Muscle blocks and injection training devices that include muscle blocks

Abstract

The injection training device can include a muscle block, a surface layer, and an intermediate between the muscle block and the surface layer. The muscle block can include one or more regions that include an array of filler material defined by repeating unit cells. The muscle block can provide sufficient back pressure to activate the injector. The surface layer and / or intermediate layer can provide realistic feeling tissue that the user can pinch during the injection process.

Description

[Technical field] 【0001】 The present disclosure relates to tissue analogs comprising muscle blocks, and injection training devices comprising muscle blocks. [Background technology] 【0002】 A syringe for delivering a drug into tissue can be more effective if the user is familiar with the syringe by using a tissue analog or a training device for the syringe that includes a tissue analog. In addition, having a uniform injection target can improve the reliability and reproducibility of studies and investigations on the function and effectiveness of the syringe. Many currently available tissue analogs and injection training devices have difficulty mimicking the back pressure that superficial tissue, subcutaneous tissue, and muscle tissue provide. Furthermore, some tissue analogs and injection training devices are not configured to receive injections and require a mock or dummy syringe as part of the training process. Differences in the injection process between the training scenario and the actual use scenario can result in ineffective training and can impair the user's familiarity with the syringe. Summary of the Invention 【0003】 An embodiment of the present disclosure relates to a muscle block and an injection training device including the muscle block. In one embodiment, the muscle block includes a plurality of first layers and a plurality of second layers. Each first layer of the plurality of first layers includes an array of fillers defined by a first unit cell that repeats in two dimensions in a plane. Each second layer of the plurality of second layers includes an array of fillers defined by a second unit cell that repeats in two dimensions in a plane. The first unit cells may include a doubly or triply periodic array of fillers. The second unit cells may include a doubly or triply periodic array of fillers. 【0004】 The first unit cell may include a three-fold periodic arrangement of fillers including a gyroid shape. The second unit cell may be identical to the first unit cell. The muscle block may have a general geometric shape including a semi-cylinder. The filler may include polylactic acid, polypropylene, polyethylene terephthalate, acrylonitrile butadiene styrene polymer, acrylic styrene acrylonitrile polymer, poly(methyl methacrylate), polyoxymethylene, polyetherimide, one or more other thermoplastic polymers, or other materials usable in additive printing applications. The Shore hardness of the filler may be about 70A to about 90A. The average density of the muscle block may be about 10% fill to about 25% fill. The first unit cell may be a cubic unit cell and may have a length of about 4 mm (millimeters) to about 12 mm. The muscle block may include a capillary having a minimum diameter of about 2 mm to about 8 mm. 【0005】 In another embodiment, an injection training device includes a muscle block and one or more overlying layers above the muscle block. A region of the muscle block may include an array of filler defined by unit cells that repeat in three dimensions. 【0006】 The one or more overlying layers may be designed to allow a user to simulate pinching the skin. The one or more overlying layers may include an intermediate layer and a surface layer. The intermediate layer may include foam rubber, polyurethane, or sponge. The surface layer may include silicone rubber, ethylene propylene rubber, fluoroelastomer, olefin-based rubber, latex rubber, nitrile rubber, or butyl rubber. The filler may include polylactic acid, polypropylene, polyethylene terephthalate, acrylonitrile butadiene styrene polymer, acrylic styrene acrylonitrile polymer, poly(methyl methacrylate), polyoxymethylene, polyetherimide, one or more other thermoplastic polymers, or other materials usable in additive printing applications, and may have a Shore hardness of about 70 A to about 90 A. The area of ​​the muscle block containing the array of fillers defined by unit cells that repeat in three dimensions may comprise at least 80% of the total volume of the muscle block. 【0007】 In another aspect, an injection training device includes a muscle block, a surface layer, and an intermediate layer between the muscle block and the surface layer. The muscle block may include a material having a Shore hardness of about 70A to about 90A. The surface layer may include silicone rubber, ethylene propylene rubber, fluoroelastomer, olefin rubber, latex rubber, nitrile rubber, or butyl rubber. The muscle block may include a region including an array of filler defined by a first unit cell repeating in three dimensions, the unit cell having a density of at least about 10% fill. 【0008】 The intermediate layer may be in contact with the muscle block and the surface layer, and the intermediate layer may comprise foam rubber, polyurethane or sponge. The combined thickness of the surface layer and the intermediate layer may be equal to or less than the height of the muscle block. The injection training device may further comprise a slot. 【0009】 The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate various examples and, together with the description, serve to explain the principles of the disclosed examples and embodiments. Aspects of the present disclosure may be implemented in conjunction with the embodiments illustrated in the accompanying drawings, which illustrate different aspects of the disclosure, and where appropriate, reference numerals designating like structures, components, materials, and / or elements in different drawings are similarly labeled. It is understood that various combinations of structures, components, and / or elements other than those specifically shown are contemplated and are within the scope of the present disclosure. 【0010】 Moreover, many embodiments are described and illustrated herein. The present disclosure is not limited to any single aspect or embodiment thereof, nor to any combination and / or permutation of such aspects and / or embodiments. Moreover, each of the aspects and / or embodiments of the present disclosure may be used alone or in combination with one or more of the other aspects and / or embodiments of the present disclosure. For the sake of brevity, certain permutations and combinations are not separately described and / or illustrated herein. In particular, any embodiment or implementation described herein as "exemplary" should not necessarily be construed as preferred or advantageous over other embodiments or implementations, but rather is intended to reflect or illustrate that the embodiment is an "exemplary" embodiment. [Brief description of the drawings] 【0011】 [Figure 1A] FIG. 1 is a perspective view of an injection training device according to one or more embodiments. [Figure 1B] FIG. 1B is a front view of the injection training device shown in FIG. 1A. [Figure 1C] FIG. 2 is a side view of the injection training device shown in FIGS. 1A and 1B. [Figure 1D] FIG. 1C is a bottom view of the injection training device shown in FIGS. 1A, 1B, and 1C. [Diagram 2] FIG. 1 illustrates a top view of a fastening strap according to one or more embodiments. [Figure 3A] FIG. 1 is a perspective view of an injection training device according to one or more embodiments. [Figure 3B]FIG. 3B is a front view of the injection training device shown in FIG. 3A. [Figure 3C] FIG. 4 is a side view of the injection training