Tissue mimicking materials

Abstract

Aspect and embodiments relate to a tissue mimicking material, a clinical phantom including a tissue mimicking material and a method of manufacture of a tissue mimicking material. One aspect provides a tissue mimicking material comprising: an elastomeric solid foam. The foam comprises gas pockets dispersed in an elastomeric material matrix and a liquid lubricant arranged within the gas pockets of the elastomeric solid foam. Aspects and embodiments recognise that a self lubricating tissue mimicking material provides a mechanism to emulate particular in vivo mammalian tissues. The modified foam material in accordance with aspects has various physical properties and characteristics which can be tuned or refined to simulate the characteristics of a mammalian tissue which the foam is intended to mimic.

Description

[0001] TISSUE MIMICKING MATERIALS

[0002] FIELD OF THE INVENTION

[0003] Various example embodiments relate to a tissue mimicking material, a clinical phantom including a tissue mimicking material and a method of manufacture of a tissue mimicking material.

[0004] BACKGROUND

[0005] Tissue mimicking materials can provide a mechanism for a clinician to practice use of surgical or other interventional techniques. Assessment of the outcome of such techniques can be made before using the techniques on in vivo tissue of a subject needing treatment.

[0006] In order for a tissue mimicking material to be useful to a clinician, the material should respond to surgical or other interventional techniques in a manner similar to that of the tissue being simulated by the tissue mimicking material.

[0007] It is difficult to reproduce the response of some in vivo tissues with known tissue mimicking materials.

[0008] SUMMARY

[0009] The scope of protection sought for various example embodiments of the invention is set out in the independent claims. The example embodiments and features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the invention.

[0010] According to one, but not necessarily all, aspect there is provided a tissue mimicking material comprising: an elastomeric solid foam, the foam comprising gas pockets dispersed in an elastomeric material matrix; and a liquid lubricant arranged within the gas pockets of the elastomeric solid foam.

[0011] Aspects recognise that in vivo mammalian tissue takes various forms. Some tissues are spongiform, and / or have interstices which contain bodily fluid(s). Aspects seek to accurately and reliably reproduce main physical characteristics of such in vivo tissues to provide a realistic mechanism for a clinician to practice use of surgical or other interventional techniques. Aspects recognise that provision of an elastomeric foam can mimic the texture and feel of substantially spongiform mammalian tissue, and that provision of a liquid lubricant within the interstices or gas pockets within the elastomeric foam can allow for realistic reproduction of the tissue in vivo, when it is likely to be subject to being surrounded, or filled, with one or more type of bodily fluid, for example, blood, urine, lymphatic fluid, mucous secretions and similar. One aspect comprises a tissue mimicking material which may comprise: an elastomeric solid foam. That is to say, interstices or pockets of gas are formed within a solid elastomeric material matrix. Elastomeric material can be used to more accurately mimic the deformable nature of many mammalian tissues. The foam may comprise gas pockets dispersed in an elastomeric material matrix. By creating a foam having appropriately sized pockets and / or an appropriate pocket to solid material ratio in any dimension, a bulk physical characteristic, for example, density or deformability, of a tissue of interest can be reproduced. The tissue mimicking material may comprise a liquid lubricant arranged within the gas pockets of the elastomeric solid foam. In some cases, the lubricant may be integrated into the elastomeric matrix, within the gas pockets, or in both. The liquid lubricant may comprise a fluid. The liquid lubricant may be selected to have physical properties such as, for example, viscosity, which are similar to the bodily fluid which is being mimicked. Viscosity is a measure of the liquid lubricant’s dynamic resistance to a change in shape or to movement of its elements with respect to each other. Centipoise (cP) is a unit of measurement for a liquid's dynamic viscosity, or its resistance to flow when an external force is applied. A fluid with a low cP will flow easily and quickly, while a fluid with a higher cP will flow more slowly. The SI unit for viscosity is the pascal-second (Pa-s), which is equivalent to newton-second per square meter. 1 Pas = 1000cP. It will be appreciated that viscosity of a liquid is dependent upon temperature of the liquid. The higher the temperature T, the lower the viscosity of the liquid. Similarly, it will be appreciated that viscosity of a liquid is dependent upon pressure of the liquid. The higher the pressure, the higher the viscosity of the liquid. Where reference is made to viscosity herein, it is assumed to be a viscosity measurement made at substantially room temperature, or substantially body temperature, and the pressure is assumed to be approximately atmospheric pressure.

[0012] In some embodiments, the foam comprises an open cell foam. An open cell foam has pockets which are connected to one or more other pocket. In an open cell foam, liquid or fluid within the pockets can flow or move between pockets. In some embodiments, the foam comprises a closed cell foam. A closed cell foam has pockets which are isolated from other pockets in the foam. In other words, pockets in a closed cell foam are not connected. In a closed cell foam, liquid or fluid within each pocket is not able to flow or move to another pocket.

[0013] Tissue-Mimicking Materials (TMM) can be used to replicate physical properties of tissues in bench tests, providing a homogeneous practical alternative to tissue samples. Tissues which can be mimicked using the described tissue mimicking material include, for example, in general, soft tissue and connective tissue. More particularly, tissue mimicking materials can mimic cancerous soft tissue growths, adipose tissue, breast tissue, skin tissue, muscle tissue, and connective tissue. Some of the physical properties of such mammalian tissues which can be replicated by a lubricated foam tissue mimicking material include material density, foam structure, hardness / softness and deformability.

[0014] In relation to the mimicking of erectile tissue, for example, mapping the following physical characteristics in the tissue mimicking material can result in a realistic erectile tissue mimicking material: In some embodiments, the tissue mimicking material has a density in the range 0.35 to 0.60 g / cm3. In some embodiments, the tissue mimicking material has a density in the range 0.40 to 0.50 g / cm3. In some embodiments, the tissue mimicking material has a density in the range 0.45 to 0.50 g / cm3. In some embodiments, the tissue mimicking material has a density in the range 0.46 to 0.48 g / cm3. In some embodiments, the tissue mimicking material has a density of around 0.47 g / cm3.

[0015] In some embodiments, the gas pockets have a diameter between 150 pm and 3000 pm. In some embodiments, the gas pockets have a diameter between 160 pm and 2700 pm. In some embodiments, the gas pockets have an average diameter between 300 pm and 450 pm. In some embodiments, the gas pockets have an average diameter between 300 pm and 450 pm. In some embodiments, the gas pockets have an average diameter between 350 pm and 400 pm. In some embodiments, the gas pockets have an average diameter of around 375 pm.

