A PROCESS FOR PROVIDING A TEXTILE WITH ELECTRICAL CONDUCTIVITY PROPERTIES

Abstract

The present invention relates to a process for producing an electrically conductive composite textile article, comprising a step of providing at least part of a textile article with a biopolymer, wherein at least part of said biopolymer comprises an electrically conductive material. The invention also relates to an electrically conductive composite textile article comprising a textile article and a biopolymer, wherein at least part of said biopolymer is provided with an electrically conductive material; and to a yarn, or a fabric, or a garment, consisting of, or essentially consisting of a biopolymer that can be produced by a microorganism, wherein at least part of said biopolymer is provided with an electrically conductive material.

Claims

1. A process for producing an electrically conductive composite textile article (1), wherein at least part of a textile article (2, 5) is provided with a biopolymer (3), and wherein at least part of said biopolymer (3) is provided with an electrically conductive material (4).

2. Process according to claim 1, wherein the step of providing at least part of a textile article (2, 5) with a biopolymer (3) comprises a step of contacting at least part of said textile article (2, 5) with a culture of biopolymer-producing microorganisms, and culturing said biopolymer-producing microorganisms, so that at least one biopolymer (3) is produced on said textile article (2, 5).

3. Process according to claim 2, wherein said culture of biopolymer-producing microorganisms further comprises said electrically conductive material (4), or wherein said electrically conductive material (4) is provided to said biopolymer (3) after said biopolymer (3) is produced on said textile article (2, 5).

4. A process according to claim 1, wherein at least part of said textile article (2, 5) is coupled with a separately produced biopolymer (3).

5. Process according to claim 4, wherein said separately produced biopolymer (3) is provided at least in part with said electrically conductive material (4) before or after being coupled to said textile article (2, 5).

6. Process according to claim 1, wherein said biopolymer (3) is provided to said textile article (2, 5) according to a pattern.

7. Process according to claim 1, wherein said electrically conductive material (4) is applied to said biopolymer (3) according to a pattern.

8. Process according to claim 1, wherein said textile article (2, 5) is selected from the group consisting of a yarn (5), a fabric (2) and a garment.

9. Process according to claim 8, wherein said textile article (2, 5) is a yarn (5) and wherein at least part of said yarn (5) is provided with said biopolymer (3).

10. Process according to claim 1, wherein said biopolymer (3) is selected from microbial cellulose, microbial collagen, cellulose/chitin copolymer, microbial silk, and mixture thereof.

11. Process according to claim 1, wherein said electrically conductive material (4) is a carbonaceous material, selected from the group consisting of activated carbon, high surface area carbon, graphene, graphite, activated charcoal, carbon nanotubes, carbon nanofibers, activated carbon fibers, graphite fibers, graphite nanofibers, carbon black and mixtures thereof.

12. Process according to claim 1, further comprising a step of providing at least part of said biopolymer (3) with at least a softening agent.

13. Process according to claim 1, further comprising a step of providing at least part of said biopolymer (3) with at least one electrically insulating polymer selected from the group consisting of PU, PA, PP, PLA, PBT, PET, and silicone.

14. An electrically conductive composite textile article (1) comprising a textile article (2, 5) and a biopolymer (3), wherein at least part of said biopolymer (3) is provided with an electrically conductive material (4).

15. Electrically conductive composite textile article (1) according to claim 14, wherein said electrically conductive material (4) is provided to said biopolymer (3) as a pattern of electrically conductive material (4).

16. Electrically conductive composite textile article (1) according to claim 14, wherein said biopolymer (3) is provided to said textile article (2, 5) as a pattern of biopolymer (3).

17. Electrically conductive composite textile article (1) according to claim 14, wherein said textile article (2, 5) is selected from the group consisting of a yarn (5), a fabric (2) and a garment.

18. Electrically conductive composite textile article (1) according to claim 14, wherein at least part of said biopolymer (3) is coated with at least one electrically insulating polymer selected from the group consisting of PU, PA, PP, PLA, PBT, PET, and silicone.

19. A yarn, or a fabric, or a garment, consisting of of a biopolymer produced by a microorganism, wherein at least part of said biopolymer is provided with an electrically conductive material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0105] The invention will now be described, by way of example, with reference to the accompanying drawings, which have to be interpreted as illustrative and non-limiting schematic representations of exemplary embodiments of the invention. Also, according to common practice, the various features of the drawing are not necessarily to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity.

