CONDUCTIVE POLYMERIC COMPOSITION AND METHOD FOR PREPARING THE CONDUCTIVE POLYMERIC COMPOSITION

Abstract

The invention provides a composition for a conductive polymeric material suitable for the production of electrodes for recording electrophysiological signals, such as electrocardiogram (EGG), electromyogram (EMG), electroencephalogram (EEG), etc and signals related to the impedance variation of the body or skin, both deriving from active and passive measures (for example, breathing, electrodermal response, etc.). For this purpose a formulation containing FEDOT and ionic liquids has been developed. The formulation according to the invention can be used generically in the context of detecting bioelectric signals and can be applied on wearable items, in particular in fabric, such as for example garments of different shapes, so as to be in direct contact with the areas of the body subject to detection. The artifacts include diving artefacts, such as watertight suits, and for water sports and submarine surveys, artifacts used in the medical and health sector such as plasters, elastic support bands and adhesive support bands and textile articles, including special fabrics such as bioceramics.

Claims

1. A conductive polymeric composition comprising PEDOT and one or more ionic liquids of general formula (I) ##STR00003## wherein R1 and R2 independently of each other are branched or cyclic linear alkyl groups, with chain C1-C15, preferably C1-C10, X is an anion selected from alkylsulphates, tosylate, Ccarboxylates-i-Cs, such as formate and acetate, halides such as fluorides, chlorides, bromides and iodides, borates and phosphates, such as tetrafluoro borate and hexafluorophosphate, sulphonates, wherein the conductive polymeric composition comprises an aqueous suspension comprising in % by weight: a PEDOT conductive polymer in an amount between about 0.2 and 10%, one or more ionic liquids in an amount between about 0.05-2.0%, a secondary dopant in an amount between about 0-50%, ratio (ionic liquid)/(conductive polymer) is between about 0.5 and 15, preferably between 0.66 and 2, water in an amount between about 30-99% by weight, wherein the conductive polymeric composition which is processed by evaporating the water in two evaporation stages, the first evaporation stage being carried out to obtain a viscosity of the mixture between about 100 and 10000 cP, the second evaporation stage for the almost complete elimination of the water, between the first and second evaporation stages the composition being applied on a support to constitute a textile electrode on said support.

2. Conductive polymeric composition according to claim 1 wherein the ionic liquids are selected from the group consisting of: 1-ethyl-3-methylimidazolium ethylsulphate (CAS: 342573-75-5), 1-butyl-3-methylimidazolium bromide (CAS number: 85100-77-2), 1-ethyl-3-methylimidazolium chloride (CAS number: 65039-09-0), 1-ethyl-3-methylimidazolium acetate (CAS number: 143314-17-4), 1-butyl-3-methylimidazolium acetate (CAS number: 284049 -75-8), 1-ethyl-3-methylimidazolium tosylate (CAS number: 328090-25-1), 1-methyl-3-propylimidazolium iodide (CAS number: 1 19171 -18-5), 1-decyl-3-methylimidazolium chloride (CAS number: 171058-18-7), and related mixtures.

3. The conductive polymeric composition of claim 1, wherein the ionic liquid comprises 1-butyl-3-methylimidazolium acetate, which is added in an amount of between about 0.1-2.0%.

4. The conductive polymeric composition of claim 1, wherein PEDOT is salified with anions selected from the group consisting of: perchlorate, tetrafluoroborate, hexafluorophosphate, nitrate, sulphate, chloride, tosylate, sulphonamides with fluorinated substituents such as bis ((trifluoromethyl) sulphonyl) -amide, bis ((perfluoroethyl) sulphonyl) amide, bis ((heptafluoro-propinyl) -sulphonyl) amide and bis ((nonafluoro-butinyl) sulphonyl) amide and sulphonates with fluorinated substituents, a triflate ion, nonafluorobuthane sulphonate and heptadecafluoroethane sulphonate.

5. The conductive polymeric composition of claim 1, wherein PEDOT is salified with Polystyrene Sulphonate.

6. The conductive polymeric composition of claim 1, wherein the secondary dopant is selected from: ethylene glycol, dimethylsulphoxide, dimethylformamide, methoxyethanol, diethylene glycol, dimethyl sulphate, xylitol, glycerol, sorbitol and meso-erythritol, and related mixtures.