[0016] In some embodiments, the elastomeric solid foam material has a Shore Hardness in a range between 12.0 and 13.5. In other words, the unmodified elastomeric solid foam material, excluding inclusion of a liquid lubricant, may have a Shore Hardness in a range between 12.0 and 13.5. In some embodiments, the elastomeric material comprises a plastic or rubber foam. Examples include: polyurethane foam, silicone rubber foam, polystyrene foam, PVC foam, and latex foam.

[0017] In some embodiments, the elastomeric material comprises silicone. In some embodiments, the elastomeric material comprises a cured silicone foam. In some embodiments, the silicone foam is UV and / or water resistant. In some embodiments, the silicone foam is heat resistant up to 175 degrees Centigrade. In some embodiments, the silicone foam is resistant to oxidation and / or ozone degradation. In some embodiments, the elastomeric matrix comprises Soma Foama™’ a soft curable two-component silicone flexible foam. In some embodiments, the elastomeric matrix comprises Soma Foama™ 15. In some embodiments, the elastomeric matrix comprises Soma Foama™ 25.

[0018] In some embodiments, the elastomeric material may comprise a polyurethane, and the foam may comprise a polyurethane foam. In some embodiments, the foam may comprise a curable polyurethane foam. In some embodiments, the elastomeric material may comprise polyethylene, and the foam may comprise a polyethylene foam. In some embodiments, the foam may comprise a curable polyethylene foam.

[0019] In order to accurately mimic mammalian tissue, the liquid lubricant provided in the gas pockets or interstices in the foam may be arranged to fill the pockets to a greater or lesser degree. That is to say, not all pockets may contain liquid lubricant in some embodiments. Similarly, in some embodiments, those pockets which do contain liquid lubricant may be substantially filled with liquid lubricant. In some embodiments, substantially all closed pockets may be substantially filled with liquid lubricant. In some embodiments, the liquid lubricant fills at least a portion of the gas pockets of the elastomeric foam. In some embodiments, the liquid lubricant partially fills at least a portion of the gas pockets of the elastomeric foam. In some embodiments, the liquid lubricant coats an inner surface of at least a portion of the gas pockets of the elastomeric foam.

[0020] In some embodiments, the liquid lubricant comprises a water-based lubricant. Accordingly, such lubricants may be selected to emulate bodily fluids such as blood, urine, or similar. In some embodiments, the water based liquid lubricant has a viscosity at room temperature in the range 2000cP to 3000cP. In some embodiments, the water based liquid lubricant has a lubricity indicated by the coefficient of friction between two steel plates in the range 0.1 to 0.2.

[0021] In some embodiments, the liquid lubricant comprises liquid soap.

[0022] In some embodiments, the liquid lubricant comprises an oil based lubricant. Accordingly, such lubricants may be selected to emulate bodily fluids such as lymphatic fluid, mucous secretions or similar. In some embodiments, the oil-based liquid lubricant has a viscosity at room temperature in the range 20cP to 70cP. In some embodiments, the oil based liquid lubricant has a lubricity indicated by a coefficient of friction between two steel plates in the range 0.05 to 0.10.

[0023] In some embodiments, the tissue mimicking material comprises an erectile tissue mimicking material. In some embodiments, the tissue mimicking material comprises a bone marrow mimicking material. In some embodiments, the tissue mimicking material comprises an alveolar lung tissue mimicking material. In some embodiments, the tissue mimicking material comprises a cancerous soft tissue growth mimicking material. In some embodiments, the tissue mimicking material comprises an adipose tissue mimicking material. In some embodiments, the tissue mimicking material comprises one of: breast tissue mimicking material or skin tissue mimicking material or muscle tissue mimicking material or connective tissue mimicking material.

[0024] According to one, but not necessarily all, aspect there is provided a surgical phantom comprising a tissue mimicking material as described above.

[0025] In some embodiments, the phantom comprises a urogenital surgical phantom, or a skeletal surgical phantom.

[0026] In some embodiments, the phantom comprises a penile surgical phantom.

[0027] According to one, but not necessarily all, aspect there is provided a method of manufacturing a tissue mimicking material, the method comprising: forming an elastomeric solid foam, the foam comprising gas pockets dispersed in an elastomeric material matrix; and providing a liquid lubricant within the gas pockets of the elastomeric solid foam. According to some embodiments, forming an elastomeric solid foam comprises: providing a curable elastomeric compound.

[0028] According to some embodiments, forming an elastomeric solid foam comprises introducing gas into a liquid curable elastomeric compound.

[0029] According to some embodiments, forming an elastomeric solid foam comprises applying a high pressure gas to a liquid curable elastomeric compound.

[0030] According to some embodiments, the method comprises providing a curable elastomeric solid foam by mixing a powder volume of a powdered silicon formulation with a liquid volume of water to form a curable silicon compound.

[0031] According to some embodiments, the ratio of powder volume to liquid volume is 1 :1. Accordingly, the physical characteristics of a resulting elastomeric foam may be adjustable based on a powder volume to liquid volume. A stiffer, more rigid, closer foam may result from a higher powder volume to liquid volume ratio. A softer, more deformable, larger celled foam may result from a lower powder volume to liquid volume ratio.

[0032] According to some embodiments, the method comprises providing a curable elastomeric solid foam by combining two liquid components: a base (Part A) and a curing agent (Part B). According to some embodiments, the ratio of base to curing agent is 1:1.

[0033] According to some embodiments, the method comprises allowing the compound to cure.

[0034] According to some embodiments, providing a liquid lubricant within the gas pockets of the elastomeric solid foam comprises: introducing the liquid lubricant into the elastomeric solid foam.

[0035] According to some embodiments, providing a liquid lubricant within the gas pockets of the elastomeric solid foam comprises: mixing the liquid lubricant into the curable elastomeric compound. In some embodiments, the method comprises providing a curable elastomeric solid foam by mixing a lubricant volume of lubricant liquid with a powder volume of a powdered silicon formulation and a liquid volume of water to form a curable silicon compound. According to some embodiments, the ratio of lubricant volume to powder volume to liquid volume is 1 :1 :1. According to some embodiments, the ratio of lubricant volume to powder volume to liquid volume is 2:3:3. According to some embodiments, the ratio of lubricant volume to powder volume to liquid volume is 2:1:1.