device shown in FIGS. 3A and 3B. [Figure 3D] FIG. 4 is a bottom view of the injection training device shown in FIGS. 3A, 3B, and 3C. [Figure 4A] FIG. 1 illustrates a perspective view of a base plate according to one or more embodiments. [Figure 4B] FIG. 4B is a side view of the base plate shown in FIG. 4A. [Figure 4C] FIG. 4C is a top view of the base plate shown in FIGS. 4A and 4B. [Figure 5A] FIG. 1 is a perspective view of an injection training device according to one or more embodiments. [Figure 5B] FIG. 5B is a front view of the injection training device shown in FIG. 5A. [Figure 5C] FIG. 5C is a side view of the injection training device shown in FIGS. 5A and 5B. [Figure 6A] FIG. 1 illustrates a perspective view of a muscle block in accordance with one or more embodiments. [Figure 6B] FIG. 6B is a front view of the muscle block shown in FIG. 6A. [Figure 6C] FIG. 6C is a side view of the muscle block shown in FIGS. 6A and 6B. [Figure 6D] FIG. 6B is a bottom perspective view of the muscle block shown in FIGS. 6A, 6B, and 6C. [Figure 7A] FIG. 1 illustrates a perspective view of a muscle block unit cell according to one or more embodiments. [Figure 7B] FIG. 7B is a front view of the muscle block unit cell shown in FIG. 7A. [Figure 7C] FIG. 7C is a side view of the muscle block unit cell shown in FIGS. 7A and 7B. [Figure 7D] FIG. 7B is a top view of the muscle block unit cell shown in FIGS. 7A, 7B, and 7C. [Figure 8A] FIG. 2 is a perspective view of a muscle blocking layer according to one or more embodiments. [Figure 8B]FIG. 8B is a front view of the muscle block layer shown in FIG. 8A. [Figure 8C] FIG. 8C is a side view of the muscle block layer shown in FIGS. 8A and 8B. [Figure 8D] FIG. 8B is a top view of the muscle block layer shown in FIGS. 8A, 8B, and 8C. [Figure 9A] FIG. 1 is a perspective view of a region of a muscle block, in accordance with one or more embodiments. [Figure 9B] FIG. 9B is a front view of the muscle block area shown in FIG. 9A. [Figure 9C] FIG. 9C is a side view of the muscle block area shown in FIGS. 9A and 9B. [Figure 9D] FIG. 9B is a top view of the muscle block area shown in FIGS. 9A, 9B, and 9C. [Figure 10A] FIG. 1 is a perspective view of a region of a muscle block, in accordance with one or more embodiments. [Figure 10B] FIG. 10B is a front view of the muscle block area shown in FIG. 10A. [Figure 10C] FIG. 10C is a side view of the muscle block area shown in FIGS. 10A and 10B. [Figure 10D] FIG. 10B is a top view of the muscle block area shown in FIGS. 10A, 10B, and 10C. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 【0012】 Also, many embodiments are described and illustrated herein. The present disclosure is not limited to any single aspect or embodiment thereof, nor to any combination and / or permutation of such aspects and / or embodiments. Each of the aspects and / or embodiments of the present disclosure may be used alone or in combination with one or more of the other aspects and / or embodiments of the present disclosure. For the sake of brevity, many of these combinations and permutations are not described separately herein. 【0013】 In particular, for simplicity and clarity of illustration, certain aspects of the figures show the general structure and / or method of construction of various embodiments. Descriptions and details of well-known features and techniques may be omitted to avoid unnecessarily obscuring other features. Elements in the figures are not necessarily drawn to scale, and dimensions of some features may be exaggerated relative to other elements to improve understanding of illustrative embodiments. 【0014】 Reference will now be made in detail to examples of the present disclosure, which are illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. In the following description, relative terms such as "about," "substantially," and "approximately" are used to indicate a possible variation of ±10% in stated numerical values. 【0015】 As mentioned above, a syringe (e.g., an autoinjector) may be more effective if the user is familiar with the syringe by using a training device for the syringe. Training devices that feel consistent with the target tissue and exhibit similar physical properties to the target tissue are most effective. For example, a training device that is too hard or too soft may result in the user not recognizing the appropriate force required to use the syringe in a real-life usage scenario. 【0016】 Some syringes require the user to forcefully press the syringe against the tissue of the injection recipient (e.g., leg muscles) to activate the syringe and cause it to deliver a load (e.g., a medication or another fluid). A training device for a syringe that does not provide an accurate muscle analogue may not be able to provide sufficient back pressure to activate the syringe when the user applies a force that differs from the optimal or intended force application to activate the syringe. For example, if the user uses the syringe too forcefully, the training device may deform more than intended and may not be able to provide sufficient back pressure to activate the syringe. An effective training device for a syringe should activate the syringe even when the force applied by the user varies from the optimal force application (e.g., the applied force is greater than the force intended to activate the syringe). In addition, an effective injection training device allows the user to simulate pinching tissue (e.g., skin or subcutaneous tissue). 【0017】 Injection training devices are most effective when they allow a user to actually deliver the injectable material (e.g., a medication or other fluid). For injection training devices that allow a user to deliver an injectable material, it is desirable for the injection training device to be available for multiple uses. To that end, some injection training devices may be easily washed or otherwise cleaned to allow for repeated use. In other cases, injection training devices may be configured to collect or otherwise absorb injected medication so that multiple injections can be performed with a single training device. 【0018】 The injection training devices and muscle blocks described herein may meet the criteria of an effective injection training device and / or tissue analog. The injection training devices provide sufficient back pressure to activate the autoinjector even when the force applied by the user differs from the intended force application of the syringe. In addition, the injection training devices allow the user to simulate pinching the skin during the injection process. Furthermore, the injection training devices and muscle blocks include spaces (e.g., channels) that allow the injection fluid to enter and pass through the injection training device. The injection training devices described herein include materials that allow the training device to be efficiently and conveniently flushed and / or cleaned between multiple injections. 【0019】 The injection training device and muscle block may be used in research and studies on syringe effectiveness and design. The injection training device and muscle block of the present disclosure may provide a uniform injection target suitable for the development and evaluation of pre-existing, new, or improved syringes. For example, studies may be conducted to investigate possible sources of human error in the injection process, determine possible inefficiencies in syringe designs, and / or develop new syringe designs. In such studies, it may be beneficial to have a uniform injection target and / or a target that responds consistently to an external force regardless of the direction of the force. The injection training device and muscle block described herein are designed to respond consistently to an external force regardless of the direction of the force, thereby resulting in a more uniform injection target for multiple users. The uniform response from the injection training device reduces existing sources of error and allows for more meaningful and accurate data collection. 