ELECTROCOMPACTED AND ELECTROSPUN LEATHER AND METHODS OF FABRICATION

Abstract

Biofabricated leathers made by electrocompaction and/or electrospsinning. Described herein are biofabricated leather materials derived from electrospun or electrocompacted collagen networks. These electrospun or electrocompacted leathers may have leather-like properties following and are may be processed as native leather and used to form leather goods.

Claims

1. A method for making an electrocompacted leather material, the method comprising: applying a solution of non-human, monomeric collagen onto an electrocompaction surface; compacting the protein into a dense network with an electrical field; inducing fibrillation of the protein; incorporating lubricant in the network; and removing water from the network.

2. The method of claim 1, wherein the collagen monomers are polymerized into dimers, trimers and higher order oligomers prior to compaction and fibrillation.

3. The method of claim 1, further comprising adding a crosslinking agent to the aqueous solution to stabilize the collagen fibrils.

4. The method of claim 1, further comprising reacting the collagen fibrils with a dewatering agent to displace water bound to the collagen fibrils with the dewatering and coalescing agent.

5. The method of claim 4, wherein the dewatering agent is a sulfonated condensation product of an aromatic compound.

6. The method of claim 1, wherein fibrillation is induced through the addition of salts such as sodium phosphate, potassium phosphate, potassium chloride and sodium chloride.

7. The method of claim 1, wherein fibrillation is induced through a pH shift following the addition of acids or bases such as sodium carbonate, sodium bicarbonate and sodium hydroxide.

8. The method of claim 1, wherein fibrillation is induced through the incorporation of nucleation agents such as collagen microgels, microparticles, nanoparticles, and natural and synthetic microfibers.

9. The method of claim 1, wherein collagen fibrils are chemically modified to promote chemical or physical crosslinking between collagen fibrils.

10. The method of claim 1, wherein stabilization of the fibrillar collagen network is accomplished through incorporating molecules with di, tri and multifunctional reactive groups such as chromium, amine, carboxylic acid, sulfate, sulfite, sulfonate, aldehyde, hydrazide, sulfhydryl, diazirine, aryl-azide, acrylate, epoxide, or phenol.

11. The method of claim 1, wherein the fibrillated collagen is stabilized through chromium, aldehyde or vegetable tannin based tanning processes.

12. The method of claim 1, wherein water is removed from the fibrillated collagen through solvent exchanges with solvents such as acetone, ethanol, or diethyl ether.

13. The method of claim 1, wherein water is removed from the fibrillated collagen through air or vacuum drying.

14. The method of claim 1, wherein at least 80% of the water is removed from the fibrillated collagen

15. The method of claim 1, wherein lubricating fats and oils are uniformly incorporated into the material.

16. The method of claim 1, wherein the collagen monomers are recombinant collagen.

17. The method of claim 1, wherein the collagen monomers are type 3 collagen.

18. The method of claim 1, wherein the fibrils are 1 nm to 1 μm in diameter

19. The method of claim 1, wherein the fibrils are 100 nm to 1 mm in length

20. The method of claim 1, wherein the fibril network lacks higher order fiber and fiber bundle organization.

21. The method of claim 1, wherein the fibril density is 5 mg/cc to 500 mg/cc

22. The method of claim 1, wherein the thickness is 0.05 mm to 2 mm.

23. A method for making an electrocompacted leather material, the method comprising: applying a solution of non-human, monomeric collagen in an aqueous buffer onto an electrocompaction surface, wherein the solution is substantially free of collagen fibers and fibril bundles; compacting the collagen into a dense network with an electrical field; inducing fibrillation of the collagen to form collagen fibrils; stabilizing the fibrillar collagen network; incorporating lubricant in the collagen network; dyeing and applying a surface finish on the collagen network; and removing water from the stabilized network and drying the collagen network.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1 is a drawing showing the composition of collagen in a hierarchical fashion. 1) shows each collagen molecule and how they are packed with respect to neighboring collagen molecules; 2) shows stacked collagen that make up collagen fibers; 3) shows a cross-section of the collagen fibrils; 4) shows collagen fibers; and 5shows bundles of collagen fibers.

[0040] FIG. 2 is a picture showing the composition of buffalo hide. The top grain layer and the corium layer underneath are shown and the relative amount of collagen fiber bundles are indicated.

