Conductive foam

Abstract

A conductive foam comprises: (i) a conductive polymer composition comprising a mixture of a conductive polymer and an elastomer; the conductive polymer composition being adsorbed onto (ii) a polymer foam. The conductive foam has conductivity and impedance suitable for use as an electrode to monitor human function and transmit stimulation thereto. The conductive foam (e.g., using an elastomer and foam with the same polymer) is prepared by: providing a polymer foam; providing a solution of the conductive polymer composition in a solvent; applying the solution to the polymer foam; and removing the solvent to produce a dried conductive foam.

Description

Technical Field

[0001] This invention relates to a conductive foam material and a method for manufacturing the same. The invention also relates to the applications and uses of the foam material. Background Technology

[0002] Conductive materials are useful in a wide variety of applications, particularly in healthcare settings, where electrodes are used to record electrical signals from the body (e.g., in electrocardiograms and electroencephalograms) and to electrically stimulate the body (e.g., during physical therapy).

[0003] Metals are the most commonly used materials for manufacturing conductive materials. Therefore, electrodes used in healthcare are typically wet electrodes made of metallic silver or silver chloride, which require skin preparation and conductive gel to achieve electrical contact with the skin.

[0004] This technology has significant limitations. First, skin preparation techniques (such as debridement of dead skin cells) may create wounds on sensitive skin, and the gel itself may cause allergic reactions. Second, the gel dries quickly, necessitating frequent replacement of the electrodes and / or the gel. Third, it is necessary to wash the skin and hair that have come into contact with the gel after use, which can be an uncomfortable and inconvenient process for patients with limited mobility.

[0005] Furthermore, the rigidity and stiffness of metals, as well as the need for conductive gels, have hindered the wider adoption of wearable electrodes in clinical, long-term monitoring, and home care applications, despite the established health benefits of the various applications that require these electrodes.

[0006] Conductive materials that do not require gels are promising alternatives for these applications. Several types of non-metallic conductive materials have been developed in commercial and academic settings, but these materials are typically manufactured as rigid structures coated with silver or gold to achieve conductivity. Therefore, most commercially available conductive materials used as dry electrodes are very rigid and can cause comfort problems similar to or even worse than those of wet metal electrodes, making them unsuitable for comfortable long-term recording or clinical use. Furthermore, the coatings used themselves are inherently less durable, as they eventually wear down, increasing impedance and degrading signal quality.

[0007] Flexible conductive materials have also been developed to allow for the fabrication of softer, smaller electrodes. These materials consist of a hard conductive material (such as a metal) coated onto a softer material, with the aim of achieving sufficiently high conductivity while maintaining the elastic properties of the softer material; however, a common problem with these types of electrodes is delamination. The mechanical mismatch between the flexible substrate and the conductive coating leads to moisture ingress, delamination, and subsequent loss of conductivity, as well as potential skin reactions.

[0008] Furthermore, carbon-derived compounds such as carbon nanotubes or graphene fibers have shown promise as metal alternatives, but dispersing them in flexible substrates can be challenging, making production potentially expensive and difficult. More importantly, carbon nanotubes have been shown to be cytotoxic and cause skin inflammation, limiting their use in bioelectronics applications.

[0009] An example of a conductive material is disclosed in EP 4245797 A, namely a self-healing conductive elastomer comprising PEDOT:PSS and a polyborosiloxane-based polymer.

[0010] Conductive polymers (CPs) have attracted considerable interest in flexible bioelectronics due to their excellent electrochemical properties and relatively low manufacturing costs. However, CPs are brittle and rigid, and have not yet been successfully used as electrodes in healthcare applications.

[0011] Therefore, there is a need for a conductive material that has high electrical conductivity but also high elasticity, and is suitable for use in healthcare environments without causing irritation or toxicity to humans.

[0012] Therefore, the object of the present invention is to provide an alternative conductive material for use as an electrode for monitoring biological signals or for manufacturing such electrodes. A particular embodiment aims to provide a conductive material that can be used as a dry electrode without gel or skin preparation, particularly a flexible, soft, comfortable, and / or compressible material suitable for long-term use and possessing signal quality comparable to wet metal electrodes. Summary of the Invention

[0013] The present invention provides a conductive foam comprising: (i) a conductive polymer composition comprising a mixture of a conductive polymer and an elastomer; and (ii) a polymer foam.

[0014] The conductive polymer and / or elastomer (or conductive polymer composition) is soluble in organic solvents or aqueous solvents. In the embodiments described in the following examples, the conductive polymer and elastomer are soluble in organic solvents.

[0015] Elastomers and polymer foams may be composed of or contain the same polymer. Alternatively or additionally, the elastomer may be composed of or contain polyurethane. For example, both the elastomer and the polymer foam may contain polyurethane.

[0016] Conductive foam may contain at least 25% by weight (e.g., 40-60% by weight) of a conductive polymer composition.

[0017] Conductive foam has conductivity and impedance suitable for use as electrodes to monitor human function and transmit stimulation to it. Electrodes and clothing used on the human body contain conductive foam.

[0018] The conductive polymer composition can be prepared by dissolving conductive polymer particles and elastomer particles in an organic solvent. The conductive polymer and elastomer particles can be dry particles.