【0020】 Examples of syringes that may be used with the embodiments disclosed herein may include those described in U.S. Provisional Application No. 63 / 134554, U.S. Design Application No. 29 / 760798, U.S. Patent No. 10,182,969, U.S. Patent Application Publication No. 2020 / 0086051, U.S. Patent Application Publication No. 2020 / 0306453, WO 2020 / 247686, and WO 2021 / 003409, each of which is incorporated by reference in its entirety. 【0021】 Injection training equipment The injection training device may include a muscle block and one or more layers (e.g., a surface layer, an intermediate layer, a skin-simulating layer, a subcutaneous tissue-simulating layer) above the muscle block. The structure of the muscle block may prevent clogging and / or coring of a syringe (e.g., a needle or other drug delivery component of a syringe). The muscle block is also configured to be permeable to injected fluids and to respond isotopically to an applied external force. With reference to FIGS. 1A-1D, the injection training device 100 may include a muscle block 200, an intermediate layer 120, and a surface layer 130. 【0022】 The injection training device 100 may include an intermediate layer 120 above and in contact with the muscle block 200. For example, an inner surface (e.g., a bottom surface) of the intermediate layer 120 may be in contact with a top surface (e.g., a curved top surface) of the muscle block 200. The injection training device 100 may also include a surface layer 130 positioned above the intermediate layer 120. For example, an inner surface of the surface layer 130 may be in contact with an outer surface of the intermediate layer 120, which is opposite the inner surface of the intermediate layer 120. 【0023】 The intermediate layer 120 may include foam rubber, polyurethane, sponge, or other deformable material. The intermediate layer 120 may be porous, allowing a drug introduced by a syringe to pass through the intermediate layer 120 and reach the muscle block 200. Additionally or alternatively, the injection training device 100 may be configured such that, when delivering a drug, the needle or outlet of the syringe extends through the intermediate layer 120 so that the drug is administered directly to the muscle block 200. The injection training device 100 may function as a training device for subcutaneous and / or dermal injections. When used as a training device for subcutaneous and / or dermal injections, if a user overinserts the syringe (e.g., accidentally pierces and positions the syringe into the muscle block 200), the structure of the muscle block 200 prevents coring and blockage of the syringe and allows the drug to pass through the muscle block 200. 【0024】 The surface layer 130 may comprise an elastomer, such as, for example, silicone rubber, ethylene propylene rubber, fluoroelastomer, olefin-based rubber, latex rubber, nitrile rubber, butyl rubber, or other elastic material. In some embodiments, the surface layer 130 comprises a material that can be pierced by a needle or other outlet of a syringe. The surface layer 130 may be thin enough and / or flexible enough to ensure that a needle or outlet of a syringe can pass from an outer surface of the surface layer 130, through the thickness of the surface layer 130, out an inner surface of the surface layer 130, and into one or more other overlying layers (e.g., intermediate layer 120) and / or muscle block 200. In some embodiments, the surface layer 130 may be hydrophobic or include a hydrophobic coating to aid in cleaning of the surface layer 130 between multiple injections. 【0025】 During operation of the injection training device 100, the surface layer 130 may act as an analog of skin tissue, and the intermediate layer 120 may act as an analog of subcutaneous tissue (e.g., fat and other subcutaneous tissue). The dimensions and elasticity of the intermediate layer 120 and the surface layer 130 may allow a user to simulate pinching the skin during operation of a syringe with the injection training device 100. As previously mentioned, the ability for a user to simulate pinching the skin during the injection training process allows the injection training device 100 to familiarize a user with the injection process in a realistic setting. 【0026】 In some embodiments, the muscle block 200 can have a generally semi-cylindrical shape. In other embodiments, the muscle block 200 can be rectangular, trapezoidal, any shape with a generally flat surface opposite a curved surface, or any other shape that approximates human tissue. Indeed, the muscle block 200 can include one or more curves or other topographies to simulate any of many different injection sites on the human body. The other layers of the injection training device 100 (e.g., the middle layer 120 and the surface layer 130) can conform to the top surface of the muscle block 200. For example, the other layers of the injection training device 100 (e.g., the middle layer 120 and the surface layer 130) can have a preformed curvature that aligns with the curved top surface of the muscle block 200. In some embodiments, the middle layer 120 can be flexible and can conform to the shape of the top surface of the muscle block 200. Additionally or alternatively, the surface layer 130 can be flexible and can conform to the shape of the outer surface of the middle layer 120. 【0027】 The intermediate layer 120 may have a generally rectangular cross-sectional shape. For example, the intermediate layer 120 may have an inner surface (e.g., a surface in contact with the muscle block 200) and an outer surface (e.g., a surface in contact with the surface layer 130). The inner surface may be substantially the same size and shape as the outer surface. The intermediate layer 120 may have a thickness (i.e., the distance between the inner surface and the outer surface) of about 5 mm to about 30 mm, for example, about 5 mm to about 25 mm, about 5 mm to about 20 mm, about 5 mm to about 15 mm, about 10 mm to about 20 mm, about 10 mm to about 15 mm, about 15 mm to about 20 mm, or about 15 mm. The intermediate layer 120 may have a consistent thickness between the inner surface and the outer surface. In some embodiments, the first portion of the intermediate layer 120 has a thickness greater than the second portion of the intermediate layer 120. 【0028】 The intermediate layer 120 may have a length and width sufficient to cover the top surface of the muscle block 200. In some embodiments, the length and / or width of the intermediate layer 120 may be longer or shorter than the length and / or width necessary to cover the top surface of the muscle block 200. 【0029】 In the embodiment shown in FIGS. 1A-1D, the length of the intermediate layer 120 is equal to the length of the muscle block 200. Thus, the entire length of the muscle block 200 is covered by the intermediate layer 120. In some embodiments, the intermediate layer 120 may have a length that is greater than the length of the muscle block 200. In such embodiments, a portion of the intermediate layer 120 extends beyond the anterior and / or posterior surface of the muscle block 200. In some cases, the intermediate layer 120 may have a length that is less than the length of the muscle block 200, in which case a portion of the front of the intermediate layer 120, the rear of the intermediate layer 120, or both at the upper surface of the muscle block 200 is not covered by the intermediate layer 120. 