[0036] According to some embodiments, the method comprises providing a curable elastomeric solid foam by combining two liquid components: a base (Part A) and a curing agent (Part B). According to some embodiments, the ratio of base to curing agent is 1:1. According to some embodiments the lubricant may be introduced into the elastomeric solid foam by mixing it with the combined two liquid components. In some embodiments, the lubricant comprises an oil-based liquid lubricant. According to some embodiments, the ratio of lubricant volume to base volume to curing agent volume is 1:5:5. Typically an oil based lubricant and two liquid component elastomeric matrix arrangement involves a lower lubricant proportion compared to water-based alternatives.

[0037] In some embodiments, the foam comprises an open cell foam.

[0038] In some embodiments, the foam comprises a closed cell foam.

[0039] In some embodiments, the tissue mimicking material has a density in the range 0.35 to 0.60 g / cm3.

[0040] In some embodiments, the gas pockets have a diameter between 150 pm and 3000 pm.

[0041] In some embodiments, the gas pockets have a diameter between 160 pm and 2700 pm.

[0042] In some embodiments, the gas pockets have an average diameter between 300 pm and 450 pm.

[0043] In some embodiments, the elastomeric solid foam material has a Shore Hardness in a range between 12.0 and 13.5.

[0044] In some embodiments, the elastomeric material comprises silicone. In some embodiments, the liquid lubricant fills at least a portion of the gas pockets of the elastomeric foam.

[0045] In some embodiments, the liquid lubricant partially fills at least a portion of the gas pockets of the elastomeric foam.

[0046] In some embodiments, the liquid lubricant coats an inner surface of at least a portion of the gas pockets of the elastomeric foam.

[0047] In some embodiments, the liquid lubricant comprises a water based lubricant.

[0048] In some embodiments, the liquid lubricant has a viscosity at room temperature in the range 2000cP to 3000cP.

[0049] In some embodiments, the liquid lubricant has a lubricity coefficient of friction in the range 0.1 to 0.2.

[0050] In some embodiments, the liquid lubricant comprises liquid soap.

[0051] In some embodiments, the liquid lubricant comprises an oil based lubricant.

[0052] In some embodiments, the liquid lubricant has a viscosity at room temperature in the range 20cP to 70cP.

[0053] In some embodiments, the liquid lubricant has a lubricity coefficient of friction in the range 0.05 to 0.10.

[0054] In some embodiments, the tissue mimicking material comprises an erectile tissue mimicking material, or a bone marrow mimicking material, or an alveolar lung tissue mimicking material,

[0055] Further particular and preferred aspects are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with features of the independent claims as appropriate, and in combinations other than those explicitly set out in the claims. Where an apparatus feature is described as being operable to provide a function, it will be appreciated that this includes an apparatus feature which provides that function or which is adapted or configured to provide that function.

[0056] BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Embodiments of the present invention will now be described further, with reference to the accompanying drawings, in which:

[0058] FIG. 1 illustrates schematically a cube of tissue mimicking material according to an arrangement;

[0059] FIG. 2A to FIG. 20 are representations of a mammalian bone surgical phantom including a tissue mimicking material according to an arrangement;

[0060] FIG. 3 is an illustrative digital model of some anatomical structures identified by segmentation and subsequent refinement to create a template model for use in a surgical simulator according to an arrangement;

[0061] FIG. 4 illustrates a surgical simulator at various stages of manufacture;

[0062] FIG. 4A is a cross section of the corpora cavernosa featuring a double layer structure; FIG. 4B is an assembled corporal body;

[0063] FIG. 4C shows six assembled urogenital surgical phantoms incorporating a tissue mimicking material according to arrangements;

[0064] FIG. 5 shows photographs of a urogenital simulator such as that shown in FIG. 4 in use; and

[0065] FIG. 6 is a graphical representation of feedback gathered from a trial of a urogenital simulator such as that shown in FIG. 4.

[0066] DESCRIPTION OF THE EMBODIMENTS

[0067] Before describing particular uses of a tissue mimicking material in accordance with some aspects in more detail, a general overview of an arrangement of a tissue mimicking material is provided.

[0068] FIG. 1 illustrates schematically a cube of tissue mimicking material according to an arrangement. FIG. 1 shows a tissue mimicking material 1 comprising: an elastomeric solid foam 2. The foam 2 comprises gas pockets 3 dispersed in an elastomeric material matrix 4. The tissue mimicking material 1 includes a liquid lubricant 5 arranged within the gas pockets of the elastomeric solid foam. In the arrangement illustrated, the pockets or interstices 3 within the elastomeric material matrix 4 are discrete and largely not interconnected. In other words, the tissue mimicking material arrangement shown in FIG. 1 comprises a closed cell foam. In order for a tissue mimicking material to offer a realistic experience for training, various physical characteristics of the tissue mimicking material shown schematically in FIG. 1 may be matched to a tissue to be emulated. Accordingly the parameters of various aspects of the tissue mimicking material can be adjusted in order to match a resulting physical characteristic of the tissue mimicking material to a tissue which is being emulated. Various physical characteristics and aspects of the tissue mimicking material are now described in detail. It will be appreciated that one or more aspect of the tissue mimicking material can be adjusted in order to match a physical characteristic of the tissue mimicking material to a tissue to be emulated.

[0069] It will be appreciated that a tissue mimicking material such as that shown schematically in FIG. 1 can be formed to have a density which matches a tissue of interest. Density adjustment may occur by adjustment of gas pocket size, gas pocket distribution within the matrix 4, selection of elastomeric material and / or selection of liquid lubricant.