[0041] FIGS. 3A-3C illustrate the electrocompaction of collagen. FIG. 3A shows a compaction cell with the silicone spacers. FIG. 3B shows an assembled cell with collagen solution between the plates before and after assembly. FIG. 3C shows compacted and fibrillated collagen matrix, forming a gel. The gels become opaque after fibrillation.

[0042] FIGS. 4A and 4B is a transmission electron micrographs (TEM) of electrocompacted collagen material (e.g., which may be referred to as a hydrogel) before (FIG. 4A) and after (FIG. 4B) fibrillation. The presence of periodic dark bands in FIG. 4B indicate the presence of fibrils.

[0043] FIGS. 5A and 5B show a scanning electron micrographs (SEM) of bovine grain (FIG. 5A, on the bottom) and electrocompacted collagen (FIG. 5B) at two magnifications. The dense fibrillar network indicates assembly of collagen into a network similar to the grain of genuine leather. FIG. 5A is adapted from “Structure of bovine skin and hair root,” Matthias Wagner and David Bailey, TFL.

[0044] FIG. 6 is a strain-stress graph of the dried electrocompacted collagen material following fatliquoring with different materials. Lipoderm A1 fatliquor provides more internal lubrication than cod liver oil, indicated by the increase in both tensile strength and elongation, preventing fibers to stick, known to result in a brittle material.

[0045] FIG. 7A illustrates the generic technique for electrospinning, showing the use of appositive high voltage load to spin a solution of material (e.g. collagen) onto a target.

[0046] FIG. 7B shows another illustration of electrospinning to form fibers that may be deposited onto a target.

[0047] FIGS. 8A-8D illustrate prior art examples of networks of fibers obtained by electrospinning. In FIG. 8A (adapted from Zhou J, Sui F, Yao M et al., Neural Regeneration Research, 2013 8(16): 1455-1464) oriented (on left) and random (right) deposition of collagen nano-fibers is shown. FIGS. 8B-8D show example of mono (FIG. 8B) and bi-layered (FIG. 8C and larger magnification view in FIG. 8D) collagen fibers are shown.

[0048] FIG. 9A illustrates one example of a collagen network formed by electrospinning at two magnifications. Any appropriate thickness of collagen network may be formed in this manner.

[0049] FIG. 9B illustrates a cross-linked (by addition of DHT) electrospun collagen network at two magnifications.

[0050] FIG. 9C is a table comparing the stability of non- (or pre-) cross-linked and cross-linked collagen networks such as those shown in FIGS. 9A and 9B in various solvents.

[0051] FIG. 9D shows exemplary fiber dimensions (diameter, planar density and thicknesses) for the electrospun collagen networks (forming electrospun leather) as described herein. Any appropriate range of collagen fiber dimensions may be formed.

[0052] FIG. 10 shows exemplary images of electrospun collagen networks (forming electrospun leather materials) before, during and after fatliquoring in non-cross-linked and cross-linked samples.

[0053] FIG. 11 is a table illustrating weights in an example of different electrospun leathers that are ether cross-linked or non-cross-linked before and after fatliquoring.

[0054] FIGS. 12A-12D illustrate mechanical properties of electrospun leather fabricated as described herein before and after fat liquoring in ethanol/cod oil (e.g., 80/20).

[0055] FIGS. 13A and 13B show mechanical properties of electrospun leather before and after fatliquoring in ethanol/casterol oil (80/20). FIG. 13A shows elongate percent and FIG. 13B shows tensile strength.

DETAILED DESCRIPTION

[0056] In general, described herein are methods of forming biofabricated leather materials from a solution of, e.g., monomeric, collagen by elctrocompaction and/or electrospinning. The resulting material may be referred to as electrocompacted leather material or electrospun leather. Also described herein are the resulting materials, which may be structurally (including ultrastructurally) and/or compositionally distinct from native (e.g., “natural” leathers) and other man-made leather materials.