【0030】 1A-1D, the width of intermediate layer 120 is less than the width required to cover the entire top surface of muscle block 200. Thus, a portion of the height of the top surface (e.g., the curved top surface) of muscle block 200 is not covered by intermediate layer 120. Stated differently, a portion of the top surface of muscle block 200 is visible below intermediate layer 120 in the side view of injection training device 100 shown in FIG. 1C. In other embodiments, the width of intermediate layer 120 is sufficient to cover the entire top surface of muscle block 200, such that the top surface of muscle block 200 would not be visible in the side view of injection training device 100. 【0031】 The surface layer 130 may have a generally rectangular cross-sectional shape. For example, the surface layer 130 may have an inner surface (e.g., a surface in contact with the intermediate layer 120) and an outer surface (e.g., an upper surface of the injection training device 100). The inner surface may be substantially the same size and shape as the outer surface. The surface layer 130 may have a thickness (i.e., a distance between the inner surface and the outer surface) of about 1.0 mm to about 3.0 mm, for example, about 1.0 mm to about 2.5 mm, about 1.5 mm to about 2.5 mm, about 1.0 mm to about 2.0 mm, or about 1.5 mm to about 2.0 mm. In some cases, the surface layer 130 may have a thickness of 3.0 mm or less, because a surface layer 130 having a thickness of more than 3.0 mm may prevent the syringe from functioning properly. The surface layer 130 may have a consistent thickness between the inner surface and the outer surface. In some embodiments, the first portion of the surface layer 130 has a thickness that is greater than a thickness of the second portion of the surface layer 130 . 【0032】 The facing layer 130 can have a length and width sufficient to cover the outer surface of the intermediate layer 120. In some embodiments, the length and / or width of the facing layer 130 can be longer or shorter than the length and / or width necessary to cover the outer surface of the intermediate layer 120. 【0033】 In the embodiment shown in FIGS. 1A-1D, the length of the surface layer 130 is equal to the length of the intermediate layer 120. As a result, the entire length of the intermediate layer 120 is covered by the surface layer 130. In some embodiments, the surface layer 130 may have a length that is greater than the length of the intermediate layer 120. In such embodiments, a portion of the surface layer 130 extends beyond the leading edge and / or the trailing edge of the intermediate layer 120. In some cases, the surface layer 130 may have a length that is less than the length of the intermediate layer 120. In such cases, a portion of the outer surface of the intermediate layer 120 in front of the surface layer 130, behind the surface layer 130, or both is not covered by the surface layer 130. 【0034】 1A-1D, the width of surface layer 130 is less than the width required to cover the outer surface of intermediate layer 120. Thus, a portion of the width of intermediate layer 120 is not covered by surface layer 130. Stated differently, a portion of the outer surface of intermediate layer 120 is visible below surface layer 130 in the side view of injection training device 100 shown in FIG. 1C. In other embodiments, the width of surface layer 130 is sufficient to cover the entire width of intermediate layer 120, such that the outer surface of intermediate layer 120 will not be visible in the side view of injection training device 100. 【0035】 As described herein, the intermediate layer 120 and the surface layer 130 may be provided as separate structures that can be separated for cleaning. In some embodiments, the injection training device 100 includes the intermediate layer 120 and the surface layer 130 provided as a unitary structure overlying the muscle block 200. In other embodiments, the injection training device 100 includes a skin layer overlying the muscle block 200, where the skin layer is equivalent in structure and function to the intermediate layer 120 and / or the surface layer 130 described herein. Other combinations of overlying layers that achieve the functions and benefits of the intermediate layer 120 and / or the surface layer 130 may be used in the injection training device 100 with the muscle block 200 described herein. 【0036】 The layers overlying muscle block 200 (eg, middle layer 120 and surface layer 130) may be joined and secured to muscle block 200 with fastening straps, hook-and-loop fasteners, adhesives, or combinations thereof. 【0037】 1A-1D, the injection training device 100 can include a slot 150. The slot 150 may traverse a portion or the entire width of the injection training device 100. For example, the slot 150 may extend from a first side of the muscle block 200 (e.g., where the curved top surface meets a first edge of the flat base) to a second side of the muscle block 200 (e.g., where the curved top surface meets a second edge of the flat base). The slot 150 may also extend through the surface layer 130 and the middle layer 120, as shown in FIGS. 1A-1D. In some embodiments, the width of the middle layer 120 and the surface layer 130 is short enough so that the slot 150 does not extend through the middle layer 120 and the surface layer 130 and does not obstruct the slot 150. In some embodiments (such as those shown in FIGS. 3A-3D and 5A-5C and described in more detail below), the portion of the slot 150 that extends through the surface layer 130 and the intermediate layer 120 has a height that is less than the height of the portion of the slot 150 in the muscle block 200. This height of the portion of the slot 150 in the surface layer 130 and the intermediate layer 120 may be small enough to secure a fastening strap, as described below. 【0038】 1A-1D show a slot 150 extending across the entire width of the injection training device 100 and centrally located along the length of the injection training device 100, but this is by way of example only. The slot 150 may span only a portion of the width of the injection training device 100 and may be located anywhere on the injection training device 100, not just centrally along the length. Additionally or alternatively, the injection training device 100 may include a slot 150 that extends across the entire length or a portion of the length of the injection training device 100. Further, the injection training device 100 may include multiple such slots 150 or other suitable features, as desired. 【0039】 In embodiments in which the injection training device 100 includes a slot 150, the slot 150 may be configured to interact with a base plate and / or fastening straps. For example, the base plate and / or fastening straps may have one or more protrusions or members that engage the slot 150 and hold the injection training device 100 in place relative to the base plate. As shown in FIGS. 1A-1D , the slot 150 may have a rectangular cross-section and a consistent profile throughout the slot 150. In other embodiments, the cross-section of the slot 150 may have another shape that allows it to interact with the base plate and / or fastening straps. The dimensions of the slot 150 may be consistent throughout the slot 150 or may vary (e.g., the slot may be deeper, shallower, wider, or narrower from one end of the slot to the other). 【0040】 The injection training device 100 may include a fastening strap 400. With reference to Figure 2, the fastening strap 400 may include a body 430 and one or more ends 450. The body 430 of the fastening strap 400 may have a length sufficient to extend from one end of the injection training device 100 to an opposite end of the injection training device 100. 