7. The conductive polymeric composition of claim 1, further comprising cross-linkers and surfactants in an amount of 0.05-1.5% by weight.

8. A method Method for processing a conductive polymeric composition of claim 1, comprising the following steps: (i) mixing a suspension of PEDOT, any secondary dopant and the ionic liquid to generate a conductive polymeric composition; (ii) heating to thicken the conductive polymeric composition until a mixture viscosity of between about 100 and 10000 cP is obtained; (iii) applying an aliquot of the mixture obtained in step (ii) on a substrate suitable for being in contact with the epidermis; (iv) drying the mixture applied on the substrate obtained in the previous step (iii) for the complete elimination of the water.

9. The method of claim 8, wherein: (a) the thickening of the composition in step (ii) is stopped before a phase separation occurs between water and mixture containing the ionic liquid; (b) the thickening of the composition according to step (ii) is a heat treatment carried out by drying in a stove between 0 and 60 minutes at a temperature between 40 and 100° C., preferably 50-70° C.; (c) the application according to step (iii) is carried out with a printing technique chosen from: stencil, brush, screen printing; and/or (d) the drying of step (iv) leads to the realization of a textile electrode.

10-12. (canceled)

13. The method of claim 12, further comprising a stage (v) for manufacturing contacts for connecting the textile electrode with an electronic unit for reading electrical signals recorded by said electrode, when placed in contact with a portion of skin.

14. An electrode for recording bioelectric signals comprising the conductive polymeric composition of claim 1.

15. The electrode of claim 14, wherein the electrode is connected to reading electronics of a device for detecting bioelectric parameters.

16. An electrode comprising the conductive polymeric composition of claim 1 characterized by a skin/electrode impedance lower than about 1000 kΩ measured at room temperature and about 20 Hz, and preferably between about 25 and 250 kΩ.

17. A device for detecting bioelectric signals, wherein a sensor of said device comprises at least one electrode as set forth in claim 14.

18. The device of claim 17 wherein the bioelectronic signals are electrophysiological signals from: (a) passive measurements selected from the group consisting of: electrocardiogram, electromyogram, electroneurogram, electroencephalogram, electrooculogram, and electrodermal activity; or (b) active measures comprising electrodermal activity, bioimpedance, or breathing.

19. A product of manufacture comprising an electrode of claim 14.

20. The product of manufacture of claim 19, comprising artifacts and supports made of fabrics and materials suitable for being placed in direct contact with the epidermis.

21. The product of manufacture of claim 19, comprising or made of a material selected from the group consisting of: fabric, elastic fabric, non-woven fabric, rubbers, polyurethane foams, fibers, plastic films and relative combinations.

22. The product of manufacture of claim 21, fabricated as T shirts, sports T-shirts, waterproof suits, diving suits, artifacts for water sports or submarine surveys, artifacts used in a medical or a sanitary field, plasters, elastic support bands, adhesive support bands, textile products, or bioceramic fabrics.

23. A conductive polymeric composition thickener comprising an ionic liquid of general formula (I) ##STR00004## wherein R1 and R2 independently of each other are branched or cyclic linear alkyl groups, with an alkyl chain of between about C1-C15, or of between about C1-C10, wherein X is an anion selected from the group consisting of alkyl sulphates, tosylate, carboxylates C1-C5, formate or acetate, halides, fluorides, chlorides, bromides, iodides, borates, phosphates, tetrafluoro borate, hexafluorophosphate, and sulphonates.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0036] The invention will be better understood by referring to the detailed description when considered in combination with the non-limiting examples and the attached drawings, in which:

[0037] FIG. 1 shows a photograph of the electrode printed on bioceramic fabric (FIG. 1A) and of the back of the fabric on which the electrode was printed (FIG. 1B);

[0038] FIG. 2 shows the IR spectrum recorded on a PEDOT electrode: PSS with the addition of 1-ethyl-3-methylimidazolium printed on bioceramics;

[0039] FIG. 3 shows the IR spectrum recorded on a PEDOT electrode: PSS with the addition of 1-ethyl-3-methylimidazolium chloride printed on bioceramics;

