve surface wetting of the cells  212  and to protect the cells  212  against acceleration and negative g forces. As a further option, a porous insert layer  246  may be inserted between neighboring battery cells  212 . The porous insert layer  246 , which may be formed from expandable graphite or carbon foam, helps to improve nucleation, facilitate efficient boiling, and reduce charge of the dielectric fluid  240 . 
     Further, the disclosure comprises embodiments according to the following clauses: 
     Clause 1: a thermal management system for an electrical component, the electrical component stored inside a module housing, the thermal management system including: a cooling chamber configured to movably attach adjacent the module housing, the cooling chamber configured to contain therein a sublimable cooling agent; a biasing member configured to bias the cooling chamber away from the module housing; and a smart material actuator attached to the cooling chamber and configured to thermally interface with the module housing, the smart material actuator being configured to extract thermal energy from the module housing and, once heated to a phase transformation temperature, selectively actuate to thereby move the cooling chamber into contact with the module housing. 
     Clause 2: the thermal management system of clause 1, wherein the smart material actuator includes a shape memory alloy (SMA) spring mounted to the cooling chamber and configured to attach to the module housing. 
     Clause 3: the thermal management system of clause 2, wherein the SMA spring includes a pair of SMA helical springs projecting from a module-facing surface of the cooling chamber. 
     Clause 4: the thermal management system of clauses 2 or 3, further comprising a thermal grease located on a distal end of the SMA spring and configured to contact the module housing. 
     Clause 5: the thermal management system of any one of clauses 2 to 4, further comprising a thermally insulated stub attached to a proximal end of the SMA spring and interposed between the SMA spring and the cooling chamber. 
     Clause 6: the thermal management system of any one of clauses 2 to 5, further comprising a hydrophobic melamine foam disposed within the cooling chamber. 
     Clause 7: the thermal management system of any one of clauses 1 to 6, wherein the sublimable cooling agent includes a solid-form carbon dioxide. 
     Clause 8: the thermal management system of clause 7, wherein the sublimable cooling agent further includes a non-toxic and non-flammable dry cleaning fluid within which is disposed the solid-form carbon dioxide. 
     Clause 9: the thermal management system of clause 8, wherein the dry cleaning fluid includes a tetrachloroethylene-based solvent, a petroleum-based hydrocarbon solvent, a trichloroethylene-based solvent, or a combination of two or more thereof. 
     Clause 10: the thermal management system of any one of clauses 1 to 9, further comprising a plurality of thermally conductive fins attached to the cooling chamber and configured to insert into the module housing to thereby thermally couple the sublimable cooling agent with the electrical component. 
     Clause 11: the thermal management system of clause 10, wherein the electrical component includes a battery module with multiple battery cells disposed within the module housing and at least partially submerged in a dielectric fluid, the dielectric fluid being configured to extract heat energy from the battery cells and evaporate once heated to a predefined temperature, and wherein the thermally conductive fins are configured to condense the evaporated dielectric fluid upon contact therewith and transfer the extracted heat energy to the sublimable cooling agent. 
     Clause 12: the thermal management system of any one of clauses 1 to 11, wherein the cooling chamber includes a thermally conductive wall configured to contact and thereby thermally interface with the module housing upon contraction of the smart material actuator. 
     Clause 13: the thermal management system of any one of clauses 1 to 12, wherein the biasing member is mounted to the cooling chamber and configured to press against the module housing, the biasing member including one or more helical compression springs projecting from a module-facing surface of the cooling chamber. 
     Clause 14: an aircraft including: an airframe; a rotor assembly and/or a pair of wings attached to the airframe; an electrical system including a battery module with a module housing mounted to the airframe and multiple battery cells disposed within the module housing; and a thermal management system including: a cooling chamber movably mounted to the airframe adjacent the module housing, the cooling chamber containing therein a sublimable cooling agent; a biasing member projecting from a module-facing surface of the cooling chamber and pressing against a chamber-facing surface of the module housing to thereby bias the module housing away from the cooling chamber; and a smart material actuator mounted to the cooling chamber and thermally interfacing with the module housing, the smart material actuator being configured to extract thermal energy from the module housing and, once heated to a phase transformation temperature, selectively contract to thereby pull the cooling chamber into contact with the module housing. 
     Clause 15: a method of cooling an electrical component, the electrical component stored inside a module housing, the method including: movably attaching a cooling chamber adjacent the module housing, the cooling chamber containing therein a sublimable cooling agent; biasing the cooling chamber away from the module housing via a biasing member; selectively actuating a smart material actuator attached to the cooling chamber by thermally interfacing the smart material actuator with the module housing such that the smart material actuator extracts thermal energy from the module housing; moving the cooling chamber into contact with the module housing via the smart material actuator being heated to a phase transformation temperature and thereby changing shape; and extracting thermal energy from the module housing via the sublimable cooling agent by contacting the cooling chamber with the module housing. 
     Clause 16: the method of clause 15, wherein the smart material actuator includes a shape memory alloy (SMA) spring mounted to the cooling chamber and configured to attach to the module housing. 
     Clause 17: the method of clauses 15 or 16, wherein the sublimable cooling agent includes a solid-form carbon dioxide. 
     Clause 18: the method of clause 17, wherein the sublimable cooling agent further includes a non-toxic and non-flammable dry cleaning fluid within which is disposed the solid-form carbon dioxide. 
     Clause 19: the method of any one of clauses 15 to 18, wherein the cooling chamber includes a plurality of thermally conductive fins, and wherein extracting thermal energy from the module housing further includes inserting the thermally conductive fins into the module housing to thereby thermally couple the sublimable cooling agent with the electrical component. 
     Clause 20: the method of clause 19, wherein the electrical component includes a battery module with multiple battery cells disposed within the module housing and at least partially submerged in a dielectric fluid, the dielectric fluid being configured to extract heat energy from the battery cells and evaporate once heated to a predefined temperature, and wherein the thermally conductive fins are configured to condense the evaporated dielectric fluid upon contact therewith and transfer the extracted heat energy to the sublimable cooling agent. 
     Aspects of the present disclosure have been described in detail with reference to the illustrated embodiments; those skilled in the art will recognize, however, that many modifications may be made thereto without departing from the scope of the present disclosure. The present disclosure is not limited to the precise construction and compositions disclosed herein; any and all modifications, changes, and variations apparent from the foregoing descriptions are within the scope of the disclosure as defined by the appended claims. Moreover, the present concepts expressly include any and all combinations and subcombinations of the preceding elements and features.