[0070] In relation to a tissue mimicking material emulating erectile tissue, it has been found that a density of tissue mimicking material 1 in the range 0.35 to 0.60 g / cm3is beneficial. A tissue mimicking material for emulation of erectile tissue, formed from Soma FoamaTM25 powder made into a self-lubricating tissue mimicking foam using an equal volume of powder, water and liquid has been found to have a density ranging from 0.46 to 0.48 gem-3, and an average density of 0.47 gem-3

[0071] For such an erectile tissue mimicking material, an analysis foam gas pocket size was undertaken. The following data were obtained from five different images of a cross section of material formed from Soma FoamaTM25 powder made into a self-lubricating tissue mimicking foam using an equal volume of powder, water and liquid lubricant. Each image represented a 2 cm by 2 cm cross-sectional area of the material. The data obtained relates to capturing a diameter of gas pockets 4 within the foam. In other words, the data tracks the size of “the bubbles in the foam”. The measured diameters are summarized in Table 1 set out below:

[0072] TABLE 1

[0073] Mammalian tissues have various levels of deformability, resilience and hardness. For example, bone marrow may have a different texture and resilience to erectile tissue. In relation to erectile tissue formed from Soma FoamaTM25 powder made into a selflubricating tissue mimicking foam using an equal volume of powder, water and liquid, it was found that whilst the elastomeric solid foam material (formed from a 1:1 mix of powder and water) has a Shore Hardness on the 00 scale in a range between 12.0 and 13.5, the hardness of the modified foam material is below the detectable range of the durometer scale, which is calibrated to Shore Hardness 00. This scale is designed for measuring the hardness of very soft materials. Consequently, no measurable hardness readings could be obtained for the modified foam. In contrast, only the premodified Soma Foama 25 foam provided a valid hardness reading. Empirical tests indicated that the physical shape of the modified foam degrades significantly when the soap ratio reaches 50%. The empirical data obtained is summarized in Table 2 below:

[0074] It will be appreciated that a durometer or Shore durometer is a standardized way to measure the hardness of materials like rubber (elastomers) and plastics. The Shore 00 Hardness Scale measures rubbers and gels that are very soft. The Shore A Hardness Scale measures the hardness of flexible moulded rubbers that range in hardness from very soft and flexible, to medium and somewhat flexible, to hard with almost no flexibility at all. Semi-rigid plastics can also be measured on the high end of the Shore A Scale. The Shore D Hardness Scale measures the hardness of hard rubbers, semirigid plastics and hard plastics. The SI unit for hardness is N / mm2, but the Shore Hardness test uses a scale that ranges from 0 to 100. The Shore Hardness test measures the hardness of a material by pressing a “foot” into the material. Depending on the durometer scale being used to measure a material, a different presser foot might be used. For Shore A, a flatter presser foot is used and for a Shore D (harder materials), a more pointed presser foot is used. A Shore Durometer has a meter from 0-100 that it uses to record a reading. Typically a material sample is positioned under the durometer foot. The durometer foot is pressed against the material. A higher result represents a higher resistance to indentation and therefore a higher number on the scale of hardness. There is not a direct relationship between a Shore scale and a Young’s modulus of a material. Nonetheless, calculations exist and will be apparent to the person skilled in the art, which can provide an approximate Young’s modulus of a material based on a Shore scale durometer reading for a given Shore scale.

[0075] TABLE 2

[0076] Tissue mimicking materials such as that shown generally in FIG. 1 can be formed from various elastomeric foam materials. For the purposes of providing a stable tissue mimicking material which does not interact or react with other materials used to create a surgical phantom, it can be useful if the elastomeric material is largely temperature stable and chemically inert. In some arrangements the elastomeric material comprises silicone. In a particular arrangement the tissue mimicking material can be formulated using a foaming silicone, for example, Soma Foama™ mixed with an appropriate liquid lubricant or softener. Soma Foama™ is a soft, two-component platinum silicone flexible foam. The liquid lubricant can be selected such that it does not significantly chemically interact with, or degrade the structure of, the elastomeric material matrix.

[0077] Spongiform tissues of interest for emulation in relation to the tissue mimicking material shown in FIG. 1 typically contain some bodily fluid. Depending upon the tissue of interest, that bodily fluid may comprise blood, urine, lymphatic fluid, mucous or similar. In tissues of interest the bodily fluid may fill the spongiform tissue to varying degrees. Accordingly, some arrangements may provide a tissue mimicking material in which the liquid lubricant fills at least a portion of the gas pockets of the elastomeric foam. In some implementations, the liquid lubricant partially fills at least a portion of the gas pockets of the elastomeric foam. In other implementations, the liquid lubricant coats an inner surface of at least a portion of the gas pockets of the elastomeric foam.

[0078] In an erectile tissue mimicking material formed from Soma Foama TM 25 powder made into a self-lubricating tissue mimicking foam using an equal volume of powder, water and liquid, during the quick curing process, the lubricant (liquid soap) fills a portion of the gas pockets in the foam. These gas pockets eventually form spherical silicone bubbles within the material, which are filled with the lubricant. The outer surface of the moulded material (which is open cell) releases the lubricant in response to applied force. When the material is cut, the inner bubbles (closed cell) break and release the lubricant (liquid soap), enhancing the cutting sensation. This self-lubricating property is particularly beneficial for the creation of surgical phantoms and can result in particularly realistic response of a tissue mimicking material to interventional techniques.

[0079] Depending upon the bodily fluid which may form part of an in vivo tissue being emulated by a tissue mimicking material such as that shown in FIG. 1, differing liquid lubricants may be selected for use in the manufacturing process. Such liquid lubricants may comprise water-based lubricants such as liquid soap, or oil-based lubricants. The liquid lubricant may be selected to have a particular viscosity at room or body temperature, and / or to provide a particular lubricity or coefficient of friction in relation to the selected elastomeric matrix. The lubricity of a liquid offers a measure of the liquid’s ability to reduce friction.

[0080] As described generally above and in more detail below, a tissue mimicking material such as that shown in FIG. 1 may comprise an erectile tissue mimicking material. The general material shown in FIG. 1 is suited to mimicking a corporal cavernosum, making it excellent for practicing a dilation procedure involved in penile implant surgeries. The dilation of the erectile tissue of the cavernosum can be accurately simulated. The liquid lubricant enhances the sensation to a clinician during surgical training, providing a more realistic experience compared to other phantom or phantom-mimicking materials.

[0081] As described generally above and in more detail below, a tissue mimicking material such as that shown in FIG. 1 may comprise a bone marrow mimicking material.