[0057] Reconstituted collagen networks have been widely employed in biomedical applications, regenerative medicine and tissue engineering, however to date such reconstituted collagen networks have not been made into leathers that may be used in place of natural leather. For example, collagen may be obtained from animal tissues known to be abundant in collagen type I (such as tendons and skin) via acid extraction and/or enzymatic digestion, purified and stored in a weak acidic solution, consisting of mixtures of monomers, dimers and trimers of the collagen triple helix. Fibrillogenesis may be initiated by adjusting the pH and ionic strength of the solution; the monomers either self-assemble into fibrils and/or connect through chemical crosslinkers forming a fibril matrix. Fibril formation is not restricted to full length, extracted collagen monomers only: recombinant collagen and collagen-like proteins (often truncated) fibrillate in a similar way when pH and ionic strength is optimized. This method has a disadvantage in manufacturing gels of high concentration and orientation of fibers, collagen concentration in animal hide is around 200-300 mg/ml. To attain such density further processing may be required, such as drying and mechanical compaction as described herein.

[0058] Collagen matrices (including hydrogels) of high density and orientation may be manufactured via isoelectric focusing. This method may rely on the concentration of ampholytic molecules such as collagen by manipulating the electrochemical environment of collagen in a solution. Briefly, collagen may be extracted from animal tissues as mentioned before, purified, then dialyzed against deionized water, removing salts and acids. The solution may be poured between two linear or planar electrodes and an electric field and current is applied across the collagen solution, resulting in a pH gradient. The collagen molecules may then migrate and accumulate either in a narrow string (linear electrodes) or in a plane (planar electrodes) at a pH value corresponding to their isoelectric point. The duration of the migration and the thickness of the assembling collagen layer may depend on the voltage applied, as well as the distance between the plates. When migration ceases (indicated by a more or less stable current) the resulted collagen structure is removed and placed in an aqueous environment where adjustment of pH and ionic strength will promote fibrillogenesis and crosslinking yielding in a highly compacted, dense collagen matrix.

[0059] Without substantial modification, such materials (e.g., gels) may be suitable for research and development performing basic research in cell and matrix biology (including tissue engineering and regenerative medicine), however they are not usually appropriate, without significant further processing, to form leather. Described herein are leather-like material (engineered leather/biofabricated leather) and methods for forming such leather-like materials for consumer use using electrocompacted and/or electrospun collagen networks.

Electrocompaction

[0060] The biomaterials described herein that possess leather-like properties, may be formed from an electrocompacted and fibrillated collagen which is further cross-linked and lubricated at the structural fibril level, similar to tanned natural leather. This approach produces leather-like material similar to a leather grain, offering tunability across a wide range of properties (structure, strength, elongation, density, etc.) and it is not restrictive to collagen type I found in animal hide, a limitation of the traditional leather industry.

[0061] For example, in general a method for making an electrocompacted leather material may include: applying a solution of dissolved protein in aqueous buffer onto an electrocompaction surface; compacting the protein into a dense network with an electrical field; inducing fibrillation of the protein; removing water from the network; and incorporating lubricant in the network. The protein may be any appropriate protein, including collagen (any of the known 28+ types of collagen and variations thereof) and non-collagen proteins that may form (e.g., by self-assembly) fibrils, such as, e.g., keratin, chitin, etc.

[0062] Thus, a method for making an electrocompacted leather material may include: applying a solution of dissolved collagen in aqueous buffer onto an electrocompaction surface; compacting the collagen into a dense network with an electrical field; inducing fibrillation of the collagen network; removing water from the collagen network; and incorporating lubricant in the collagen network.

[0063] For example, a method for making an electrocompacted leather material, the method comprising: applying a solution of dissolved collagen in aqueous buffer onto an electrocompaction surface; compacting the collagen into a dense network with an electrical field; inducing fibrillation of the collagen; stabilizing the fibrillar collagen network; removing water from the collagen (including from the entire network and/or displacing water bound to the collagen fibrils); incorporating lubricant in the collagen network; dyeing and applying a surface finish on the collagen network; and drying the collagen network.

[0064] In any of these methods the protein monomers (e.g., collagen monomers) may be polymerized into dimers, trimers and higher order oligomers prior to compaction and fibrillation. The fibrillation may be induced through the addition of salts such as sodium phosphate, potassium phosphate, potassium chloride and sodium chloride. Fibrillation may be induced through a pH shift following the addition of acids or bases such as sodium carbonate, sodium bicarbonate and sodium hydroxide. Fibrillation may be induced through the incorporation of nucleation agents such as collagen microgels, microparticles, nanoparticles, and natural and synthetic microfibers.