【0041】 One or more ends 450 of the fastening straps 400 may have a shape configured to interact (e.g., interlock) with one or more components of the base plate 500 and / or the injection training device 100. For example, the slots 150 through the surface layer 130 and the intermediate layer 120 may have dimensions that allow the ends 450 of the fastening straps 400 to pass through the slots 150. The dimensions of the ends 450 may prevent the fastening straps 400 from easily passing through the slots 150 in both directions after the fastening straps 400 are inserted therethrough, thereby retaining the fastening straps within the injection training device 100. When the fastening straps 400 are retained by the injection training device 100, at least a portion of the body 430 of the fastening straps 400 may be disposed within a portion of the slots 150 within the muscle block 200. 【0042】 For example, as shown in Figures 3A-3D, a first portion (e.g., end 450) of the fastening strap 400 may extend beyond a first exterior surface of the injection training device 100. A second portion (e.g., end 450) of the fastening strap 400 opposite the first portion may extend beyond a second exterior surface of the injection training device 100. As shown in Figures 3A-3D, the first and exterior surfaces may be on opposite sides of the injection training device 100. A third portion (e.g., body 430) of the fastening strap between the first and second portions may be disposed within slot 150. 【0043】 The injection training device 100 may be configured to interact (e.g., interlock) with a base plate 500. The base plate 500 may include a wall surrounding a bottom surface to support and maintain the shape of the injection training device 100. One or more walls of the base plate 500 may include features configured to interact with the fastening strap 400. With reference to FIGS. 4A-4C, in one example, the base plate 500 may include two end walls 510 and two side walls 515. The dimensions of the base plate 500 may be large enough that the injection training device 100 may be retained within the end walls 510 and side walls 515 of the base plate 500. The end walls 510 may have a curvature that matches the curvature of the end of the injection training device 100. The height and width of the end walls 510 may be sufficient to cover the entire end face of the injection training device 100. The height of the sidewalls 515 may be sufficient to cover the edges of the surface layer 130 and the intermediate layer 120 and / or the interface between the overlying layer and the muscle block 200. 【0044】 In some embodiments, the base plate 500 can be foldable. The end walls 510 and side walls 515 can be folded such that the base plate 500 forms a planar shape. When the end walls 510 and side walls 515 extend up at an angle to the bottom of the base plate 500, features on the end walls 510 can engage features from the side walls 515 to reinforce the three-dimensional shape of the base plate 500. 【0045】 In some embodiments, the bottom of the base plate 500 includes a skid resistant region 520. The skid resistant region 520 may be provided as a separate structure on the bottom of the base plate 500 or may be incorporated into the bottom surface of the base plate 500. The skid resistant region 520 may include any material that provides increased sliding friction and / or increased surface tack. The skid resistant region 520 may include any shape along the bottom surface of the base plate 500 that provides increased sliding friction and / or increased surface tack. 【0046】 In some embodiments, the injection training device 100 may interact with a base plate 500 and a fastening strap 400. One or more walls (e.g., side wall 515) of the base plate 500 may include a retaining feature 540. The retaining feature 540 may be configured to receive the fastening strap 400. For example, the width of the body 430 of the fastening strap 400 may be narrow enough to pass through the retaining feature 540, but the width of the end 450 of the fastening strap 400 is too large to pass through the retaining feature 540. In this manner, the retaining feature 540 may help secure the injection training device 100, including the muscle block 200, the overlying layer, and the fastening strap 400, in place relative to the base plate 500. 【0047】 An exemplary injection training device 100 including a fastening strap 400 and a base plate 500 is shown in Figures 5A-5C. In the examples shown in Figures 5A-5C, similar to the embodiment shown in Figures 3A-3D, the surface layer 130 and the intermediate layer 120 may each include a portion of the slot 150 having a lower height than the portion of the slot 150 in the muscle block 200. In these examples, the portion of the slot 150 in the surface layer 130 may be surrounded by the material of the surface layer 130, and the portion of the slot 150 in the intermediate layer 120 may be surrounded by the material of the intermediate layer 120. The fastening strap 400 may pass from a first exterior surface of the injection training device 100, through the slot 150 (including through a first portion of the surface layer 130, through a first portion of the intermediate layer 120, through the muscle block 200, through a second portion of the intermediate layer 120, and through a second portion of the surface layer 130) to a second exterior surface of the injection training device 100. 5A-5C , the position of the retaining feature 540 may be configured to align with the slot 150 when the injection training device 100 is within the base plate 500. Engaging the fastening strap 400 with the retaining feature 540 after the fastening strap has passed through the slot 150 may provide further securement of the injection training device to the base plate 500. Additionally or alternatively, engaging the fastening strap 400 with the retaining feature 540 after the fastening strap has passed through the slot 150 provides further securement of the overlay layer to the muscle block 200. 【0048】 In some embodiments, the base plate 500 may include one or more additional features that allow the base plate 500 to be secured to another surface. For example, after the fastening straps 400 are engaged with the retaining features 540, the base plate 500 may engage an additional strap or securing device that may be attached to a vertical surface, limb, or other tissue during operation of the injection training device 100 to more accurately simulate an injection in a real use scenario. 【0049】 Muscle block As described above, the injection training device 100 includes a muscle block 200. The muscle block 200 may simulate the backpressure that muscle tissue provides when an injection device (e.g., an autoinjector, a wearable injection device, a prefilled syringe, etc.) is pushed into tissue (e.g., to activate the injection device). The muscle block 200 may be configured such that the backpressure provided by the muscle block 200 may be consistent regardless of the direction of the injection. Additionally, the muscle block 200 may allow fluid to pass through the muscle block. For example, a drug or other fluid delivered during an injection may pass through tubules, pores, or other microstructures within the muscle block 200. Similarly, during cleaning of the injection training device 100, water or other cleaning fluid may pass through the microstructures of the muscle block 200, allowing for effective and efficient cleaning. 【0050】 2A-2D, the general geometric shape of muscle block 200 may include a half cylinder, another shape having a flat surface opposite a curved surface, or another shape that approximates human tissue. Although these descriptions describe the general geometric shape of muscle block 200, the materials that make up muscle block 200 may be arranged in a detailed pattern of filler 225 and spaces 250. In this context, spaces 250 refer to the portions of muscle block 200 between filler 225, which may include, for example, air. Filler 225 may include one or more flexible or semi-rigid polymers. For example, the filler material 225 may include polylactic acid, polypropylene, polyethylene terephthalate, acrylonitrile butadiene styrene polymer, acrylic styrene acrylonitrile polymer, poly(methyl methacrylate), polyoxymethylene, polyetherimide, thermoplastic urethane, thermoplastic elastomer, flexible photopolymer resin (e.g., including acrylate monomers, urethane dimethacrylate, and / or isobornyl acrylate), other thermoplastic polymers, or other materials usable in additive printing applications. 