[0106] In the accompanying drawings:

[0107] FIG. 1 shows an embodiment of the composite textile article of the invention;

[0108] FIG. 2 shows an embodiment of the composite textile article of the invention, wherein the biopolymer is provided as a pattern of biopolymer;

[0109] FIG. 3 shows an embodiment of the composite textile article of the invention, wherein the electrically conductive material is provided as a pattern of conductive material;

[0110] FIG. 4 shows an embodiment of the composite textile article of the invention, wherein the biopolymer is provided as a pattern of biopolymer;

[0111] FIGS. 5A, 5B and 5C, show an embodiment of the present invention wherein the textile article is a yarn.

DETAILED DESCRIPTION OF THE INVENTION

[0112] In the present description, when reference is made to a fabric, this definition includes the fabric present in a garment or clothing article.

[0113] FIG. 1 schematically represents a perspective view of a portion of an exemplary electrically conductive composite textile article 1 according to the invention.

[0114] According to FIG. 1, the textile article is a fabric 2, in particular a woven fabric.

[0115] The fabric 2 is provided with a biopolymer 3, for example microbial cellulose, which comprises an electrically conductive material 4, for example a carbon based electrically conductive ink.

[0116] In the embodiment shown in FIG. 1, the whole or substantially the whole biopolymer 3 is provided with the electrically conductive material 4 in a homogeneous or substantially homogeneous manner.

[0117] According to embodiments, the electrically conductive material 4 in the electrically conductive composite textile article 1, after drying, may be in an amount ranging from 0.005% to 7.5% by weight, preferably from 0.01% to 5% by weight of the weight of the electrically conductive composite textile article 1.

[0118] For example, an electrically conductive material 4 may be applied by impregnating at least the biopolymer 3 with the conductive material.

[0119] According to embodiments, the biopolymer 3 may be grown directly onto the fabric 2.

[0120] For example, the fabric 2 may be contacted, at least in part, with a culture of biopolymer-producing microorganisms, which may be cultured to produce at least one biopolymer 3 onto the fabric 2.

[0121] According to embodiments, the biopolymer 3 is microbial cellulose.

[0122] For example, microbial cellulose can be produced by culturing strains of Acetobacter bacteria, such as strains of Acetobacter xylinum, and/or by culturing strains of Gluconacetobacter, such as strains of Gluconacetobacter hansenii.

[0123] A culture comprising biopolymer-producing microorganisms may be provided to a textile article according to known methods. For example, at least part of the textile article may be dipped into a culture comprising microorganisms to be impregnated with the culture. In other examples, the culture of microorganisms may be poured or sprayed onto the textile article. Subsequently, the electrically conductive composite textile article may be washed, to remove residual microorganisms, and dried.

[0124] In FIG. 1, the fabric 2 is provided with a stripe of biopolymer 3 comprising an electrically conductive material 4.

[0125] According to embodiments of the invention, when the biopolymer 3 is to be provided to a textile article according to a pattern and/or according to a predetermined defined shape, the biopolymer 3 may be produced by culturing biopolymer-producing microorganism in shaped containers, according to known methods, and subsequently applied to the textile article, e.g., to a fabric 2.

[0126] According to embodiments, when the biopolymer 3 is to be provided to a textile article according to a pattern and/or according to a predetermined defined shape, the biopolymer 3 may be grown directly on the textile article.

[0127] For example, a culture comprising biopolymer-producing microorganisms may be poured or sprayed on at least part of the textile article through a template, i.e., a stencil. Subsequently, the biopolymer-producing microorganism may be grown to obtain a shaped biopolymer 3 on the textile article.

[0128] Advantageously, when the template or stencil is removed after the biopolymer is grown on the textile article, e.g., a fabric, a biopolymer having a defined shape and/or pattern may be obtained.

[0129] In FIG. 1, the fabric 2 is provided with a stripe of biopolymer 3 comprising an electrically conductive material 4.

[0130] As above mentioned, the electrically conductive material 4 may be provided to the biopolymer 3, for example, by impregnating at least part of the biopolymer 3 with such conductive material 4, e.g., by contacting at least part of the biopolymer 3 with a carbon-based conductive ink.