[0065] Collagen fibrils may be chemically modified to promote chemical or physical crosslinking between collagen fibrils. Stabilization of the fibrillar collagen network may be accomplished through incorporating molecules with di, tri and multifunctional reactive groups such as chromium, amine, carboxylic acid, sulfate, sulfite, sulfonate, aldehyde, hydrazide, sulfhydryl, diazirine, aryl-azide, acrylate, epoxide, or phenol.

[0066] Any of these electrocompacted leathers may be fixed, e.g. by cross-linking the collagen. For example, the fibrillated collagen may be stabilized through chromium, aldehyde or vegetable tannin based tanning processes known in the leather industry.

[0067] Any of these electrocompacted leathers may also have a reduced water content (e.g., may be dehydrated) compared to native leather. For example, the water content of the fibrillated collagen may be greater than 90% (w/w), which may be reduced to less than 15% (e.g., less than 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc.) of the final leather. Thus, water may be removed from the collagen material through solvent exchanges with solvents such as acetone, ethanol, or diethyl ether. The water may be removed through air or vacuum drying. For example, at least 75%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, etc. of the water may be removed.

[0068] Any of these electrocompacted leathers may include a lubricant (e.g., by fat liquoring to add the lubricant). The lubricant may be any hydrophobic material, such as a lubricating fat and/or oil that may be incorporated into the material.

[0069] Any of these materials may be dyed, retanned, finished and dried through processes known in the leather industry.

[0070] In some variations, an electrocompacted leather material may be fabricated from a matrix of electrocompacted and cross-linked collagen fibrils as described herein and may include any of the 28 types of collagen proteins isolated from animal tissues or variants thereof. For example, collagen produced by expressing recombinant DNA in bacteria, plant, yeast, or mammalian cells may be used as the source collagen. The collagen or collagen-like proteins may be produced through chemical peptide synthesis technologies. In other variations, it is not necessary to form a hydrogel (or may not be accurate to refer to the resulting fibrils of collagen as a “hydrogel”).

[0071] The collagen (e.g., in some cases a matrix of collagen fibrils) may be transformed into a leather-like material by removing water from the material, or in some cases displacing the water from the fibrils of collagen (e.g., using a dewetting agent), and incorporating crosslinking agents, fats, or oils to stabilize the collagen network. The final water content of the material may be between 25 and 10% (e.g., between 15% and 20%, etc.) (w/w).

[0072] The material of the fibril network may be a porous network of collagen or collagen-like fibrils. The fibrils may be between about 1 nm to 1 μm in diameter. The fibrils may be between about 100 nm to 1 mm in length. The fibril network may lack higher order fiber and fiber bundle organization. The fibril density may be between about 5 mg/cc to 500 mg/cc (e.g., between 10 mg/cc to 400 mg/cc, between 20 mg/cc to 300 mg/cc, between 100 mg/cc to 400 mg/cc, or any subrange thereof). The thickness of of the material may be between about 0.05 mm to 10 mm (e.g., between 0.5 mm to 5 mm, greater than 1 mm, etc.); this thickness may be the thickness of the dried material. The elongation at break may be between 0% to 300%. The tensile strength may be between about 1 MPa to 100 MPa. The elastic modulus may be between about 1 kPa to 100 MPa.

[0073] The finished leather-like material may be used in any product where native leather is used, such as a watchstrap, footwear, wallet, jewelry, belt, glove, handbag, briefcase, piece of luggage, upholstery for furniture or transportation, or clothing article.