[0082] FIG. 2A to FIG. 2C are representations of a mammalian bone surgical phantom including a tissue mimicking material according to an arrangement. FIG. 2A shows the exterior of a hollow bone phantom in which tissue mimicking material according to an arrangement has been cured. FIG. 2B and FIG. 2C are cross sections of a bone phantom such as that shown in FIG. 2A in which a tissue mimicking material has been formed. A tissue mimicking material described generally in relation to FIG. 1 can be manufactured to be highly effective fin relation to creation of a bone marrow phantom. The bone marrow mimicking material of such an arrangement offers a superior level of mimicry compared to other available phantoms or phantom-mimicking materials. This makes it invaluable for surgical training and other medical applications where realistic simulation of human tissue is crucial. The self-lubricating bone marrow phantom shown in FIGS 2A to 2C includes a tissue mimicking material including an oil-based liquid lubricant. The bone marrow tissue mimicking material is formed from a material manufactured using Soma Foama TM 25 powder made into a self-lubricating tissue mimicking foam using an equal volume of powder, water and oil based liquid lubricant. The phantom releases the oil based liquid lubricant in response to applied force, mimicking the behaviour of stem cells or maturing blood cells within the marrow. Due to the oil-based lubricant, it has been experimentally proven that the lubricating properties can be maintained for an extended period, nearly indefinitely. These unique qualities are unparalleled by any other tissue mimicking material. Arrangements described provide a method of manufacturing a tissue mimicking material such as that shown in FIG. 1. One method of forming such a tissue mimicking material comprises steps including: forming an elastomeric solid foam, the foam comprising gas pockets dispersed in an elastomeric material matrix; and providing a liquid lubricant within the gas pockets of the elastomeric solid foam. Forming the elastomeric solid foam can comprise: providing a curable elastomeric compound. That compound can be provided by mixing a powder volume of powdered silicon formulation with a liquid volume of water to form a curable silicon compound. The method typically comprises molding the curable compound by placing it in a cast or mold in a liquid form and allowing the compound to cure to take a solid form. As part of the manufacturing process, a liquid lubricant can be provided within the gas pockets of the elastomeric solid foam by introducing the liquid lubricant into the elastomeric solid foam. That may occur by mixing the liquid lubricant into the curable elastomeric compound while it is in a liquid form. As described generally above and in more detail below, various experimental tissue mimicking materials have been formed by manufacturing an elastomeric material matrix using Soma Foama™ mixed with a liquid lubricant or softener whilst the Soma Foama™ was in a liquid phase, and then curing the liquid mixture to form a solid matrix. Soma Foama™ is a soft, two-component platinum silicone flexible foam.

[0083] Having described tissue mimicking materials according to arrangements generally above, a possible specific application of a tissue mimicking material in accordance with described arrangements is described in detail. What follows is a detailed implementation of use of a tissue mimicking material to mimic internal erectile tissue of a corpora cavernosa.

[0084] By way of background, to explain why mimicking erectile tissue may be of use, it is useful to understand the clinical situation surrounding erectile dysfunction. Erectile dysfunction (ED) is defined as the consistent or recurrent inability to attain and maintain penile erection sufficient for sexual satisfaction [7], A recent prospective real-world evidence study conducted in the United Kingdom revealed that nearly 50% of adult men are affected by ED [5], Furthermore, projections suggest that by the year 2025, the prevalence of ED will impact approximately 322 million men globally [6], In cases of end-stage ED, penile prostheses (implants) may be deployed. Such penile implants have further applications in treatment of, for example, other medical conditions such as acute ischaemic priapism and / or Peyronie's disease when associated with ED. Penile implant (PI) surgery can be aimed at rectifying erectile dysfunction. Penile surgery is inherently intricate. Such intricacy is particularly apparent in relation to surgical and interventional procedures involving advanced penile prostheses. The nature of penile surgery serves to emphasize that it is important for clinicians to undergo comprehensive training.

[0085] The conventional approach to teaching PI surgery has traditionally adhered to a 'see one, do one, teach one' model [2], However, a paradigm shift is occurring as surgical simulators gain in popularity. The attraction of surgical simulators is driven by ethical advantages and cost efficiency compared to utilization of cadavers.

[0086] In the UK, simulation training for a clinician or surgeon typically involves utilization of anthropomorphic dummies and / or virtual reality (VR) simulators.

[0087] Anthropomorphic dummies typically deployed to simulate penile surgery, including penile implant surgery, primarily comprise a penis formed as a substantially rigid solid plastic body. A typical penile dummy has a unibody design of penis and scrotum and lacks detailed internal anatomical structures other than inclusion of a urethra. Such an absence of functional representation hinders effective simulation of realistic penile tissue response to invasive procedures, such as surgery.

[0088] VR penile surgery simulators provide a user with a 3D display of surgical procedures but do not provide haptic feedback allowing a user to experience realistic textures as might be experienced during human tissue dissection.

[0089] A tissue mimicking material in accordance with described arrangements may support provision of an anatomically accurate penile phantom. Such a penile phantom, which supports practice of implant procedures, can enable a surgeon to practice and improve penis surgery skills. In some implementations, an anatomically accurate phantom may allow a clinician to study a specific patient's anatomy prior to performing a procedure.

[0090] Provision of an anatomically accurate simulator can be achieved through additive manufacturing (AM), which has seen increased usage in healthcare, especially for the development of surgical simulators. AM can provide, as a result of a range of versatile materials, simulators which are cost-effective, widely available, and rapidly produced. AM is considered to represent a suitable technology for the development of surgical simulators. The requirements for a high-fidelity penis simulator for implant surgery are challenging. These requirements include: realistic representation of male urogenital anatomy; simulation of main procedures of implant surgery (corporotomy; dilation; measurement; scrotal pump placement; reservoir placement; and implantation); and error detection (corporal crossover; incorrect prostheses assembly).

[0091] The various stages involved in creation of a high-fidelity penis simulator which includes a tissue mimicking material according to described arrangements are set out in more detail below.

[0092] Imaging Segmentation

[0093] Image segmentation of male urogenital anatomical structures was performed on a series of Digital Imaging and Communication in Medicine (DICOM) formatted images obtained from an anonymized set of pre-operative male patient urogenital contrast MRI and CT scans.

[0094] Both manual and semi-automatic segmentation features of ITK-SNAP (University of Pennsylvania, Philadelphia, PA, USA) were used to process the subject's DICOM images. Segmentation software allowed for accurate segmentation of the male urogenital anatomy, which was used to create a digital 3D model.

[0095] An original segmentation of the testis and epididymis, corpus spongiosum and glans, corpora cavernosa and pelvic bone was obtained.

[0096] To ensure that any resulting surgical simulator based upon the segmentation could be adapted to manufacture appropriate penile prostheses and in order to provide a simulator in which an organ of interest had features of a realistic size and shape for simulation training, 3D meshes of soft tissue structures of the segmentation were refined using a smoothing brush in Meshmixer (Autodesk, USA).