[0131] According to embodiments, the culture including biopolymer-producing microorganisms further comprises the electrically conductive material. In this case, advantageously, the electrically conductive composite textile article 1 of the invention may be obtained according to a one-step process.

[0132] According to embodiments, when a culture including biopolymer-producing microorganisms and an electrically conductive material is used, the electrically conductive material 4 in the culture may be in an amount in the range of from 0.00005% to 3% by weight, preferably from 0.0001% to 1% by weight of the total culture medium weight.

[0133] For example, a fabric 2 may be contacted with a culture including biopolymer-producing microorganisms and an electrically conductive material 4, optionally using a template or a stencil. Subsequently, microorganisms may be grown in order to produce a biopolymer 3 including the conducive material 4.

[0134] According to embodiments, at least part of the biopolymer 3 may with provided with at least a softening agent.

[0135] According to embodiments, the culture including biopolymer-producing microorganisms may further comprise a softening agent.

[0136] For example, a fabric 2 may be contacted with a culture including biopolymer-producing microorganisms and a softening agent, in order to produce a biopolymer 3 including the softening agent directly onto the fabric 2.

[0137] According to embodiments, the culture including biopolymer-producing microorganisms may further comprise an electrically conductive material 4 and a softening agent.

[0138] According to embodiments, when the culture including biopolymer-producing microorganisms comprises a softening agent, the culture comprises the softening agent in an amount ranging from 0.5% to 2% by weight, preferably from 0.8 to 1.2% by weight of the final culture weight that is applied to the textile.

[0139] As above discussed, suitable softening agents are, for example, those disclosed in the European patent application number EP3476996A1, “A process for preparing a composite textile article including a biopolymer layer produced by microorganisms”, claiming priority from EP17198751.4, in the name of the present applicant.

[0140] Preferably, the softening agent is a silicone softening agent. Preferred silicone softening agents are micro-silicone softening agents.

[0141] For example, a suitable micro-silicone softening agent is a micro-silicone emulsion wherein micro-silicone has a particle size ranging from below 80 nm to 10 nm, preferably from below 60 nm to 10 nm, more preferably ranging from 40 nm to 10 nm, wherein the particle size is measured by Dynamic Light Scattering. For example, Ceraperm® 3P Liq. and SANSIL MIC 3145 are exemplary micro-silicone emulsions suitable to be used in the process of the invention. Ceraperm® 3P Liq. and SANSIL MIC 3145 are currently commercially available.

[0142] The softening agent may be sprayed onto the biopolymer 3, after that it has been provided to the textile article, e.g., to the fabric 2. Additionally or alternatively, the biopolymer 2 may be impregnated with the softening agent, e.g., by dipping into the softening agent in liquid form or into a solution or dispersion comprising it.

[0143] According to embodiments, the softening agent may be provided also to the fabric 2. For example, a fabric 2 provided with a biopolymer 3, optionally including an electrically conductive material 4, may be impregnated with a softening agent.

[0144] According to embodiments, the composite textile article 1 may comprise a plurality of stipes of biopolymer 3 including an electrically conductive material 4, wherein at least two stripes have different orientation.

[0145] For example, a fabric 2 may be provided with a first stripe of biopolymer 3 including an electrically conductive material 4 and, optionally, at least a second stripe, said second stripe being oriented according to a predetermined angle with respect to said first stripe.

[0146] Also, for example, a fabric 2 may be provided with a first stripe and a second stripe of biopolymer 3 including an electrically conductive material 4, wherein the second stripe may be perpendicular to said first stripe. Optionally, the fabric may further comprise a third stripe of biopolymer 3 including an electrically conductive material 4 which is oriented according to a predetermined angle with respect to both the first stripe and the second stripe.

[0147] According to embodiments, the electrically conductive composite textile article 1 is flexible. In this case, advantageously, when the electrically conductive composite textile article 1 comprises one or more stripes of biopolymer 3 including an electrically conductive material 4, the composite textile article 1 results to be particularly suitable for the production of strain gauges.

[0148] Strain gauges, also known as extensometers, are devices that are, per se, known in the art, and are suitable to measure strain on an object, i.e., to measure of deformation of an object relative to a reference length.