[0040] FIG. 4 shows the IR spectrum recorded on a PEDOT electrode: PSS with the addition of 1-butyl-3-methylimidazolium bromide printed on bioceramics;

[0041] FIG. 5 shows the IR spectrum recorded on a PEDOT electrode: PSS with the addition of 1-butyl-3-methylimidazolium acetate printed on bioceramics;

[0042] FIG. 6 shows the IR spectrum recorded on a PEDOT electrode: PSS with the addition of 1-ethyl-3-methylimidazolium acetate printed on bioceramics;

[0043] FIG. 7 shows the IR spectrum recorded on a PEDOT electrode: PSS with the addition of 1-ethyl-3-methylimidazolium tosylate printed on bioceramics;

[0044] FIG. 8 shows the IR spectrum recorded on a PEDOT electrode: PSS with the addition of 1-methyl-3-propylimidazolium iodide printed on bioceramics;

[0045] FIG. 9 shows the IR spectrum recorded on a PEDOT electrode: PSS with the addition of 1-decyl-3-methylimidazolium chloride iodide printed on bioceramics;

[0046] FIG. 10 shows the IR spectrum recorded on a PEDOT electrode:

[0047] PSS printed on bioceramics;

[0048] FIG. 11 shows the IR spectrum recorded on bioceramic fabric;

[0049] FIG. 12 shows the impedance spectrum recorded for commercial

[0050] Ag/AgCI electrodes, dry and wet PEDOT:PSS base electrodes (without new additives) and PEDOT:PSS electrodes obtained using 1-ethyl-3-methylimidazolium ethylsulphate as an additive, object of the invention;

[0051] FIG. 13 shows the impedances recorded at 20 Hz for the electrodes of PEDOT:PSS printed on fabric and added with the various ionic liquids object of the invention;

[0052] FIG. 14 shows the ECG tracing recorded with a pair of PEDOT:PSS electrodes obtained using 1-ethyl-3-methylimidazole ethylsulphate as additive;

[0053] FIG. 15 shows the noise index values for the PEDOT electrodes:

[0054] PSS printed on fabric and added with the various ionic liquids object of the invention;

[0055] FIG. 16 shows the ECG of a male subject during mild physical activity;

[0056] FIG. 17 shows the ECG of the same male subject of FIG. 16, during intense physical activity;

[0057] FIG. 18 shows the ECG of a female subject during mild physical activity;

[0058] FIG. 19 shows the ECG of the same female subject, in the transition from moderate to intense physical activity;

[0059] FIG. 20 shows the traces of ECG and BREATH (acquired with impedance technique from the same electrodes used for ECG, simultaneously) acquired on a subject that alternates normal breathing with apnea;

[0060] FIG. 21 shows the traces of ECG and BREATH (acquired with impedance technique from the same electrodes used for ECG, simultaneously) acquired on the same subject during moderate physical effort (pedaling).

DETAILED DESCRIPTION OF THE INVENTION

[0061] In the context of the present invention, the term “bioelectric signals” or “electrophysiological” refers to identify the electrical signals that can be continuously measured by living beings in the form of current voltages. The best known bioelectric signals are the electrocardiogram, electroencephalogram, electromyogram, electrodermal activity and electrooculogram. Other signals, linked to active measurements on the subject, or that involve the injection of an alternating current of very small entity for the measurement of the impedance of the body or skin, and of its variations, such as measures of respiratory frequency using impedance techniques, impedance tomography or active electrodermal response, can also be considered within the scope of the present invention. The invention allows to detect bioelectric signals through polymeric electrodes printed on fabric. For example, the new formulation of the PEDOT, preferably PEDOT:PSS, described here, allows the acquisition of the signal without hydration or the use of gel or other additional layers of materials. The conductive composition according to the invention includes: the combination poly-(3,4-ethylenedioxytophene):anion, also simply called PEDOT, preferably the poly- (3,4-ethylenedioxytophene) combination: poly- (styrene-sulphonate) (called hereinafter PEDOT:PSS), and at least one ionic liquid of general formula (I):

##STR00002##

wherein

[0062] R1 and R2 independently of each other are branched or cyclic linear alkyl groups, with chain C.sub.1-C.sub.15, preferably C.sub.1-C.sub.10

[0063] X is an anion selected from alkylsulphates, tosylate, carboxylates C.sub.1-C.sub.5, such as for example formate and acetate, halides such as fluorides, chlorides, fluorides, bromides and iodides, borates and phosphates, such as tetrafluoro borate and hexafluorophosphate, sulphonates

[0064] taken individually or in a mixture.