[0097] Additionally, the form of the soft tissue structures was adjusted in consultation with urologists and a penile prostheses developer industry partner to ensure the simulator was effective for training and education purposes.

[0098] To better evaluate and improve the 3D digital anatomies identified in the segmentation, physical 3D printed prototypes of the segmented anatomical structures were created using a polylactic acid (PLA) filament material. Digital models of each component created by the segmentation, smoothing and consultation stages, were sliced using Ultimaker Cura 4.8.0 (Ultimaker, Utrecht, The Netherlands) and 3D printed by using a Chiron FDM 3D printer (Anycubic, Shenzhen, China). The printed physical component models served as a visual representation of the underlying digital model during the consultation process with urology experts, allowing them to evaluate and assess the accuracy of the model more directly.

[0099] In the context of penile implant surgery, the model was further adjusted in size and shape to ensure that it offered an organ having likely compatibility as a candidate for use with penile prostheses. This adjustment was implemented by taking precise measurements of prostheses provided by an industry partner and using those measurements to adjust the corporal bodies of the digital model. The goal was to accurately represent the average size and shape of corporal bodies of a typical male.

[0100] FIG. 3 is an illustrative digital model of some anatomical structures identified by segmentation and subsequent refinement to create a template model for use in a surgical simulator according to an arrangement.

[0101] Mold Making

[0102] Once a size and shape of relevant anatomical structures to be included in a surgical simulator was finalised, a model of each structure was individually exported in STL format from Meshmixer. The exported model was edited in Fusion360 (Autodesk, San Rafael, CA, USA). Utilizing Fusion360, a mold for each structure was created.

[0103] The mold creation process was repeated for all relevant anatomical structures forming part of the simulator, including: corpora cavernosa, corpus spongiosum, glans, a penisscrotum exterior surface, testis & epididymis. In the particular surgical simulator described here in detail, a bespoke design was developed for representation of a penis-scrotum exterior. The bespoke design included an additional hanging portion, designed to recreate a hollow structure typical of a scrotum.

[0104] Exported computer-designed molds were sliced using Cura and 3D printed in PLA using a Chiron FDM 3D printer. Simulator Assembly

[0105] Typical manufacturing processes for a multi-component object follow a principle of starting from an innermost structure and move outwards to creation of outer structures, containing, encapsulating or housing those innermost structures. Such a manufacturing approach was adopted in relation to creation of a penis and scrotum.

[0106] In order to create a realistic model, able to provide appropriate haptic feedback to a user, appropriate tissue mimicking materials were selected for each component of the surgical simulator. By way of example, a material selected for creation of a pelvic bone will typically be substantially inelastic and relatively rigid, whereas a material selected to mimic skin may be flexible, elastic and deformable.

[0107] Based on selection of an appropriate tissue mimicking material, molds of components of the surgical simulator were filled with liquid silicone material. During a curing process, the liquid silicone material undergoes a chemical reaction which causes it to cross-link and form a solid, durable material. The cure time of different silicone materials varies. By way of example, silicon foam takes approximately 15 minutes, and silicon rubber takes, on average, 3 to 4 hours.

[0108] Further details regarding manufacture of various components of the surgical simulator are described below:

[0109] FIG. 4 illustrates a surgical simulator at various stages of manufacture. FIG. 4A is a cross section of the corpora cavernosa featuring a double layer structure. FIG. 4B is an assembled corporal body and FIG. 4C shows six assembled urogenital surgical phantoms incorporating a tissue mimicking material according to arrangements.

[0110] The pelvic bone of the described surgical simulator was 3D printed from a material having appropriate bone-like physical characteristics in order to provide a realistic outcome. Whilst 3-D printing of a full-size pelvic bone is time-consuming, with a duration of approximately 20 hours, it results in a highly accurate representation for use in a surgical simulator. It will be appreciated that a pelvic bone may also be created using a mold and an appropriate moldable material selected to have bone-like physical characteristics after molding.

[0111] Internal erectile tissue of a corpora cavernosa was, in relation to the described surgical simulator, manufactured using a tissue mimicking material in accordance with arrangements described previously. In this surgical simulator, the corpora cavernosa was manufactured from a self-lubricating sponge material. In particular, manufacture of the corpora cavernosa was performed by introducing liquid soap into Soma Foama 25 during the liquid phase of molding, thus transforming it, after curing, into a selflubricating sponge material. During the silicon curing phase of Soma Foama, minuscule interstices are generated within the material. The incorporation of surfactants present in liquid soap, commonly comprising compounds such as sodium lauryl sulfate or sodium laureth sulfate, in the Soma Foama material have a surprising result. Inclusion of the liquid soap in the curable liquid silicon does not detrimentally impact the creation of a silicon foam. The surfactants in the liquid soap demonstrate an affinity for interstitial spaces created within the silicon matrix. As a result, during cutting or dilation processes performed on the resulting material, the surfactants proficiently infiltrate and fill the voids, leading to emergence of a self-lubricating property. That self-lubricating property helps the foam material to effectively mimic particular tissues in a mammalian body, for example: lung tissue, liver tissue, kidney tissue and, as here, erectile tissue of the corpora cavernosa.

[0112] An external layer of the corpora cavernosa can be created by applying a highly flexible and resilient silicon material coating.

[0113] A corpus spongiosum and glans were manufactured using standard Soma Foama 25. The corpus spongiosum and glans were connected to two corpora cavernosa using silicon adhesive. The corpus spongiosum and glans and corpora cavernosa together formed an underlying structure to a penis body.

[0114] Facia was made of Ecoflex Gel 2 that was specifically formulated for pouring and curing on a flat surface.

[0115] Three wires were glued onto the facia layer, on the side of the corpora cavernosa, as an indication of main arteries and veins in the penis region.

[0116] An assembly comprising the the penis body base, the fascia layer, and the wires, was placed in the penis-scrotum exterior mold.

[0117] To form an internal structure of a scrotum, two testes and two epididymis were manufactured using materials selected to have appropriately matched physical characteristics to the component which they are mimicking, in this case, EcoflexOOlO and Ecoflex0030. The resulting testes and epididymis were connected using silicon glue. Fishing wire of 3mm diameter was attached to the tail of the epididymis, to provide an indication of a spermatic cord. A facia layer made of Ecoflex Gel 2 in a manner similar to that set out above was wrapped around the entire assembly of scrotal internal structure. The internal structure of the scrotum is placed in a scrotum room, created by a hanging portion formed as part of the penis-scrotum exterior mold.