[0149] According to embodiments, the electrically conductive composite textile article 1 is particularly suitable for the production of strain gauges when it is provided with one or more stipes of biopolymer 3 including an electrically conductive material 4. For example, a plurality of stripes of biopolymer 3 may be provided to the fabric according to a plurality of different directions, for example to form a star, e.g., a 5-pointed star.

[0150] According to embodiments, the biopolymer 3 and/or the electrically conductive material 4 may be provided according to a ring shape.

[0151] As above mentioned, according to embodiments, the biopolymer 3 may be provided to the fabric 2 according to a pattern. For example, the biopolymer 3 may be provided to the fabric 2 as a plurality of stripes of biopolymer 3. According to embodiments, the biopolymer 3 and/or the conductive material 4 may be provided according to a pattern of parallel stripes, as shown, for example, in FIG. 2, which show a perspective view of a portion of an exemplary embodiment of the electrically conductive composite textile article 1 according to the present invention.

[0152] In particular, FIG. 2 shows a fabric 2 which is provided with a pattern of parallel stripes of biopolymer 3, which includes an electrically conductive material 4.

[0153] Similarly to FIG. 1, also in the embodiment represented in FIG. 2, in each stripe of biopolymer 3, the whole or substantially the whole biopolymer 3 is provided with the conductive material 4 in a homogeneous or substantially homogeneous manner.

[0154] According to embodiments, when the biopolymer 3 is provided to a textile article according to a pattern, each portion of the pattern may have different dimension and/or thickness and/or may include a different amount of electrically conductive material 4.

[0155] In this case, advantageously, it is possible to obtain, for each pattern and element thereof, the desired value of electrical resistance in a precise and reliable way.

[0156] For example, different elements of the pattern may have different values of electrical resistance. For example, each element of the pattern may have sheet resistance (also called “surface resistivity”) in the range from 10.sup.2 Ohm/sq about to about 10.sup.9 Ohm/sq.

[0157] For example, considering the embodiment schematically represented in FIG. 2, the stripes of biopolymer 3 may have different dimension and/or different thickness. The stripes may contain different amounts of conductive material 4. For example, each stripe may contain the electrically conductive material 4 in an amount ranging from 0.005% to 7.5% by weight, preferably from 0.01% to 5% by weight of the weight of the electrically conductive composite textile.

[0158] Advantageously, when the electrically conductive material 4 is provided according to a pattern of parallel stripes, the composite textile article 1 of the invention results to be particularly suitable for the production of unidirectional touchpads. For example, considering the exemplary embodiment of FIG. 2, the stripes of biopolymer 3 including an electrically conductive material 4 may be connected, e.g., singularly, to a sensing device, to measure the capacity of each stripe.

[0159] FIG. 3 shows a perspective view of a portion of another embodiment of the composite textile article 1 of the invention.

[0160] FIG. 3 schematically shows a fabric 2 provided on one of its sides with a biopolymer 3, which covers substantially the entirety of the fabric 2.

[0161] In the embodiment of FIG. 3, the biopolymer 3 is schematically represented in the form of a continuous layer, i.e., as a layer of biopolymer 3 that covers continuously (i.e. substantially without interruptions or without interruption) the fabric 2.

[0162] In the embodiment of FIG. 3, the electrically conductive material 4 is provided to the biopolymer according to a pattern, in particular as a plurality of parallel stripes.

[0163] The biopolymer layer 3 may be produced directly on the fabric 2, by culturing biopolymer-producing microorganisms directly on the fabric 2, as above discussed. The electrically conductive material 4 may be subsequently provided to at least part of the biopolymer 3. When the conductive material 4 is to be provided to the biopolymer 3 according to a pattern, the electrically conductive material 4 is preferably applied to the biopolymer 3 by printing. For example, a pattern of carbon-based ink may be printed to a biopolymer 3, e.g., microbial cellulose, according to a selected pattern and/or shape.

[0164] In embodiments, the conductive material 4 may be provided to a biopolymer 2 according to a pattern, for example, as a plurality of parallel stripes.

[0165] In embodiments, the electrically conductive material 4 may be provided to the biopolymer 3, e.g., by printing, and subsequently, the biopolymer 3 including the conductive material 4 may be coupled with a textile article, e.g. a fabric 2. In embodiments, the textile article, e.g., a fabric 2, is provided with a biopolymer 3 and, subsequently, an electrically conductive material 4 is applied to at least part of the biopolymer 3.