【0051】 The filler 225 may have a Shore hardness, as measured by ASTM D2240, of about 40A to about 90A, e.g., about 50A to about 90A, about 60A to about 90A, about 70A to about 90A, about 75A to about 90A, about 70A to about 85A, about 75A to about 85A, about 80A to about 85A, or about 80A. 【0052】 2A-2D, in embodiments in which the muscle block 200 approximates a portion of a limb (e.g., a leg), the muscle block 200 may have a length L of about 80 millimeters (mm) to about 150 mm, e.g., about 90 mm to about 140 mm, about 100 mm to about 130 mm, about 110 mm to about 120 mm, about 80 mm to about 115 mm, about 115 mm to about 150 mm, greater than about 75 mm, less than about 160 mm, or about 115 mm, etc. The muscle block 200 may have a width W of about 65 mm to about 105 mm, e.g., about 70 mm to about 95 mm, about 75 mm to about 90 mm, about 78 mm to about 85 mm, about 65 mm to about 85 mm, about 80 mm to about 105 mm, greater than about 60 mm, less than about 110 mm, or about 82 mm, etc. The muscle block 200 may have a height H (e.g., the maximum distance between the top surface and the base of the muscle block 200) of about 20 mm to about 70 mm, e.g., about 25 mm to about 60 mm, about 30 mm to about 55 mm, about 35 mm to about 45 mm, about 20 mm to about 45 mm, about 45 mm to about 70 mm, greater than about 15 mm, less than about 75 mm, or about 45 mm. 【0053】 The dimensions of the muscle block 200 may vary based on the intended use. For example, the ranges given are for uses in which the muscle block 200 acts as an analog for a portion of a lower leg. In other embodiments, the general geometry, shape, and dimensions of the muscle block 200 may be altered to act as a more accurate analog for other tissues and regions of tissue. For example, a smaller muscle block 200 may be provided to act as an analog for a portion of an arm limb. A larger muscle block 200 may be provided as an analog for an entire limb or other region of tissue. 【0054】 The particular pattern of filler 225 and spaces 250 within muscle block 200 can form tubules, pores, channels, grooves, or other microstructures that allow fluid to pass through the muscle block. Depending on the pattern of filler 225 and spaces 250, the microstructures may have linear features and consistent dimensions. In other embodiments, the walls of the microstructures are curved, and the width or diameter of these features widens or narrows along the path of the microstructure. In one example, the microstructures of muscle block 200 can include channels or tubules having a minimum width of about 2 mm to about 6 mm, such as about 4 mm. 【0055】 2A-2D, the arrangement of fillers 225 and spaces 250 that make up muscle block 200 forms a repeating pattern. The arrangement of fillers 225 and spaces 250 may be defined by one or more unit cells (e.g., a cubic unit cell). For example, a unit cell may be the smallest repeating unit of a portion (e.g., a layer or region) of muscle block 200. A unit cell includes a three-dimensional arrangement of repeatable fillers 225 and spaces 250. 【0056】 The surface of a unit cell defining a portion of the muscle block 200 may be doubly periodic or triply periodic. In the case of triply periodic unit cells, the dimensions of the unit cell may be cubic (e.g., the length, width, and height of the unit cell are equal). The length of such a cubic unit cell may be about 4 mm to about 16 mm, e.g., about 16 mm or less, about 12 mm or less, about 10 mm or less, about 8 mm or less, about 4 mm to about 12 mm, about 4 mm to about 8 mm, about 6 mm to about 10 mm, or about 8 mm, etc. In the case of doubly periodic unit cells, the dimensions of the unit cell may be cubic (e.g., the length, width, and height of the unit cell are equal) or the dimensions of the unit cell may be rectangular (e.g., the length is equal to the width but not the height). The length of such a rectangular unit cell may be about 4 mm to about 16 mm, for example, about 16 mm or less, about 12 mm or less, about 10 mm or less, about 8 mm or less, about 4 mm to about 12 mm, about 4 mm to about 8 mm, about 6 mm to about 10 mm, or about 8 mm, and the height of such a rectangular unit cell may be about 4 mm to about 16 mm, for example, about 16 mm or less, about 12 mm or less, about 10 mm or less, about 8 mm or less, about 4 mm to about 12 mm, about 4 mm to about 8 mm, about 6 mm to about 10 mm, or about 8 mm. 【0057】 The arrangement of the fillers 225 and spaces 250 constituting the muscle block 200 shown in Figures 2A-2D is defined by a unit cell including a triplicate periodic surface. Specifically, in the embodiment shown in Figures 2A-2D, the arrangement of the fillers 225 and spaces 250 constituting the muscle block 200 is defined by a gyroid shape that repeats in three dimensions. 【0058】 During the manufacture of the muscle block 200, the infill 225 is formed in the shape of a periodic surface, and other infills 225, also in the shape of a periodic surface, are added to the formed infill 225. By repeating the pattern defined by this unit cell in two or three dimensions, as described herein, a muscle block 200 having the advantageous properties described above may be formed. For example, the repeating shape (e.g., gyroid shape) of the infill 225 may contribute to the isotropic response to externally applied forces exhibited by the muscle block 200. Additionally, the repeating pattern (e.g., gyroid shape) of the infill 225 and spaces 250 may allow fluid to pass through the muscle block 200. 【0059】 A portion of the muscle block 200 may have an arrangement of infill material 225 and spaces 250 defined by a repeating arrangement of the infill material 225 and spaces 250 in two dimensions, e.g., a pattern of infill material 225 and spaces 250 defined by unit cells may repeat along the length and width of the muscle block 200, along the length and height of the muscle block 200, or along the width and height of the muscle block 200 to form a layer (e.g., a vertical layer or a horizontal layer) of the muscle block 200. Additionally or alternatively, a portion of the muscle block 200 may have an arrangement of infill material 225 and spaces 250 defined by a repeating arrangement of the infill material 225 and spaces 250 in three dimensions, e.g., a pattern of infill material 225 and spaces 250 defined by unit cells may repeat along the length, height, and width of the muscle block 200. 【0060】 In the embodiment shown in Figures 2A-2D, the arrangement of fillers 225 and spaces 250 that make up the muscle block 200 is defined by unit cells 220 shown in Figures 3A-3D and is repeated in three dimensions. With reference to Figures 3A-3D, the fillers 225 in the unit cells 220 are triplicate periodic and repeat in three dimensions, namely, length, width, and height. The shape of the fillers 225 shown in the unit cells 220 is called a gyroid, and when repeated in three dimensions, it forms several tubules within the muscle block 200. For example, the spaces 250 shown in Figures 3B-3D are within the tubules formed by the gyroid fill. In the example shown in Figures 2A-2D, the axes of the unit cells are aligned with the length, width, and height of the general geometry of the muscle block 200. This is one example shown for clarity. In other embodiments, the unit cells may be skewed, yawed, tilted, pitched, and / or rolled relative to the edges and surfaces of the general geometric shape of the muscle block 200. 【0061】 3A-3D includes a gyroid-shaped arrangement of fillers 225 and spaces 250, but this is by way of example only. A muscle block 200, or a portion of a muscle block 200, may be defined by a unit cell 220 that includes any doubly or triply periodic arrangement of fillers 225 and spaces 250, such as, for example, a linoloid shape, a catenoid shape, a helicoid shape, or other Schwartz surface. 