[0019] Conductive foam can be prepared by the following method, which includes:

[0020] Provide polymer foam;

[0021] A solution of the conductive polymer composition in a solvent was prepared using the method described above.

[0022] Apply the solution to the polymer foam; and

[0023] Remove the solvent to produce dry, conductive foam.

[0024] Conductive foams can also be prepared by the following method, which includes:

[0025] Provide polymer foam;

[0026] A solution of a conductive polymer composition in a solvent is provided, the conductive polymer composition comprising a conductive polymer and an elastomer;

[0027] Apply the solution to the polymer foam; and

[0028] Remove the solvent to produce a dry, conductive foam.

[0029] The solvent used in this method can be an organic solvent or an aqueous solvent. In the embodiments described in the following examples, the solvent used in the method is an organic solvent. Detailed Implementation

[0030] The present invention provides a conductive foam comprising:

[0031] (i) a conductive polymer composition comprising a mixture of a conductive polymer and an elastomer; and

[0032] (ii) Polymer foam.

[0033] The conductive polymer composition is suitably attached (e.g., adsorbed) onto a solid polymer foam and remains attached during the use of the foam (i.e., during the bending, compression, and re-expansion of the foam).

[0034] Typically, conductive polymer compositions comprise 5-40 wt% of a conductive polymer and 60-95 wt% of an elastomer, more preferably 10-30 wt% of a conductive polymer and 70-90 wt% of an elastomer. In specific embodiments described in more detail below, the conductive polymer composition comprises about 20-25 wt% of a conductive polymer and about 75-80 wt% of an elastomer. It has been found that by incorporating the elastomer into the foam, the conductive polymer providing the desired conductivity exhibits reduced delamination between itself and the foam, preferably little or no delamination, resulting in a long service life for the final product, which retains its function despite repeated bending during use.

[0035] The conductive polymer composition may be applied to the foam in spray or liquid form (typically in a solvent-containing form); further details are set forth elsewhere. After drying to remove the solvent, the conductive polymer composition typically constitutes at least 25%, suitably at least 30%, more suitably at least 40%, and / or 75% or less, suitably 70% or less, more suitably 60% or less of the total weight of the conductive foam. More typically, the conductive polymer composition constitutes 40% to 60% of the total weight of the conductive foam. Preferably, the conductive polymer composition constitutes 40% to 50% of the total weight of the conductive foam, for example, 45.5% of the total weight of the conductive foam in the specific examples prepared and used below. This percentage can vary depending on the loading of the conductive polymer composition onto the foam; some applications requiring higher conductivity may have a higher loading, i.e., a higher weight percentage of the conductive polymer composition based on the total weight of the conductive foam.

[0036] The conductive foam (i.e., the final product) may contain up to 30% by weight, or up to 24% by weight, or up to 20% by weight, or up to 16% by weight, or up to 10% by weight of a conductive polymer. Alternatively or additionally, the conductive foam may contain 1% or more, 2% or more, or 3% or more, or 4% or more, or 5% or more of a conductive polymer. For example, the conductive foam may contain 2-16% by weight, or 3-24% by weight, or 4-20% by weight of a conductive polymer. Preferably, the conductive foam contains 4-20% by weight of a conductive polymer.

[0037] The materials used for polymeric foams can generally be virtually any polymer capable of providing a stable solid polymeric foam. Suitable polymers for foams are conventional and common in the art, including polyurethane, polystyrene, and polyethylene. Mixtures of polymers and copolymers can also be used. Furthermore, polymeric foams are typically non-conductive before being combined with conductive polymer compositions. Additionally, the foam can be open-cell or closed-cell. When using closed-cell foams, these foams are preferably dissolved in a solvent or at least partially dissolved in a solvent—thus, at least swelling in the solvent, thereby promoting the adhesion of the conductive polymer. Good results have been obtained using nearly closed-cell foams.

[0038] The elastomeric component of the conductive polymer composition is described in more detail below. In a preferred embodiment of the invention, the elastomer and the polymer foam comprise the same polymer or are made from the same polymer. For example, both the elastomer and the foam may comprise polyethylene, or both the elastomer and the foam may comprise polystyrene. In a preferred embodiment, the polymer foam is polyurethane or comprises polyurethane, and in specific embodiments described in more detail below, the polymer foam comprises polyurethane and the elastomer comprises polyurethane.

[0039] The conductive polymer incorporated into the foam provides useful electrical conductivity properties to the conductive foam of the present invention. The electrical conductivity of the final product foam is suitably at least 3 siemens / cm (300 siemens / m (S / m)), more suitably at least 5 siemens / cm (500 siemens / m (S / m)) and / or suitably 30 siemens / cm (3000 siemens / m (S / m)) or less, or 10 siemens / cm (1000 siemens / m (S / m)) or less, or preferably 7 siemens / cm (700 siemens / m (S / m)) or less. Typically, the electrical conductivity of the final product foam is between 5 and 10 siemens / cm, preferably between 5 and 7 siemens / cm. To date, specific foams have been prepared using the conductive polymer poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), and electrical conductivity of several hundred S / m has been measured. The final foam can also have an impedance of up to 10 megohms, or more appropriately up to 50 kilohms.