[0065] The following compounds are preferred:

[0066] 1-ethyl-3-methylimidazolium ethylsulphate (CAS: 342573-75-5)

[0067] 1-ethyl-3-methylimidazolium chloride (CAS number: 65039-09-0)

[0068] 1-butyl-3-methylimidazolium bromide (CAS number: 85100-77-2)

[0069] 1-butyl-3-methylimidazolium acetate (CAS number: 284049-75-8)

[0070] 1-ethyl-3-methylimidazolium acetate (CAS number: 143314-17-4)

[0071] 1-ethyl-3 -methylimidazolium tosylate (CAS number: 328090-25-1)

[0072] 1-methyl-3-propylimidazolium iodide (CAS number: 119171-18-5)

[0073] 1-decyl-3-methylimidazolium chloride (CAS number: 171058-18-7).

[0074] A compound with the function of secondary dopant can be added to the PEDOT/ionic liquid combination, chosen from ethylene glycol, dimethylsulphoxide, dimethylformamide, methoxyethanol, diethylene glycol, dimethyl sulphate, xylitol, glycerol, sorbitol and meso-erythritol. These substances increase the crystallinity of the PEDOT, have the function of increasing the conductivity of the final composition and are widely known in the literature.

[0075] The ratios of the individual components of the composition are in the following percentages by weight with respect to the final mass of the solution:

[0076] Conductive polymer suspension (PEDOT) 49.9-99.9% (PEDOT concentration between 1-10%), therefore the composition of the invention has a conductive polymer concentration of 0.2-10%, secondary dopant 0-50%, ionic liquid 0.05-2.0%. Preferred is 1-butyl-3-methylimidazolium acetate, which is added in an amount of 0.1-2.0%; and the ratio (conductive polymer)/(ionic liquid) is comprised between 0.5 and 15, preferably between 0.66 and 2.

[0077] The above mentioned composition is suitable above all with the use of PEDOT:PSS.

[0078] In this case, cross-linkers known per se as GOPS (can be added 3-glycidoxypropyl-trimethoxysilane), typically in an amount of 0.05-1.5% by weight, with the aim of creating a bond between the various PEDOT:PSS particles in the suspension and subsequently in the polymer film. Furthermore, surfactants, such as for example dodecyl benzene sulphonic acid, can be added to decrease the surface tension between ink and substrate in order to improve the coating of the substrate by the ink.

[0079] The compositions thus identified have the appearance and characteristics of an ink, are in fact blue in color, and are applied as described below on textile supports and/or materials for wearable clothing in order to be used as electrodes for bioelectric measurements.

[0080] Ionic liquids have an unexpected thickening effect, since a slight heating (between 1 and 60 minutes in an oven at a temperature between 50 and 70° C.) is sufficient at the concentration of 1% to lead to the formation of a liquid with the right viscosity (between 100 and 10000 cP) for the applications according to the invention, in particular in the processes of screen printing, stencil or brush. The conductive compositions thus identified, also called inks below, are viscous but not gelled compositions. It should be remembered that the gel is characterized by a solid matrix in which a liquid phase is dispersed, and therefore has its own shape, unlike the compositions of the invention which, although very viscous, are not gels. In fact, the compositions of the invention are used before reaching gelation, which is intended as an irreversible condition in which the ink takes on its own shape characterized by a solid structure in which a liquid phase is incorporated and involves a worsening of the electrical characteristics of the molded electrodes. Within the scope of the present invention, the term “textile electrode” means an electrode prepared by applying the conductive composition of the invention directly onto a textile support capable of being placed in direct contact with the skin. The combination of conductive composition and support will be suitable to ensure the maintenance of the mechanical/sensorial characteristics of the fabric itself, such as flexibility, density in weight, comfort and fit, while maintaining the electrical characteristics unchanged even after washing in water or in the washing machine. The composition object of the invention allows to prepare this type of electrode by applying it with a brush or with printing techniques, such as for example the stencil or the screen printing. The viscosity of the ink is such as to allow to obtain a shape with defined contours on a support, such as a fabric, which can be used to create wearable articles. Within the scope of the present invention, therefore, application methods are excluded which provide for the manufacture of low viscosity inks, such as the spin coating technique, which in fact do not adapt to the application on textile supports, as they do not produce regular and standardized shapes.