【0062】 As alluded to above, the arrangement of fillers 225 and spaces 250 defined by the unit cells 220 may be repeated in two or three dimensions. FIGS. 4A-4D show the unit cells 220 of FIGS. 3A-3D repeated in two dimensions, lengthwise and widthwise, in the same plane to form a layer 240 of the muscle block 200. The layers 240 may be combined to form the entire muscle block 200, or a region of the muscle block 200. For example, horizontal layers 240 may be stacked on top of each other, or vertical layers 240 may be stacked next to each other to form a three-dimensional region of the muscle block 200. When the layers 240 are combined to form a region of the muscle block 200, the arrangement of fillers 225 and spaces 250 within the layer 240 may be defined by the same unit cells 220 or by different unit cells 220. For example, the tubules, channels, or other microstructures of a first layer 240 may align with the microstructures of a second layer 240 even if the adjacent layers 240 are defined by different unit cells 220. 【0063】 5A-5D show the unit cells 220 of FIGS. 3A-3D repeated in three dimensions, length, width, and height, to form regions 330 of the muscle block 200. Regions 300 of the muscle block 200 defined by repeating unit cells 220 may be stacked adjacent to and / or on top of each other to form the muscle block 200. Regions 330 or layers 240 defined by unit cells 220 repeating in three or two dimensions may be positioned adjacent to regions 330 or layers 240 defined by the same unit cell 220 or different unit cells 220. For example, tubules, channels, or other microstructures of a first layer 240 or region 330 may be aligned with microstructures of a second layer 240 or region 330, even when adjacent layers 240 or regions 330 are defined by different unit cells 220. 【0064】 Near the periphery of the muscle block 200, around the layers 240 defined by the repeating unit cells 220, and / or around the areas defined by the unit cells 220, the repeating structure can be modified to accommodate the general geometry of the muscle block 200 or to join the microstructure of a first area or layer 240 with the microstructure of a second area or layer 240. The total volume of the muscle block 200 occupied by the areas 330 defined by the repeating unit cells 220 or layers 240 can represent at least about 20% of the total volume of the muscle block 200. For example, the volume of the muscle block 200 occupied by the region or layer 240 defined by one or more repeating unit cells 220 can represent at least about 40%, at least about 60%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 99%, between about 50% and about 100%, between about 75% and about 100%, between about 85% and about 100%, or between about 85% and 99% of the total volume of the muscle block 200. In calculating the percentage of the muscle block 200 defined by the repeating unit cells, the volume occupied by the slots 150 is not taken into account relative to the total volume of the muscle block 200. 【0065】 As mentioned above, the arrangement of the filler 225 and spaces 250 in the muscle block 200 may be designed to approximate the back pressure provided by muscle tissue. In addition to changing the arrangement of the filler 225 as defined by the periodic shapes in the unit cell 220, the percentage of filling by those shapes may also be adjusted. For example, for a given periodic shape, several different densities of that shape may be defined within the unit cell. The density of the filler 225 in the region 330 of the muscle block may be calculated as a filling fraction, where the volume of the filler 225 in a given region (e.g., in the unit cell 220) is taken as a percentage of the total volume of the given region. The filler 225 and spaces 250 in the region 330 of the muscle block 200 shown in Figures 5A-5D are arranged according to a unit cell 220 with a gyroid shape and a filling fraction of 20%. The filling fraction can be increased by adding more filler 225 in place of spaces 250 according to the periodic shapes. Similarly, the filling factor can be decreased by removing filler material to increase the space 250 according to the periodic shape. Figures 6A-6D show a region 335 of a muscle block 200 defined by unit cells 220 that contain a gyroid shape but have a filling factor of 10%. The decreased filling factor results in more space 250 and less filler material 225 within the region 335 of the muscle block 200. 【0066】 The fill factor may be adjusted based on the properties of the tissue that is being approximated by the muscle block 200. For example, stiffer, more elastic tissue may be approximated by an increased fill factor. Additionally, if the composition of the filler 225 is adjusted to result in a filler 225 having altered stiffness, flexibility, or other properties that affect the backpressure provided by the muscle block 200, the fill factor may be adjusted such that the muscle block 200 provides the required backpressure and exhibits the required flexibility. 【0067】 The average density of muscle block 200 (e.g., the average filling rate of an area of ​​muscle block 200 defined by one or more repeating unit cells) may be a filling rate of about 5% to about 50%, for example, a filling rate of about 5% to about 40%, a filling rate of about 5% to about 25%, a filling rate of about 5% to about 20%, a filling rate of about 5% to about 15%, a filling rate of about 10% to about 25%, a filling rate of about 10% to about 20%, or a filling rate of about 15%, etc. 【0068】 In some embodiments, a first region of the muscle block 200 may have a different filling factor than a second region of the muscle block 200 to generate a particular force profile of the muscle block 200. Additionally, or alternatively, each region of the muscle block 200 defined by a repeating unit cell has the same filling factor. 【0069】 The present disclosure is further illustrated by the following non-limiting sections. Item 1 a plurality of first layers, each first layer of the plurality of first layers including an array of filler material defined by a first unit cell that repeats in two dimensions in a plane; a plurality of second layers, each second layer of the plurality of second layers including an array of filler material defined by a second unit cell that repeats two-dimensionally in a plane; the first unit cell includes a doubly periodic or triply periodic array of fillers; The second unit cell is a muscle block, comprising a doubly periodic or triply periodic array of filler material. 【0070】 Item 2 2. The muscle block of item 1, wherein the first unit cell comprises a triplicate periodic array of fillers comprising a gyroid shape. 【0071】 Item 3 3. The muscle block of item 2, wherein the second unit cell is identical to the first unit cell. Item 4 2. The muscle block of item 1, wherein the muscle block has a general geometric shape that includes a half cylinder. 【0072】 Item 5 2. The muscle block of claim 1, wherein the filler material comprises polylactic acid, polypropylene, polyethylene terephthalate, acrylonitrile butadiene styrene polymer, acrylic styrene acrylonitrile polymer, poly(methyl methacrylate), polyoxymethylene, polyetherimide, one or more other thermoplastic polymers, or other materials usable in additive printing applications. 【0073】 Item 6 2. The muscle block according to item 1, wherein the Shore hardness of the filler is about 70A to about 90A. Item 7 2. The muscle block according to item 1, wherein the average density of the muscle block is from about 10% to about 25%. 【0074】 Item 8 2. The muscle block according to item 1, wherein the first unit cell is a cubic unit cell and has a length of about 4 mm to about 12 mm. 