[0040] Conductive polymers can also be referred to as intrinsically conductive polymers, and many examples known in the art are considered suitable for use in this invention. Polymers with lower conductivity can be loaded onto foams at higher weight percentages to provide the required conductivity for the final product. Suitable conductive polymers include poly(fluorene), polyphenylene, polypyrene, polyazine, polynaphthalene, polybenzodifuran dione, poly(pyrrole) (PPY), polycarbazole, polyindole, polyazepine, polyaniline (PANI), poly(thiophene) (PT), poly(3,4-ethylenedioxythiophene) (PEDOT), poly(p-phenylene sulfide) (PPS), poly(acetylene) (PAC), and poly(p-phenylenevinylene) (PPV). Widely used conductive polymers include polythiophene (an example being PEDOT), polyaniline, polyindole, and polypyrrole. Examples are described in the following literature: RA Green, NH Lovell, GG Wallace and L. A. Poole-Warren et al. (RA Green, NH Lovell, GG Wallace and L. A. Poole-Warren, “Conducting polymers for neural interfaces: Challenges in developing an effective long-term implant,” Biomaterials, vol. 29, no. 24–25, pp. 3393–3399, Aug. 2008).

[0041] Conductive polymers are often also water-dispersible or water-soluble. This facilitates application onto foam and subsequent partial removal during curing and drying.

[0042] Suitable conductive polymer compositions may contain one or more ionomers; suitably, they may contain a first ionomer with a negative charge and a second ionomer with a positive charge. Suitable conductive polymer compositions may contain mixtures or combinations of conductive polymers, and in the examples, we used a conductive polymer composition containing a mixture of two ionomers. In a particular embodiment, the conductive polymer composition contains PEDOT and PSS. For this combination, a PEDOT:sulfonate ratio of about 3:1 is particularly preferred.

[0043] As described above, the final product has a conductive polymer composition adsorbed onto the foam. This can be conveniently achieved by combining (i) a formulation (e.g., a solution) of the conductive polymer and elastomer in a solvent with (ii) a polymer foam, and then removing the solvent. Solvent removal leaves the conductive polymer and elastomer on the foam during the curing process, causing them to adhere to the foam.

[0044] The elastomer (and optionally, a conductive polymer) is soluble in organic or aqueous solvents. For example, both the elastomer and the conductive polymer are soluble in organic or aqueous solvents. In the embodiments described in the following examples, the elastomer and the conductive polymer are soluble in organic solvents. In other embodiments, the elastomer (and optionally, a conductive polymer) may be insoluble in aqueous solvents. For example, both the elastomer and the conductive polymer are insoluble in aqueous solvents.

[0045] Solvents can be removed through solvent exchange. For example, solvent exchange can be used to replace a first solvent (e.g., an organic solvent) with a second solvent (e.g., an aqueous solvent). The second solvent can be removed by a drying step. Solvent exchange steps (and drying steps) generally result in a more biocompatible / cellularly compatible final product (i.e., conductive foam) because it ensures that virtually all solvents (e.g., especially organic solvents) are removed and no residual solvent is left.

[0046] Suitable elastomers for use in this invention include: silicone rubber, elastomers based on polymeric organosilicon compounds, ether-based hydrophilic urethane, thermoplastic urethane, polyurethane, polystyrene, Pellethane® (in one example, specifically variant 80AE), and mixtures or copolymers thereof. The elastomer may be a thermoplastic elastomer comprising a mixture of polymers having both thermoplastic and elastomeric properties. Preferred elastomers are thermoplastic urethanes. Preferably, the elastomer does not contain borosilicates or polyborosilicates. In other words, the elastomer is preferably not a polyborosilicate.

[0047] Suitable elastomer formulations (typically solutions or suspensions) are prepared by dissolving or dispersing one or more elastomers in a solvent; these formulations can then be used to apply conductive polymer compositions to foams.

[0048] The solvent can be an organic solvent, including but not limited to ethanol, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), tetrahydrofuran (THF), chloroform, and mixtures thereof. The solvent can also be an aqueous solvent, including but not limited to mixtures of water and alcohols (e.g., ethanol and methanol). In some embodiments of the invention, the solvent is not an aqueous solvent. It should be understood that the solvent is suitably compatible with elastomers and conductive polymers, as well as with foams. Suitably, the elastomer and / or conductive polymer (preferably both) is soluble in organic solvents. Generally, the elastomer and / or conductive polymer (preferably both) is insoluble in aqueous solvents. Combinations of elastomers can be used; for example, a formulation may comprise a polyurethane-based elastomer and a polymeric silicone compound-based elastomer. Preferably, the formulation is a solution of polyurethane in a solvent (e.g., ethanol or DMAc).

[0049] In a particular embodiment of the present invention, a conductive foam is provided, comprising:

[0050] (i) A conductive polymer composition comprising 10-30% by weight of a conductive polymer and 70-90% by weight of an elastomer, wherein the conductive polymer is PEDOT:PSS or contains PEDOT:PSS, and the elastomer is a thermoplastic urethane elastomer or contains a thermoplastic urethane elastomer; and

[0051] (ii) Elastically compressible polymer foam.

[0052] Specific embodiments of the present invention prepared and used in the following examples include:

[0053] (i) a conductive polymer composition comprising a mixture of about 20 wt% PEDOT:PSS and about 80 wt% Pellethane 80AE; and

[0054] (ii) Elastically compressible polyurethane foam.