[0118] The penis-scrotum exterior mold is shaped to represent skin of a penis and scrotum. A two-stage skin manufacturing technology was utilized to recreate a differentiation of material properties between penis and scrotum skin. Such a differentiation can be achieved by initially pouring DragonSkin FX into the mold around the assembly to form the exterior penis skin.

[0119] Upon complete curing, DragonSkin FX, formulated with Slacker, was utilized to fill the remaining space within the mold, resulting in a connected penis and scrotum with different material properties.

[0120] The resulting penile simulator offers a high level of anatomical accuracy and practicality for corporotomy, dilation procedures and penile prosthesis placement in penile implant surgery. Compared to typical penile simulators, a simulator manufactured as described above can offer several advantages. Firstly, the use of silicone material offers several benefits over PVA gel: silicone is more durable, flexible, and can maintain its shape and properties over time, making it a more reliable biomimetic material. Secondly, use of DICOM imaging to create a model results in a more precise reconstruction of male urogenital anatomy compared to typical simulators. Thirdly, the double-layered structure of the manufactured corpora cavernosa can accurately replicate the structure and strength of a real cavernosa, enabling it to emulate tissue response during dilation procedures while maintaining correct penile anatomy. Fourthly, use of a self-lubricating sponge tissue mimicking material in accordance with arrangements inside the cavernosa reduces resistance to cutting during dilation procedures and replicates the feeling of real dilation. Furthermore, the two-stage skin manufacturing approach results in more realistic replication of human skin by allowing a penis and scrotum to have different material properties whilst also being smoothly connected. Finally, the simulator utilizes cost-effective materials, significantly reducing manufacturing costs without compromising effectiveness. The production cost of a single simulator is around £10. Overall, the male urogenital surgical simulator described above is has potential to significantly improve surgical training. It may have particular application in relation to improvement of penile implant surgical training. However, to provide a more realistic and appropriate penile implant simulator, a human body portion of a simulator, to which the urogenital portion can be attached or connected, can be considered, allowing simulation of reservoir placement in relation to inflatable penile implant surgery.

[0121] To evaluate the efficacy of the male urogenital simulator described above, a quantitative trial was conducted at the Weston Education Centre, King's College Hospital, involving 15 urology trainees and surgeons spanning training stages 3 to 6.

[0122] Six urogenital simulators were specifically manufactured for the trial. The evaluation commenced with a demonstration of penile implant surgery from a skilled surgeon. The surgeon presented the demonstration and delivered a comprehensive lecture on a primary procedure, also elucidating error detection methodologies. Following the demonstration, trainees participated in personalized practice sessions, with an average of three trainees per simulator, under the guidance of experienced surgeons.

[0123] The personalised practice sessions involved practice of procedures including: corporotomy, dilation, measurement, penile prosthesis placement, and scrotal pump placement.

[0124] FIG. 5 shows photographs of a urogenital simulator such as that shown in FIG. 4 in use. In particular FIG. 5 shows the urogenital simulator as utilized in a urology training session at King’s College Hospital, demonstrating progressive steps typical in penile implant (PI) surgery procedures, including: corporotomy, dilation, measurement, and scrotal pump placement.

[0125] After the practical exercise, all participants completed a questionnaire encompassing 19 questions, evaluating dimensions of learning, overall satisfaction, and anatomical accuracy, rated on a Likert scale. Recorded data, treated as numerical variables, were stratified based on the quantity of surgeries conducted (0-250 and 250-1000) and the training stage (stage 3&4, and stage 5&6). The Mann-Whitney II test was utilized to examine noteworthy differences between the specified data groups. This nonparametric test was applied to Likert scale data, which did not follow a normal distribution. The test employed a two-tailed approach with a significance level (a) set at 0.05. FIG. 6 is a graphical representation of feedback gathered from a trial of a urogenital simulator such as that shown in FIG. 4. FIG. 6 presents percentage outcomes of satisfaction across three distinct categories. FIG 6 comprises pie charts showing the qualitative results based on the feedback collected from the surgeons who completed the questionnaire. Left: addressing the learning and overall satisfaction of the surgeon. Middle: the accuracy and quality of the model. Right: overall satisfaction. The outcomes are notably affirmative, with 96% of responses concurring that the simulator serves as a valuable and proficient training instrument for urology trainees, fostering enhanced confidence post-session. Respondents also acknowledge the simulator's efficacy in facilitating male urogenital anatomy study and the practice of corporotomy, dilation, and inflatable penile implant replacement procedures. There is a unanimous absence of dissatisfaction within the learning category. In terms of anatomical accuracy, 86% of responses indicate satisfaction, particularly concerning sensory and visual realism, with a singular dissatisfied response pertaining to the representation of the penis and scrotum skin. Within the overall satisfaction category, 89% of feedback expresses contentment with the simulator holistically. Furthermore, all trainees and surgeons express a desire to incorporate such a simulator into a training program.

[0126] Feedback was also categorized based on the trainees' respective training stages, differentiating between stage 3 & 4 and stage 5 & 6. Following the performance of the Mann-Whitney II test, results indicated that, across all three categories, the outcomes from the higher-stage group (Stage 5 & Stage 6) did not significantly differ from those of the lower-stage group (Stage 3 & Stage 4). Conversely, when feedback was stratified based on the quantity of surgeries conducted, notable distinctions emerged. In the category of anatomical accuracy, the higher-quantity group (250-1000) exhibited superior results compared to the lower-quantity group (0-250). However, in the categories of learning and overall satisfaction, no statistically significant differences were observed. This implies that more experienced surgeons provide more positive feedback, underscoring success of the urogenital simulator in achieving enhanced anatomical accuracy.

[0127] The manufacturing methodology employed in relation to the urogenital simulator described above has application in relation to penile implant surgery, an also offers an opportunity for creation of simulators tailored to specific patient profiles or application cases, for example, as educational tools for urological surgeries related to cancer, including procedures for testicular or prostate cancer patients. The urogenital simulator described can recreate tactile properties of tissues and the hands-on feeling of, for example, tissue during penile implant procedures. This feature positions it as a valuable tool not only for penile implant surgery but also for collecting force data during various urological surgeries, thereby offering an innovative solution for comprehensive surgical education and training.

[0128] Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiment and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.

[0129] REFERENCES

[0130] [1], Gaba D. The future vision of simulation in health care. Qual Saf Health Care.