EXAMPLES

[0074] Commercially available collagen type I was obtained from bovine skin via acetic acid extraction and pepsin digestion was purchased as a 6 mg/ml solution in 0.1 N hydrochloric acid. This stock solution (˜50 ml) was dialyzed against 5 gl of deionized water overnight. Silicone spacers of 1 or 2 mm diameter (in this example, the spacers are spherical, however other shapes and dimensions may be used) were arranged on a stainless steel or graphite plate to enclose a 2.5×5 cm area, open on one side (FIG. 3A). The dialyzed solution was poured into this mold and covered with a second plate, enclosing an approximately 1.25 ml volume between the two plates. The silicone spacers also served as electrical insulators between the plates. A stable, variable voltage source with current limiting capability was supplying the electrical current across the two plates (FIG. 3B), voltage and current was monitored with multimeters connected in parallel and in series to the plates. The electrical parameters were chosen to result in an electric field of 1-25 kV and current density of 0.5-10 A/m2. The duration of the electrocompaction process depended on the voltage applied and plate separation: increasing the electrical field strength was achieved either by increasing the voltage or decreasing the separation between the plates. The closer the plates were, the higher the pH gradient become, providing thus the capability to control layer thickness. The procedure was repeated by removing excess water from the top of the already compacted layer and replacing it with stock collagen solution. Thus, sequential compaction steps controlled the thickness of the final material. The resulting collagen sheets (FIG. 3C) consisted of closely associated, dense, entangled collagen monomers where no D-banding was observed (FIG. 4A) The collagen sheet was then incubated in the presence of PBS for a minimum of 2 hrs. to fibrillate it. The presence of fibers was confirmed by transmission electron microscopy (FIG. 4B), whereas the dense porous fibril network was visualized with scanning electron microscopy (FIG. 5).

[0075] The fibrillated and compacted collagen was dehydrated in a series of acetone solutions (3×1 hr at 25° C.). Following acetone dehydration, the collagen material was incubated in a fat liquor solution containing either 20% (v/v) cod liver oil or 20% (v/v) Lipoderm A1 fatliquor in 80% acetone overnight while shaking at 40 rpm. Following incubation in the fatliquor solution, the material was dried at room temperature overnight. Mechanical analysis confirmed penetration of the cod oil into the material, preventing fibril-fibril sticking during drying (FIG. 6).

Electrospinning

[0076] Although collagen networks have been produced as materials for biomedical applications such as forming implant for use in a body, very little has been done regarding forming collagen materials for use as durable, attractive and wearable fabrics such as leather, which raise a number of very different concerns and issues compared to biomedical materials. For example, when forming collagen structures for biomedical applications, monomers of the collagen triple helix have been extracted from animal tissue, such as bovine dermis, resolubilized in acidic solution and then electrospun. The basic principle of the electrospinning is illustrated in FIGS. 7A-7B. In the initial basic technology, fibers were deposited at a low rate and only in a random manner. Lately several advances have been achieved: the fibers formed by electrospinning can now be deposited according to a defined orientation (FIG. 8A), the density and diameters of fibers can be modified during the process to form multi-layered material (FIG. 8B), and the method may be scaled (see, e.g., http://www.sncfibers.com; and http://arsenalmedical.com/technology/axiocore-drug-delivery-platform).

[0077] For example, twisted, continuous nanofiber yarns may be formed having diameters of ˜100 micrometers. Described herein are methods for forming an engineered leather (e.g., biofabricated leather) using electrospinning, as well an engineered/biofabricated electrospun leathers made using these techniques. The resulting leather may be distinguishable from native leather, but may have the same gross properties, look and feel (texture) of native leather including grossly mimicking the dermis structure (grain and corium) of native leather.

[0078] In general, described herein are electrospun leather materials and methods of making them. For example, a method of forming an electrospun leather material may include: electrospinning a protein solution (e.g., a collagen solution) to form an unwoven (e.g., collagen) network and tanning the electrospun protein.

[0079] For example, a method of forming an electrospun leather material may include: culturing collagen-secreting cells; harvesting collagen from the cells into a collagen solution; forming an unwoven network of collagen by electrospinning the collagen solution; tanning the unwoven electrospun network of collagen.

[0080] In any of these variations, collagen may be used as described herein. Other proteins and particularly fibril or fiber-assembling proteins, may be used additionally or alternatively, such as keratins, chitins, etc.

[0081] In any of these examples, the protein solution (e.g., collagen) solution may be formed by a cell-cultured system, or from an animal or plant source (including cultured extracts from animals or plants that are cultured). For example, any of these methods may include culturing a protein-secreting cells and harvesting collagen from the cells into the collagen solution. Alternatively or additionally, any of these methods may include acquiring collagen from an animal or plant source and forming a collagen solution from the acquired collagen.