[0055] The conductive foam of the present invention has many advantageous uses, such as for use in electrodes or as part of electrodes. Thus, electrodes of the present invention for use on the human body comprise the conductive foam of the present invention. Another type of electrode for non-human use comprises the conductive foam of the present invention; in use, the electrode can be attached to any conductive surface, such as a conductive surface in a vehicle or transport vehicle. The electrode is suitably used with or includes a device for applying the foam to a surface under pressure, the device comprising, for example, straps or elastic bands or adhesive materials (e.g., tape). An advantage of the conductive foam of the present invention is that it can be used dry, for example without the need for gel.

[0056] Furthermore, clothing applied to the human body may contain the conductive foam according to the invention. The clothing may be a headband, glasses, goggles, or a face mask. Similarly, the conductive foam material can be used as electrodes in wearable devices.

[0057] The electrodes may further include rigid elements, such as disks or plates made of metal, for reinforcing the foam material. The rigid elements (e.g., disks) may be attached to one or more sides of the conductive foam for reinforcement. Alternatively or additionally, conductive wires may be applied to the conductive foam material to allow signals to be transmitted back and forth between the conductive foam electrodes and a monitoring device for patient monitoring or stimulation. In particular, wires may be incorporated into the conductive foam to produce wired sensors for biosignal recording or electrical stimulation.

[0058] The present invention also provides a method for (i) stimulating a patient, or (ii) recording signals from a patient, comprising (e.g., using electrodes as described above) applying conductive foam to the patient.

[0059] To prepare conductive foams, conductive polymers and elastomers are attached to the starting material foam, particularly by combining the conductive polymer and elastomer in a solvent and then removing the solvent. Typically, solvents are non-biocompatible; therefore, to prepare biocompatible conductive foams, all or substantially all of the solvent is removed.

[0060] Specifically, to prepare a conductive polymer composition, the method may include dissolving particles of a conductive polymer and particles of an elastomer in an organic solvent. The particles of the conductive polymer and elastomer may be dry particles; an advantage of this method is that it rapidly yields a solution of the conductive polymer and elastomer in the same non-aqueous solvent. The method is simplified, and a solvent exchange step is subsequently used appropriately to remove the organic solvent from the final product, particularly when intended for human use.

[0061] A specific method for preparing conductive foam, comprising:

[0062] Provide polymer foam;

[0063] A solution of the conductive polymer composition in a solvent is prepared according to the method described above.

[0064] Apply the solution to the polymer foam; and

[0065] Remove the solvent to produce dry, conductive foam.

[0066] Another specific method for preparing conductive foam includes:

[0067] Provide polymer foam;

[0068] A formulation (e.g., a solution) of a conductive polymer composition in a solvent is provided, said conductive polymer composition comprising a conductive polymer and an elastomer;

[0069] Applying a formulation (e.g., a solution) to a polymer foam; and

[0070] Remove the solvent to produce dry, conductive foam.

[0071] Preferably, the solvent used in the method is an organic solvent (i.e., not an aqueous solvent). Also preferably, the polymer foam and elastomer used in the method are made of or contain the same polymer.

[0072] The solvent (e.g., an organic solvent, such as DMAc) can be removed by solvent exchange with a second solvent (e.g., an aqueous solvent). The method may further include a drying step to remove the second solvent.

[0073] This method can be carried out in the absence of water (optionally, up to the solvent exchange step). This is because elastomers (e.g., polyurethane) can be very sensitive to water, especially at elevated temperatures. Therefore, all reasonable steps can be taken to minimize the presence of water (up to the solvent exchange step). For example, molecular sieves can be used to dry the organic solvent before use, and / or all glassware can be over-dried, and / or the elastomer (and conductive polymer) can be present in the form of dry granules, which are mixed with the organic solvent to form a solution (i.e., without forming an aqueous dispersion). The granules can also be oven-dried.

[0074] Elastomers (and conductive polymers) can be provided in a form in which they are ready to dissolve in a (organic) solvent to form a (organic) solution, for example, in granules or pellets or similar forms, rather than formed in situ from two or more components. The granules can be soluble, allowing solutions to be formed without the need for an aqueous dispersion. This method typically also does not require surfactants (or auxiliaries).

[0075] When implementing the method described above, the polymer foam can be a closed-cell foam. In this case, the method appropriately uses a solvent compatible with the polymer foam, meaning that the solvent is capable of dissolving or at least partially swelling the polymer foam. This compatibility allows the closed-cell foam to open sufficiently for conductive polymers and elastomers to adhere to it before the solvent is removed.

[0076] Therefore, the conductive foam of the present invention can be prepared by impregnating non-conductive foam with a conductive polymer (CP) composition, thereby making the foam material conductive. Typically, the solvent is then removed by a curing process, allowing the conductive polymer composition to dry and adhere to the foam, thus producing a conductive foam.

[0077] In the embodiments described in more detail below, the first step involves manufacturing a CP composition comprising one or more conductive polymers and one or more elastomers. Preferably, the conductive polymer composition comprises a mixture of conductive polymers dispersed in an elastomer solution or suspension (e.g., one or more elastomers dissolved in a solvent).

[0078] In the second step, the foam can be immersed or soaked in a conductive polymer composite solution, and then removed so that excess solution can drip off. The remaining solution can be removed by drying to obtain dry conductive foam.