【0075】 Item 9 2. The muscle block according to item 1, wherein the muscle block comprises a capillary having a minimum diameter of about 2 mm to about 8 mm. 【0076】 Item 10 Muscle block and and one or more overlying layers above the muscle block, An injection training device in which the muscle block region comprises an array of filler defined by unit cells that repeat in three dimensions. 【0077】 Item 11 11. The injection training device of item 10, wherein the one or more overlying layers are designed to allow the user to simulate pinching the skin. 【0078】 Item 12 11. The injection training device according to item 10, wherein the one or more overlying layers include an intermediate layer and a surface layer. 【0079】 Item 13 13. The injection training device of item 12, wherein the intermediate layer comprises foam rubber, polyurethane, or sponge. 【0080】 Item 14 Item 13. The injection training device according to item 12, wherein the surface layer comprises silicone rubber, ethylene propylene rubber, fluoroelastomer, olefin-based rubber, latex rubber, nitrile rubber, or butyl rubber. 【0081】 Item 15 Item 11. The injection training device of item 10, wherein the filler material comprises polylactic acid, polypropylene, polyethylene terephthalate, acrylonitrile butadiene styrene polymer, acrylic styrene acrylonitrile polymer, poly(methyl methacrylate), polyoxymethylene, polyetherimide, one or more other thermoplastic polymers, or other materials usable in additive printing applications and has a Shore hardness of about 70 A to about 90 A. 【0082】 Item 16 11. The injection training device of item 10, wherein the area of ​​the muscle block comprises at least 80% of the total volume of the muscle block. 【0083】 Item 17 A muscle block including a material having a Shore hardness of about 70A to about 90A; a surface layer including silicone rubber, ethylene propylene rubber, fluoroelastomer, olefin-based rubber, latex rubber, nitrile rubber, or butyl rubber; an intermediate layer between the muscle block and the superficial layer; An injection training device, wherein the muscle block includes a region including an array of filler defined by a first unit cell that repeats in three dimensions, the unit cell having a density of at least about 10% fill factor. 【0084】 Item 18 18. An injection training device according to item 17, wherein the intermediate layer is in contact with the muscle block and the superficial layer, the intermediate layer comprising foam rubber, polyurethane, or sponge. 【0085】 Item 19 18. An injection training device according to item 17, wherein the combined thickness of the surface layer and the intermediate layer is equal to or less than the height of the muscle block. 【0086】 Item 20 Item 18. The injection training device of item 17, further comprising a slot configured to interact with the base plate. 【0087】 Those skilled in the art will appreciate that the conception on which this disclosure is based may be readily used as a basis for designing other devices and systems for carrying out some of the purposes of the present disclosure, and therefore the scope of the appended claims should not be deemed to be limited by the foregoing description.

Claims

[Claim 1] A muscle block, a plurality of first layers, each first layer of the plurality of first layers including an array of filler material defined by a first unit cell that repeats in two dimensions in a plane; a plurality of second layers, each second layer of the plurality of second layers including an array of filler material defined by a second unit cell that repeats in two dimensions in a plane; the first unit cell includes a doubly or triplicate periodic array of fillers; A muscle block, wherein the second unit cell includes a doubly periodic array or a triplicate periodic array of filler material. [Claim 2] 10. The muscle block of claim 1, wherein the first unit cell comprises a triplicate periodic array of fillers comprising a gyroid shape. [Claim 3] The muscle block of claim 2 , wherein the second unit cell is identical to the first unit cell. [Claim 4] 10. The muscle block of claim 1, wherein the muscle block has a general geometric shape that includes a half cylinder. [Claim 5] 10. The muscle block of claim 1, wherein the filler material comprises polylactic acid, polypropylene, polyethylene terephthalate, acrylonitrile butadiene styrene polymer, acrylic styrene acrylonitrile polymer, poly(methyl methacrylate), polyoxymethylene, polyetherimide, one or more other thermoplastic polymers, or other materials usable in additive printing applications. [Claim 6] 2. The muscle block of claim 1, wherein the Shore hardness of the filler material is from about 70A to about 90A. [Claim 7] 2. The muscle block of claim 1, wherein the average density of the muscle block is between about 10% and about 25%. [Claim 8] 2. The muscle block of claim 1, wherein the first unit cell is a cubic unit cell and has a length of about 4 mm to about 12 mm. [Claim 9] 2. The muscle block of claim 1, wherein the muscle block comprises a capillary having a minimum diameter of about 2 mm to about 8 mm. [Claim 10] An injection training device comprising: Muscle block and and one or more overlying layers over the muscle block, An injection training device, wherein the muscle block region comprises an array of filler material defined by unit cells that repeat in three dimensions. [Claim 11] 11. The injection training device of claim 10, wherein the one or more overlying layers are designed to allow a user to simulate pinching the skin. [Claim 12] 11. The injection training device of claim 10, wherein the one or more overlying layers include an intermediate layer and a surface layer. [Claim 13] 13. An injection training device according to claim 12, wherein the intermediate layer comprises foam rubber, polyurethane, or sponge. [Claim 14] 13. The injection training device of claim 12, wherein the surface layer comprises silicone rubber, ethylene propylene rubber, fluoroelastomer, olefin-based rubber, latex rubber, nitrile rubber, or butyl rubber. [Claim 15] 11. The injection training device of claim 10, wherein the filler material comprises polylactic acid, polypropylene, polyethylene terephthalate, acrylonitrile butadiene styrene polymer, acrylic styrene acrylonitrile polymer, poly(methyl methacrylate), polyoxymethylene, polyetherimide, one or more other thermoplastic polymers, or other materials usable in additive printing applications, and has a Shore hardness of about 70A to about 90A. [Claim 16] 11. An injection training device according to claim 10, wherein the region of the muscle block comprises at least 80% of the total volume of the muscle block. [Claim 17] An injection training device comprising: a muscle block comprising a material having a Shore hardness of about 70A to about 90A; a surface layer including silicone rubber, ethylene propylene rubber, fluoroelastomer, olefin-based rubber, latex rubber, nitrile rubber, or butyl rubber; an intermediate layer between the muscle block and the surface layer; An injection training device, wherein the muscle block includes a region including an array of filler defined by a first unit cell repeating in three dimensions, the unit cell having a density of at least about 10% fill factor. [Claim 18] 18. An injection training device according to claim 17, wherein the intermediate layer is in contact with the muscle block and the surface layer, the intermediate layer comprising foam rubber, polyurethane, or sponge. [Claim 19] 18. An injection training device according to claim 17, wherein the combined thickness of said surface layer and said intermediate layer is equal to or less than the height of said muscle block. [Claim 20] 18. An injection training device according to claim 17, further comprising a slot configured to interact with the base plate.

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