[0166] Similarly to the embodiment represented in FIG. 2, also the exemplary embodiment of the composite textile article 1 of the invention represented in FIG. 3 is suitable for the production of unidirectional touchpads.

[0167] In fact, in the embodiment of FIG. 3, the electrically conductive material 4 is provided to the biopolymer 3 as a plurality of parallel stripes which may be connected to a sensing device to measure the capacity of each stripe.

[0168] FIG. 4 shows perspective view of a portion of a further exemplary embodiment of the electrically conductive composite textile article 1 which comprises a pattern of biopolymer 3 including an electrically conductive material 4.

[0169] In particular, in FIG. 4, a fabric 2 is provided with a plurality of square elements of biopolymer 3, arranged according to perpendicular rows and columns.

[0170] FIG. 4 schematically represents an embodiment of the composite textile 1 wherein, in each square element, the biopolymer 3 is provided with the conductive material 4 in a homogeneous or substantially homogeneous manner.

[0171] In embodiments, the elements of biopolymer 3 may include all the same or substantially the same amount of electrically conductive material 4.

[0172] In embodiments, the elements of biopolymer 3 may include different amounts of electrically conductive material 4. For example, each element of biopolymer 3 may include the electrically conductive material 4 in an amount ranging from 0.005% to 7.5% by weight, preferably from 0.01% to 5% by weight of the weight of the electrically conductive composite textile.

[0173] In embodiments, the elements of biopolymer 3 may have different dimension and/or different thickness.

[0174] FIG. 4 schematically shows and embodiment wherein the elements of the pattern of biopolymer 3 have a substantially square shape.

[0175] According to embodiments, the elements of the pattern of biopolymer 3 may have any geometrical shape. For example, one or more elements of a pattern of biopolymer 3 may have a polygonal shape (rectangular, square, triangular, irregular, etc.), or a curved shape (e.g., circular, oval, elliptical) or a shape comprising both straight portions and curved portions.

[0176] According to embodiments, the biopolymer 3 may be provided as a continuous or substantially continuous layer to the fabric 2, and the electrically conductive material 4 may be provided to at least part of such biopolymer 3 according to a desired pattern, e.g., a plurality of elements arranged in columns and rows, preferably perpendicular rows and columns. According to embodiments, the biopolymer 3 and/or the electrically conductive material 4 may be provided to the fabric 2 as grid of biopolymer 3 and/or electrically conductive material 4.

[0177] Advantageously, when the electrically conductive material 4, or the biopolymer 3 including the conductive material 4, is provided according to a pattern of rows and columns of elements, preferably perpendicular rows and columns, or according to a grid pattern, the composite textile article 1 of the invention results to be particularly suitable for the production of bidirectional touchpads. For example, considering the exemplary embodiment of FIG. 4, the square elements of biopolymer 3 including an electrically conductive material 4 may be connected, singularly, to a sensing device, to measure the capacity of each element of biopolymer 3.

[0178] The embodiments shown in FIGS. 1-4 may preferably provide the presence of electrical connections (not shown) configured to electrically connect the patterns of electrically conductive material 4 to a detection device.

[0179] For example, the detection device may be configured to evaluate the capacitance value of one or more patterns of electrically conductive material 4 for the capacitive sensing of touch events.

[0180] A suitable detection device and its relevant use may be the one as described in the European patent application No. EP19174913.4 having the following title: “COMPOSITE YARN FOR THE POSITION SENSITIVE CAPACITIVE TOUCH SENSING”, claiming priority from EP18172676.1, and in the European patent application No. EP19199244.5 having the following title: “CAPACITIVE TOUCH SENSOR”, claiming priority from EP18196531.0. Such European patent applications are in the name of the present Applicant and the contents of which is incorporated herein by reference as if set forth in its entirety.

[0181] FIGS. 5A, 5B and 5C show an exemplary embodiment of the invention wherein the textile article is a yarn 5. In particular, FIG. 5A schematically shows a cross-section of a yarn 5, FIG. 5B schematically shows a cross-section of a yarn 5 provided (namely, coated, in the case of FIGS. 5B and 5C) coated with a biopolymer 3 and FIG. 5C schematically shows a cross-section of an electrically conductive composite textile 1 according to the invention, wherein the textile article is yarn 5, which is coated with a biopolymer 3 including a conductive material 4.