[0079] In the final product, conductive polymers and elastomers can be chemically attached to or otherwise adsorbed onto the foam to create conductive foam. Elastically compressible conductive foam can be produced using elastically compressible foam. Findings include combining conductive polymers with elastomers, which provides flexibility and reduces the brittleness of the conductive polymer. Therefore, delamination between the conductive polymer and the foam is reduced after the inevitable compression and expansion during use. Conductive foam products retain their integrity and conductivity after repeated compression and expansion, thus serving as electrodes with advantageous durability and lifespan even when bent during use.

[0080] Conductive foam can be non-healable. In other words, conductive foam may not be self-healing or possess self-healing properties. Alternatively or additionally, conductive foam can be a composite material, preferably a monolithic composite material. In other words, conductive foam is preferably not a multilayer material and / or conductive foam is preferably not anisotropic.

[0081] Each or a combination of these characteristics of conductive foams can lead to improved stability, stretchability, flexibility, bendability, transparency, and / or electrical conductivity. They can also lead to increased cycle stability and / or deformability. Therefore, conductive foams can achieve increased electrical conductivity without negatively impacting mechanical / material properties and / or other functional properties.

[0082] Methods for preparing conductive foams preferably do not require the use of a separate insulating phase. This is typically because conductive foams are composite materials in which the elastomer and polymer foam contain the same polymer (e.g., polyurethane) or are composed of the same polymer (e.g., polyurethane). However, when an insulating phase is used (e.g., when the elastomer and polymer foam do not contain the same polymer or are composed of the same polymer), the insulating phase can be polyurethane. Seamless bonds can be formed between pure polyurethane and the conductive polymer composition (i.e., conductive polymer and / or elastomer). These bonds produce the desired mechanical properties.

[0083] Curing can be achieved through solvent exchange, which involves immersing the foam in a solution of the conductive polymer composite and then in water or an aqueous solution for one or more cycles. A gentler solvent removal process may also follow the curing or solvent exchange process. Alternatively, curing can be achieved through thermal curing. Or, curing can be achieved through solvent evaporation, where the evaporation method may include using an oven and / or reduced pressure. Regardless of the curing method used, it is preferable to remove all or substantially all solvents from the composition to ensure that the resulting conductive foam material is biocompatible. Preferably, the resulting conductive foam material meets the International Organization for Standardization (ISO) standards for cell compatibility in wearable and / or implantable devices.

[0084] The curing process may also include forming a film or forming a film on a substrate having a release layer. This has the advantage of allowing the conductive polymer composition to be applied directly to the polymer foam, thereby simplifying the process of coating polymer foams with complex 3D geometries with conductive polymers.

[0085] Using complex curing processes like those described above also means that this method is less dependent on very specific drying conditions (such as time, temperature, and humidity). This reduced dependence on these parameters results in conductive foam materials with greater stability and processability.

[0086] Compared to known methods, the method of the present invention is less prone to problems caused by over-mixing. Therefore, the method is not limited by specific mixing conditions and is easily scalable for industrial production of conductive foams. In the method of the present invention, the solution can be left to stand for about a month under heating or stirring conditions without any negative impact on mechanical and / or electrical properties.

[0087] The method of the present invention appropriately requires no additives or additional components, such as additional conductive fillers. Conductive polymer compositions are generally readily compatible with coating processes and / or capable of achieving high conductivity without the use of additional conductive fillers or additional process steps. This is typically due to the compatibility between the polymer and solvent system used (e.g., the use of organic solvents in combination with elastomers and / or polymer foams soluble in organic solvents). This compatibility allows for chemical bonding between the components of the reaction mixture, making it easier to seamlessly combine / integrate materials (e.g., conductive polymer compositions and polymer foams) and / or form stable, monolithic composite materials.

[0088] Specifically, the method of the present invention suitably does not rely on or involve the use of surfactants or other auxiliaries that may affect biocompatibility. The absence of such components and / or optional removal of any residual solvents can result in increased cell compatibility without significantly reducing conductivity.

[0089] In use, the resulting conductive elastomer foam material retains high conductivity and high elasticity, making it soft, flexible, and compressible. Applications of this material include any application requiring flexible conductive materials, such as wearable skin electrodes. Therefore, this material is suitable for integration into medical devices that include electrode components (e.g., for heart or brain monitoring) for healthcare settings such as clinics or home care. Other applications include preclinical research using electrodes and non-clinical commercial applications (e.g., selling consumer-grade electroencephalography (EEG) devices for gaming or personal health tracking).

[0090] Implementation

[0091] Therefore, the present invention provides the following embodiments:

[0092] 1. A conductive foam comprising:

[0093] (i) a conductive polymer composition comprising a mixture of a conductive polymer and an elastomer; and

[0094] (ii) Polymer foam,

[0095] The elastomer and polymer foam contain the same polymer.

[0096] 2. The conductive foam according to embodiment 1, wherein both the elastomer and the polymer foam comprise polyurethane.

[0097] 3. A conductive foam comprising:

[0098] (i) a conductive polymer composition comprising a mixture of a conductive polymer and an elastomer; and

[0099] (ii) Polymer foam,

[0100] The elastomer includes polyurethane.

[0101] 4. A conductive foam comprising:

[0102] (i) at least 25% by weight of a conductive polymer composition comprising a mixture of a conductive polymer and an elastomer; and

[0103] (ii) Polymer foam.