[0131] 2004;13(Suppl 1):S2-S10. doi: 10.1136 / qshc.2004.009878

[0132] [2], Andrei Adrian Kozan, Luke Huiming Chan & Chandra Shekhar Biyani (2020)

[0133] Current Status of Simulation Training in Urology: A Non-Systematic Review, Research and Reports in Urology, , 111-128, DOI: 10.2147 / RRU.S237808

[0134] [3], Witthaus, M.W., Saba, P., Melnyk, R., Ajay, D., Ralph, D., Van Renterghem, K.,

[0135] Warren, G., Munarriz, R., and Ghazi, A. (2020). The Future of Penile Prosthetic Surgical Training Is Here: Design of a Hydrogel Model for Inflatable Penile Prosthetic Placement Using Modern Education Theory. The Journal of Sexual Medicine 17(11), 2299-2306.

[0136] [4], Lentz, Aaron & Rodriguez, Dayron & Davis, Leah & Apoj, Michel & Kerfoot, B. &

[0137] Perito, Paul & Henry, Gerard & Jones, LeRoy & Carrion, Rafael & Mulcahy, John & Munarriz, Ricardo. (2018). Simulation Training in Penile Implant Surgery: Assessment of Surgical Confidence and Knowledge with Cadaveric Laboratory Training. Sexual Medicine. 6. 10.1016 / j.esxm.2018.09.001.

[0138] [5], Li, J.Z., Maguire, T.A., Zou, K.H., Lee, L.J., Donde, S.S., and Taylor, D.G. (2022).

[0139] Prevalence, Comorbidities, and Risk Factors of Erectile Dysfunction: Results from a Prospective Real-World Study in the United Kingdom. Int. J. Clin. Pract. 2022

[0140] [6], Kessler, A., Sollie, S., Challacombe, B., Briggs, K., and Van Hemelrijck, M. (2019).

[0141] The Global Prevalence of Erectile Dysfunction: a review. BJU Int. 124(4), 587-599.

[0142] [7], McCabe, M.P., Sharlip, I.D., Atalla, E., Balon, R., Fisher, A.D., Laumann, E., Lee,

[0143] S.W., Lewis, R., and Segraves, R.T. (2016). Definitions of Sexual Dysfunctions in Women and Men: A Consensus Statement from the Fourth International Consultation on Sexual Medicine 2015. The Journal of Sexual Medicine 13(2), 135-143.

Claims

CLAIMS1. A tissue mimicking material comprising: an elastomeric solid foam, the foam comprising gas pockets dispersed in an elastomeric material matrix; and a liquid lubricant arranged within the gas pockets of the elastomeric solid foam.

2. A tissue mimicking material according to claim 1, wherein the foam comprises an open cell foam.

3. A tissue mimicking material according to claim 1, wherein the foam comprises a closed cell foam.

4. A tissue mimicking material according to any preceding claim, wherein the tissue mimicking material has a density in the range 0.35 to 0.60 g / cm3.

5. A tissue mimicking material according to any preceding claim, wherein the gas pockets have a diameter between 150 pm and 3000 pm.

6. A tissue mimicking material according to any one of claims 1 to 4, wherein the gas pockets have a diameter between 160 pm and 2700 pm.

7. A tissue mimicking material according to any preceding claim, wherein the gas pockets have an average diameter between 300 pm and 450 pm.

8. A tissue mimicking material according to any preceding claim wherein the elastomeric solid foam material has a Shore Hardness in a range between 12.0 and 13.5.

9. A tissue mimicking material according to any preceding claim, wherein the elastomeric material comprises a plastic or rubber material..

10. A tissue mimicking material according to any preceding claim, wherein the liquid lubricant fills at least a portion of the gas pockets of the elastomeric foam.

11. A tissue mimicking material according to any preceding claim, wherein the liquid lubricant partially fills at least a portion of the gas pockets of the elastomeric foam.

12. A tissue mimicking material according to any preceding claim, wherein the liquid lubricant coats an inner surface of at least a portion of the gas pockets of the elastomeric foam.

13. A tissue mimicking material according to any preceding claim, wherein the liquid lubricant comprises a water based lubricant.

14. A tissue mimicking material according to claim 13, wherein the liquid lubricant has a viscosity at room temperature in the range 2000cP to 3000cP.

15. A tissue mimicking material according to any preceding claim, wherein the liquid lubricant has a lubricity coefficient of friction in the range 0.1 to 0.2.

16. A tissue mimicking material according to any preceding claim, wherein the liquid lubricant comprises liquid soap.

17. A tissue mimicking material according to any one of claims 1 to 12, wherein the liquid lubricant comprises an oil based lubricant.

18. A tissue mimicking material according to claim 17, wherein the liquid lubricant has a viscosity at room temperature in the range 20cP to 70cP.

19. A tissue mimicking material according to claim 17 or claim 18, wherein the liquid lubricant has a lubricity coefficient of friction in the range 0.05 to 0.10.

20. A tissue mimicking material according to any preceding claim comprising an erectile tissue mimicking material, or a bone marrow mimicking material, or an alveolar lung tissue mimicking material,21. A surgical phantom comprising a tissue mimicking material according to any one of claims 1 to 20.

22. A surgical phantom according to claim 21, comprising a urogenital surgical phantom, or a skeletal surgical phantom.

23. A surgical phantom according to claim 22, comprising a penile surgical phantom.

24. A method of manufacturing a tissue mimicking material, the method comprising: forming an elastomeric solid foam, the foam comprising gas pockets dispersed in an elastomeric material matrix; and providing a liquid lubricant within the gas pockets of the elastomeric solid foam.

25. A method according to claim 24, wherein forming an elastomeric solid foam comprises: providing a curable elastomeric compound.

26. A method according to claim 25, wherein providing a curable elastomeric solid foam by mixing a powder volume of powdered silicon formulation with a liquid volume of water to form a curable silicon compound.

27. A method according to any one of claims 25 or 26, wherein the method comprises allowing the compound to cure.

28. A method according to any one of claims 24 to 27, wherein providing a liquid lubricant within the gas pockets of the elastomeric solid foam comprises: introducing the liquid lubricant into the elastomeric solid foam.

29. A method according to any one of claims 25 to 28, wherein providing a liquid lubricant within the gas pockets of the elastomeric solid foam comprises: mixing the liquid lubricant into the curable elastomeric compound.

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