[0182] According to FIGS. 5A, 5B and 5C, the yarn 5 may be provided with a coating of biopolymer 3, i.e., with a biopolymer 3 which substantially envelops the yarn 5. A conductive material 4 may be subsequently applied. For example, a yarn 5 may be impregnated with a culture of biopolymer-producing microorganisms, which may be cultured in order to grow the biopolymer 3 directly onto the yarn 5. Subsequently, the yarn 5 provided with a biopolymer 3 may be impregnated with an electrically conductive material 4, e.g., a conductive ink, to obtain a composite textile 1 having conductive properties, in this case, a composite yarn having electrical conductivity properties.

[0183] In embodiments, the culture of biopolymer-producing microorganisms may include at least an electrically conductive material 4. In this case, advantageously, the yarn 5 may be provided with a biopolymer 3 including a conductive material 4 according to a one-step process.

[0184] As above mentioned, a culture containing biopolymer-producing microorganisms, optionally containing an electrically conductive material 4, may be provided to a yarn through known methods.

[0185] According to embodiments, a culture containing biopolymer-producing microorganisms, optionally containing an electrically conductive material 4, may be provided to a yarn through the process discloses in the European patent application number EP19179217.5, “A process for providing a culture of microorganisms to an elongated element”, claiming priority from international application PCT/EP2018/065506, in the name of the present applicant.

[0186] For example, according to EP19179217.5, as well as to PCT/EP2018/065506, a culture containing biopolymer-producing microorganisms may be provided to a yarn by means of an apparatus comprising a feeding device having an outlet for dispensing such culture containing biopolymer-producing microorganisms from the outlet, and a yarn source to supply a yarn to the feeding device, wherein the apparatus is configured so that the culture containing microorganisms contacts at least part of the yarn when the culture is dispensed from the outlet. In this case, when a certain amount of culture is provided to the yarn, a certain amount of culture is dispensed from the outlet in order to feed to the yarn a fixed amount of culture that provides a sufficient amount of culture to the yarn, avoiding excessive culture being wasted. In other words, the dispensing of the culture may be adjusted so that, advantageously, the culture is dispensed from the outlet of the feeding device at a flow rate selected so that the culture envelops the yarn but is prevented from falling from the yarn, and from drying out at the outlet.

[0187] As above mentioned, the culture containing biopolymer-producing microorganisms, may optionally further comprise an electrically conductive material 4 and/or a softening agent. In this case, preferably, the culture may include an electrically conductive material in an amount in the range of from 0.0001% to 1% by weight of the total culture medium weight.

[0188] Advantageously, when the textile article is a yarn 5, the process of the invention allows for the production of an electrically conductive composite yarn, i.e., a yarn having electrical conductivity properties. Such electrically conductive composite yarn may be used in addition to or as an alternative to the currently available electrically conductive yarns.

[0189] According to an aspect of the present invention, the electrically conductive biopolymer, maintains the same, or substantially the same structural characteristics (e.g., crystal structure, nano-porous network structure) of the biopolymer when it does not include the conductive material.

[0190] Advantageously, in embodiments, the biopolymer may be provided with the electrically conductive material in a homogeneous or substantially homogeneous manner; in other words, the concentration of the electrically conductive material may substantially constant in the biopolymer, or in a portion thereof.

[0191] According to embodiments, the electrically conductive biopolymer may be tailored into a clothing item, e.g., a garment, or worked into a yarn.

[0192] According to embodiments, an item, in particular a textile item of article such as, for example, a yarn, a fabric, or a garment, or a portion thereof, may consist of, or essentially consist of the electrically conductive biopolymer. As above mentioned, the biopolymer can be grown and provided with an electrically conductive material. The biopolymer, before and/or after being provided with the conductive material may be worked into a yarn, a fabric or a garment, according to methods that are known, per se, in the art.

[0193] The present invention provides for several advantages. For example, the present invention allows for the production of article having electrical conductivity properties in an easy, fast, and cost-effective way.

[0194] Moreover, the present invention allows to obtain an article having electrical conductivity properties which is reliable and that may be used for several applications, in particular in the textile field.

[0195] Additionally, according to the present invention, the conductive material may be easily included into the biopolymer, without jeopardizing the structure of the biopolymer.