[0104] 5. The conductive polymer according to any one of the foregoing embodiments, wherein both the elastomer and the conductive polymer are soluble in organic solvents.

[0105] 6. The conductive polymer according to any one of embodiments 1 to 4, wherein both the elastomer and the conductive polymer are soluble in an aqueous solvent.

[0106] 7. The conductive foam according to any one of the foregoing embodiments, wherein the conductive polymer composition comprises:

[0107] 5-40% by weight of conductive polymer; and

[0108] 60-95% elastomer by weight.

[0109] 8. The conductive foam according to embodiment 7, wherein the conductive polymer composition comprises:

[0110] 10-30% by weight of conductive polymer; and

[0111] 70-90% elastomer by weight.

[0112] 9. The conductive foam according to any one of the foregoing embodiments, comprising at least 25% by weight of a conductive polymer composition.

[0113] 10. The conductive foam according to any one of the foregoing embodiments, comprising 40-60% by weight of a conductive polymer composition.

[0114] 11. The conductive foam according to any one of the foregoing embodiments, wherein the conductive foam comprises 4-20% by weight of a conductive polymer.

[0115] 12. The conductive foam according to any one of the foregoing embodiments, wherein the conductive polymer comprises one or more ionomers, such as a first ionomer with a negative charge and a second ionomer with a positive charge.

[0116] 13. The conductive foam according to embodiment 12, wherein the conductive polymer is poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS).

[0117] 14. The conductive foam according to any one of the foregoing embodiments, which is prepared by a method comprising: combining (i) a solution of a conductive polymer and an elastomer in a solvent with (ii) a polymer foam, and removing the solvent.

[0118] 15. The conductive foam according to embodiment 14, wherein the solvent is an aqueous solvent.

[0119] 16. The conductive foam according to embodiment 14, wherein the solvent is organic.

[0120] 17. The conductive foam according to embodiment 16, wherein the method includes removing the organic solvent by solvent exchange with a second solvent.

[0121] 18. The conductive foam according to embodiment 17, wherein the method includes a drying step to remove the second solvent.

[0122] 19. The conductive foam according to embodiment 17 or 18, wherein the second solvent is an aqueous solvent.

[0123] 20. The conductive foam according to any one of embodiments 16 to 19, wherein the solvent includes ethanol, DMAc, DMSO, DMF or a mixture of two or more thereof, preferably DMAc or DMSO or a mixture thereof, especially DMAc.

[0124] 21. The conductive foam according to any one of the foregoing embodiments has a conductivity of 5 Siemens / cm or greater.

[0125] 22. The conductive foam according to any one of the foregoing embodiments has a conductivity of 5 to 10 siemens / cm and / or an impedance of up to 10 megohms.

[0126] 23. The conductive foam according to any one of the foregoing embodiments, comprising:

[0127] (i) A conductive polymer composition comprising 10-30% by weight of a conductive polymer and 70-90% by weight of an elastomer, wherein the conductive polymer is PEDOT:PSS or contains PEDOT:PSS, and the elastomer is a thermoplastic urethane elastomer or contains a thermoplastic urethane elastomer; and

[0128] (ii) Elastically compressible polymer foam.

[0129] 24. An electrode for use on the human body, comprising a conductive foam according to any one of the foregoing embodiments.

[0130] 25. A garment for application to the human body, comprising an electrode or conductive foam according to any one of the foregoing embodiments.

[0131] 26. An electrode for non-human use, such as an electrode for a conductive surface in a vehicle or transport vehicle, comprising a conductive foam according to any one of embodiments 1 to 23.

[0132] 27. A method for preparing a conductive polymer composition, comprising:

[0133] The conductive polymer particles and elastomer particles are dissolved in an organic solvent.

[0134] 28. The method for preparing a conductive polymer composition according to Embodiment 27, wherein the particles of the conductive polymer and the elastomer are dry particles.

[0135] 29. The method for preparing a conductive polymer composition according to embodiment 27 or 28, wherein the conductive polymer composition is defined according to any one of embodiments 1 to 23.

[0136] 30. A method for preparing conductive foam, comprising:

[0137] Provide polymer foam;

[0138] A solution of the conductive polymer composition in a solvent is prepared according to any one of Embodiments 27 to 29;

[0139] Apply the solution to the polymer foam; and

[0140] Remove the solvent to produce dry, conductive foam.

[0141] 31. The method for preparing conductive foam according to embodiment 30, wherein the method includes removing organic solvent by solvent exchange with a second solvent.

[0142] 32. The method for preparing conductive foam according to embodiment 31, wherein the method includes a drying step to remove a second solvent.

[0143] 33. The method for preparing conductive foam according to embodiment 32, wherein the second solvent is an aqueous solvent.

[0144] 34. The method for preparing conductive foam according to any one of embodiments 30 to 33, wherein the organic solvent includes ethanol, DMAc, DMSO, DMF or a mixture of two or more thereof.

[0145] 35. The method for preparing conductive foam according to embodiment 34, wherein the organic solvent includes DMAc or DMSO or a mixture thereof, particularly DMAc.