[0082] In general, tanning includes cross-liking of the protein that is being electrospun. In particular, tanning includes cross-linking of collagen. Tanning may comprise stabilizing the electrospun network by incorporating one or more of a chromium based, aldehyde based, epoxide based, or sulfo-NHS based crosslinkers into the dissolved collagen solution prior to electrospinning. For example, tanning may include stabilizing the electrospun network using a chromium- or aldehyde-based tanning process. Surprisingly, the cross-linking agent (tanning agent) may be added to the solution before it is electrospun.

[0083] Any of the electrospun leathers described herein may include a lubricant; the lubricant may be added by a fatliquoring process. In some variations, the lubricant (e.g., a hydrophobic material such as an oil or fat) may be added during the electrospinning process or after the network has been formed. For example, any of these methods may include incorporating a lubricant into the unwoven electrospun network of collagen through a fat liquoring processes.

[0084] In general, any of these electrospun leathers may also be dyed and may therefore include a dying step. For example, any of these methods may include dying the unwoven electrospun network of collagen. Similarly, these materials may be finished by applying a finish to the surface of the unwoven electrospun network of collagen. For example, the method may include retanning (e.g., a second tanning/crosslinking step) and finishing the unwoven electrospun network of collagen. Any of these methods may include using the formed material to create a leather product. For example, any of these methods may include forming from the unwoven electrospun network of collagen one or more of a: watchstrap, footwear, wallet, jewelry, belt, glove, handbag, briefcase, piece of luggage, upholstery for furniture or transportation, or clothing article.

Example 2

[0085] FIGS. 9A-9D illustrate one example of an electrospun leather fabricated as described herein. In this example, Type I collagen was isolated from bovine skin by acid/basic style extraction method was frozen and lyophilized. The lyophilized protein was dissolved in acidic solution before being electrospun. The fiber orientation was random as observed by SEM (FIG. 9A). This electrospun network was cross-linked to improve stability. A dehydrothermal cross linker (DHT; FIG. 9B) was used. One noticeable effect was the resistance in aqueous solutions (FIG. 9C). The DHT cross-linked network remained intact while the un-cross-linked material dissolved in water and saline solutions. The formed networks were measured. The characteristics of the fibers that constituted the networks were evaluated by SEM imaging (FIG. 9D).

[0086] The electrospun collagen sheets were incubated in a fat liquor solution containing 20% (v/v) castor oil in 80% ethanol overnight while shaking at 40 rpm. Following incubation in the castor oil solution, the electrospun sheets were dried overnight at 37° C. in a dehydrator. The samples were imaged before, during and after the fat liquoring process was completed (FIG. 10). After drying, the weight and mechanical properties of the material were measured and compared to the ones of the untreated sheets. (Shown in FIGS. 11 and 12A-12D). Weight measurements and mechanical analysis confirmed penetration of the castor oil into the fibrillar collagen network, preventing fibril-fibril sticking during drying (FIGS. 13A-13B).

Example 3

[0087] Type I collagen isolated from bovine skin by acid/basic style extraction method was frozen and lyophilized. The lyophilized protein was dissolved in acidic solution before being electrospun. In this example, the diameter and orientation were controlled to achieve multilayered network with distinctive properties in each layer. The bottom layer was composed of larger bundles of fibers (to mimic the corium) while the top layer was made of smaller fibers in random orientation.

[0088] The electrospun collagen multi-layered network was incubated in a fat liquor solution containing 20% (v/v) castor oil in 80% ethanol overnight while shaking at 40 rpm. Following incubation in the castor oil solution, the electrospun sheets were dried overnight at 37° C. in a dehydrator. The multi-layered networks described herein may have a higher mechanical strength, and/or lower water solubility than the monolayers (even thick monolayers) describe in Example 2, above.

[0089] When a feature or element is herein referred to as being “on” another feature or element, it can be directly on the other feature or element or intervening features and/or elements may also be present. In contrast, when a feature or element is referred to as being “directly on” another feature or element, there are no intervening features or elements present. It will also be understood that, when a feature or element is referred to as being “connected”, “attached” or “coupled” to another feature or element, it can be directly connected, attached or coupled to the other feature or element or intervening features or elements may be present. In contrast, when a feature or element is referred to as being “directly connected”, “directly attached” or “directly coupled” to another feature or element, there are no intervening features or elements present. Although described or shown with respect to one embodiment, the features and elements so described or shown can apply to other embodiments. It will also be appreciated by those of skill in the art that references to a structure or feature that is disposed “adjacent” another feature may have portions that overlap or underlie the adjacent feature.