[0146] 36. A method for preparing a conductive foam according to any one of embodiments 1 to 23, comprising:

[0147] Provide polymer foam;

[0148] A solution of a conductive polymer composition in a solvent is provided, the conductive polymer composition comprising a conductive polymer and an elastomer;

[0149] Apply the solution to the polymer foam; and

[0150] Remove the solvent to produce dry, conductive foam.

[0151] 37. The method for preparing conductive foam according to embodiment 36, wherein the solvent is an organic solvent, and the method includes removing the organic solvent by solvent exchange with a second solvent.

[0152] 38. The method for preparing conductive foam according to embodiment 37, wherein the method includes a drying step to remove a second solvent.

[0153] 39. The method for preparing conductive foam according to embodiment 38, wherein the second solvent is an aqueous solvent.

[0154] 40. The method for preparing conductive foam according to any one of embodiments 37 to 39, wherein the organic solvent includes ethanol, DMAc, DMSO, DMF, or a mixture of two or more thereof.

[0155] 41. The method for preparing conductive foam according to embodiment 40, wherein the organic solvent includes DMAc or DMSO or a mixture thereof, particularly DMAc.

[0156] 42. The method according to any one of embodiments 30 to 41, wherein the polymer foam is a closed-cell foam, and the solvent is compatible with the polymer foam and is capable of dissolving the foam or at least partially swelling the foam.

[0157] Example

[0158] Each step of the manufacturing process is described in more detail in the following examples (Examples 1 to 3).

[0159] Example 1 - Preparation of a solution of a conductive polymer composition

[0160] Polyurethane (PU) granules made from Pellethane 2363-80AE (an ether-based polyurethane elastomer) were dissolved in DMAc solvent at a concentration of 5% (w / v). The solution was then placed in a silicone oil bath at 60°C and mechanically stirred at 300 rpm for 24 hours.

[0161] After verifying that the PU granules had fully swelled in DMAc, lithium perchlorate (LiClO4) was added at a concentration of 0.3 mmol / g PU. The PU / LiClO4 solution was then stirred at 300 rpm in a silicone oil bath at 60°C for 10 hours or longer.

[0162] Apply poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) pellets (Orgacon) to the desired loading amount (on a dry basis) (i.e., Add to the PU / DMAC solution.

[0163] The solution was then heated in an oil bath at 60°C and stirred at 180 rpm for 3 days until PEDOT was completely dispersed throughout the solution.

[0164] Polyurethane is highly sensitive to water, especially at elevated temperatures. Therefore, all reasonable steps have been taken to minimize the presence of water. For example, molecular sieves are used to dry the solvent before use, all glassware is thoroughly dried, and the raw PU material is also oven-dried.

[0165] Example 2 - Preparation of Conductive Foam Electrode (Part 1)

[0166] Polyurethane foam (3M foam: product number 1100C30, ID 7100141468, UPC 05902658102851, 05902658102844, 05902658102837) was cut into cylinders, each cylinder having a diameter of 1 cm (0.1 m).

[0167] Maintain the foam cylinders in their initial uncompressed shape and place each foam cylinder on top of the syringe needle (for manipulation). The sample is then prepared for the dip-coating procedure.

[0168] Foam cylinders were dipped into a 20 wt% conductive polymer composite solution prepared by the method described in Example 1. The process involved briefly (less than 1 second) immersing the cylinders, followed by transferring them to a water immersion / soaking solution. They were allowed to soak in water for more than 2 minutes, then excess water was gently blotted away with paper towels to allow them to dry. The foam cylinders were then placed in a fume hood until dry (i.e., until no water remained on the surface).

[0169] Repeat the dip-coating process twice, then place the foam in an oven at 37°C to dry overnight.

[0170] Example 3 - Assembly of Conductive Foam Electrode

[0171] The coated foam electrode, prepared by the method explained in Example 2, was connected to a silver-plated copper wire to achieve connection with the hardware. The conductivity of the electrode foam was measured to be in the range of 5-7 Siemens / cm.

[0172] impedance

[0173] To evaluate the impedance of the exemplary electrodes, a dual-probe device was used on human skin. The working electrode was placed on the ulnar styloid process, and the reference / counter electrode was located in the antecubital fossa. Both electrodes were conductive foam electrodes, connected by wire and attached to the skin using disposable adhesive. Impedance measurements were then performed using electrical impedance spectroscopy (EIS).

[0174] Therefore, conductive foams suitable for a wide range of applications in healthcare and other fields have been prepared.

Claims

1. A conductive foam comprising: (i) a conductive polymer composition comprising a mixture of a conductive polymer and an elastomer; and (ii) Polymer foam, The elastomer and the polymer foam contain the same polymer.

2. The conductive foam according to claim 1, wherein both the elastomer and the polymer foam comprise polyurethane.

3. A conductive foam comprising: (i) a conductive polymer composition comprising a mixture of a conductive polymer and an elastomer; and (ii) Polymer foam, The elastomer described therein comprises polyurethane.

4. A conductive foam comprising: (i) at least 25% by weight of a conductive polymer composition, said conductive polymer composition comprising a mixture of a conductive polymer and an elastomer; and (ii) Polymer foam.

5. The conductive polymer according to any one of the preceding claims, wherein both the elastomer and the conductive polymer are soluble in an organic solvent.

6. The conductive polymer according to any one of claims 1 to 4, wherein both the elastomer and the conductive polymer are soluble in an aqueous solvent.

7. The conductive foam according to any one of the preceding claims, wherein the conductive polymer composition comprises: 5-40% by weight of conductive polymer; and 60-95% elastomer by weight.

8. The conductive foam of claim 7, wherein the conductive polymer composition comprises: 10-30% by weight of conductive polymer; and 70-90% elastomer by weight.

9. The conductive foam according to any one of the preceding claims, comprising at least 25% by weight of a conductive polymer composition.

10. The conductive foam according to any one of the preceding claims, comprising 40-60% by weight of a conductive polymer composition.

11. The conductive foam according to any one of the preceding claims, wherein the conductive foam comprises 4-20% by weight of a conductive polymer.

12. The conductive foam according to any one of the preceding claims, wherein the conductive polymer comprises one or more ionomers, such as a first ionomer with a negative charge and a second ionomer with a positive charge.

13. The conductive foam according to claim 12, wherein the conductive polymer is poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS).

14. The conductive foam according to any one of the preceding claims, prepared by a method comprising: The solution of (i) conductive polymer and elastomer in solvent is combined with (ii) polymer foam, and the solvent is removed.

15. The conductive foam according to claim 14, wherein the solvent is an aqueous solvent.

16. The conductive foam of claim 14, wherein the solvent is organic.

17. The conductive foam of claim 16, wherein the method comprises removing the organic solvent by solvent exchange with a second solvent.

18. The conductive foam of claim 17, wherein the method includes a drying step to remove the second solvent.

19. The conductive foam according to claim 17 or 18, wherein the second solvent is an aqueous solvent.

20. The conductive foam according to any one of claims 16 to 19, wherein the solvent comprises ethanol, DMAc, DMSO, DMF or a mixture of two or more thereof, preferably DMAc or DMSO or a mixture thereof, particularly DMAc.

21. The conductive foam according to any one of the preceding claims, having a conductivity of 5 Siemens / cm or greater.

22. The conductive foam according to any one of the preceding claims, having a conductivity of 5 to 10 siemens / cm and / or an impedance of up to 10 megohms.

23. The conductive foam according to any one of the preceding claims, comprising: (i) a conductive polymer composition comprising 10-30% by weight of a conductive polymer and 70-90% by weight of an elastomer, wherein the conductive polymer is PEDOT:PSS or contains PEDOT:PSS, and the elastomer is a thermoplastic urethane elastomer or contains a thermoplastic urethane elastomer; and (ii) Elastically compressible polymer foam.

24. An electrode for use on the human body, comprising a conductive foam according to any one of the preceding claims.

25. A garment for application to the human body, comprising an electrode or conductive foam according to any one of the preceding claims.

26. An electrode for non-human use, such as an electrode for a conductive surface in a vehicle or transport, comprising a conductive foam according to any one of claims 1 to 23.

27. A method for preparing a conductive polymer composition, comprising: The conductive polymer particles and elastomer particles are dissolved in an organic solvent.

28. The method for preparing a conductive polymer composition according to claim 27, wherein the particles of the conductive polymer and elastomer are dry particles.

29. The method for preparing a conductive polymer composition according to claim 27 or 28, wherein the conductive polymer composition is defined according to any one of claims 1 to 23.

30. A method for preparing conductive foam, comprising: Provide polymer foam; The method according to any one of claims 27 to 29 is used to prepare a solution of the conductive polymer composition in a solvent; Apply the solution to the polymer foam; and Remove the solvent to produce dry, conductive foam.

31. The method for preparing conductive foam according to claim 30, wherein the method includes removing the organic solvent by solvent exchange with a second solvent.

32. The method for preparing conductive foam according to claim 31, wherein the method includes a drying step to remove the second solvent.

33. The method for preparing conductive foam according to claim 32, wherein the second solvent is an aqueous solvent.

34. The method for preparing conductive foam according to any one of claims 30 to 33, wherein the organic solvent comprises ethanol, DMAc, DMSO, DMF, or a mixture of two or more thereof.

35. The method for preparing conductive foam according to claim 34, wherein the organic solvent comprises DMAc or DMSO or a mixture thereof, particularly DMAc.

36. A method for preparing a conductive foam according to any one of claims 1 to 23, comprising: Provide polymer foam; A solution of a conductive polymer composition in a solvent is provided, the conductive polymer composition comprising a conductive polymer and an elastomer; Apply the solution to the polymer foam; and Remove the solvent to produce dry, conductive foam.

37. The method for preparing conductive foam according to claim 36, wherein the solvent is an organic solvent, and the method includes removing the organic solvent by solvent exchange with a second solvent.

38. The method for preparing conductive foam according to claim 37, wherein the method includes a drying step to remove the second solvent.

39. The method for preparing conductive foam according to claim 38, wherein the second solvent is an aqueous solvent.

40. The method for preparing conductive foam according to any one of claims 37 to 39, wherein the organic solvent comprises ethanol, DMAc, DMSO, DMF, or a mixture of two or more thereof.

41. The method for preparing conductive foam according to claim 40, wherein the organic solvent comprises DMAc or DMSO or a mixture thereof, particularly DMAc.

42. The method according to any one of claims 30 to 41, wherein the polymer foam is a closed-cell foam, and the solvent is a polymer compatible with the polymer foam and capable of dissolving the foam or at least partially swelling the foam.