[0090] Terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. For example, as used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items and may be abbreviated as “/”.

[0091] Spatially relative terms, such as “under”, “below”, “lower”, “over”, “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device in the figures is inverted, elements described as “under” or “beneath” other elements or features would then be oriented “over” the other elements or features. Thus, the exemplary term “under” can encompass both an orientation of over and under. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. Similarly, the terms “upwardly”, “downwardly”, “vertical”, “horizontal” and the like are used herein for the purpose of explanation only unless specifically indicated otherwise.

[0092] Although the terms “first” and “second” may be used herein to describe various features/elements (including steps), these features/elements should not be limited by these terms, unless the context indicates otherwise. These terms may be used to distinguish one feature/element from another feature/element. Thus, a first feature/element discussed below could be termed a second feature/element, and similarly, a second feature/element discussed below could be termed a first feature/element without departing from the teachings of the present invention.

[0093] Throughout this specification and the claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” and “comprising” means various components can be co jointly employed in the methods and articles (e.g., compositions and apparatuses including device and methods). For example, the term “comprising” will be understood to imply the inclusion of any stated elements or steps but not the exclusion of any other elements or steps.

[0094] As used herein in the specification and claims, including as used in the examples and unless otherwise expressly specified, all numbers may be read as if prefaced by the word “about” or “approximately,” even if the term does not expressly appear. The phrase “about” or “approximately” may be used when describing magnitude and/or position to indicate that the value and/or position described is within a reasonable expected range of values and/or positions. For example, a numeric value may have a value that is +/−0.1% of the stated value (or range of values), +/−1% of the stated value (or range of values), +/−2% of the stated value (or range of values), +/−5% of the stated value (or range of values), +/−10% of the stated value (or range of values), etc. Any numerical values given herein should also be understood to include about or approximately that value, unless the context indicates otherwise. For example, if the value “10” is disclosed, then “about 10” is also disclosed. Any numerical range recited herein is intended to include all sub-ranges subsumed therein. It is also understood that when a value is disclosed that “less than or equal to” the value, “greater than or equal to the value” and possible ranges between values are also disclosed, as appropriately understood by the skilled artisan. For example, if the value “X” is disclosed the “less than or equal to X” as well as “greater than or equal to X” (e.g., where X is a numerical value) is also disclosed. It is also understood that the throughout the application, data is provided in a number of different formats, and that this data, represents endpoints and starting points, and ranges for any combination of the data points. For example, if a particular data point “10” and a particular data point “15” are disclosed, it is understood that greater than, greater than or equal to, less than, less than or equal to, and equal to 10 and 15 are considered disclosed as well as between 10 and 15. It is also understood that each unit between two particular units are also disclosed. For example, if 10 and 15 are disclosed, then 11, 12, 13, and 14 are also disclosed.

[0095] Although various illustrative embodiments are described above, any of a number of changes may be made to various embodiments without departing from the scope of the invention as described by the claims. For example, the order in which various described method steps are performed may often be changed in alternative embodiments, and in other alternative embodiments one or more method steps may be skipped altogether. Optional features of various device and system embodiments may be included in some embodiments and not in others. Therefore, the foregoing description is provided primarily for exemplary purposes and should not be interpreted to limit the scope of the invention as it is set forth in the claims.

[0096] The examples and illustrations included herein show, by way of illustration and not of limitation, specific embodiments in which the subject matter may be practiced. As mentioned, other embodiments may be utilized and derived there from, such that structural and logical substitutions and changes may be made without departing from the scope of this disclosure. Such embodiments of the inventive subject matter may be referred to herein individually or collectively by the term “invention” merely for convenience and without intending to voluntarily limit the scope of this application to any single invention or inventive concept, if more than one is, in fact, disclosed. Thus, although specific embodiments have been illustrated and described herein, any arrangement calculated to achieve the same purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all adaptations or variations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, will be apparent to those of skill in the art upon reviewing the above description.