[0081] As indicated above, the compositions according to the invention are aqueous suspensions which comprise (% by weight): [0082] conductive polymer (PEDOT) in an amount between 0.2 and 10% (generally obtained from commercial suspensions in which the concentration of conductive polymer is 49.9-99.9%), [0083] ionic liquid 0.05-2.0% (preferred is 1-butyl-3-methylimidazolium acetate, which is added in an amount of 0.1-2.0%), [0084] secondary dopant 0-50%, [0085] ratio (ionic liquid)/(conductive polymer) between 0.5 and 15, preferably between 0.66 and 2, [0086] water 30 - 99% by weight
and, once the mixture of the individual components is prepared, to obtain the textile electrodes according to the invention, the water is evaporated in two stages, the first being carried out until obtaining a viscosity of the mixture between 100 and 10000 cP measured under standard conditions, the second for the almost complete elimination of water. Between the first and second evaporation stages, the application will be carried out on the substrate.

[0087] These operating modes allow to obtain a constancy of characteristics, in terms of recorded bioelectric signals, which remains unchanged even after several washes of the wearable articles on which the textile electrodes are applied.

[0088] Not to mention that the process is particularly interesting from an industrial point of view as it is simple to carry out and allows at the same time to obtain easily standardized wearable articles.

[0089] A method for obtaining the formulation according to the invention comprises the following basic stages: [0090] (i) Mixing of the commercial suspension of the conductive polymer (PEDOT), of the secondary dopant and of the ionic liquid. The mixing can be carried out in the laboratory first manually with the aid of a glass rod and then placing the mixture thus prepared in an ultrasonic bath. It is preferable that the mixing is carried out immediately after the addition of the ionic liquid to the suspension of PEDOT due to the thickening effect of the additive. [0091] (ii) It is preferable that the use of the suspension indicated above is carried out within 3-4 hours from the mixing of the components, otherwise gelation phenomena occur, due to the presence of the ionic liquid, which risk leading to poor performance of the final composition. The gelation is evidenced by a phase separation in which in a first phase the conductive polymer is present together with the ionic liquid and in the second phase the water solvent is present. Once gelled, or having a continuous solid structure in which a liquid phase is incorporated, the composition cannot be returned to the initial fluid state and its characteristics are irreparably compromised, also compromising its subsequent formulation as ink to make the electrodes of the invention, since its electrical conductivity is at least one order of magnitude lower. Possible heat treatment of evaporation of the solvent and consequent thickening in order to obtain the appropriate chemical-physical properties for application on fabric, indicated by a viscosity of the mixture, which has the appearance of a viscous ink, between 100 and 10000 cP measured under standard conditions. The viscosity was measured with HAAKE ROTOVISCO 1 VISCOSIMETER. The heat treatment to obtain the aforementioned viscosity can be carried out in the air or by drying in an oven between 0 and 60 minutes at a temperature between 40 and 100° C., preferably 50 - 70° C. The viscosity indicated above is considered optimal for the subsequent steps of the application on the substrate. [0092] (iii) Application on a substrate suitable to be placed in contact with the epidermis of an aliquot of the composition obtained in step (ii) (as a non-limiting example, about 0.5 g is used for printing a 2 cm×2 cm square) through known printing techniques such as, for example, not limiting: stencil or brush, screen printing or other suitable techniques known per se. [0093] (iv) Stove drying of the products obtained in the previous stage (iii) for the elimination of the solvent (20°-150° C. for a time greater than 5 min) which usually consists of water and a possible secondary dopant added to the suspension of PEDOT. The electrode thus obtained and the surrounding fabric will be permanently impregnated with the ink mixture containing the conductive polymer and the ionic liquid which, due to the low vapor pressure, cannot evaporate.

[0094] At this stage of the preparation an electrode made of conductive polymeric material was obtained. We then move on to the next stage which is: [0095] (v) Manufacture of the contacts for the connection with the reading electronics. The ideal contacts are made with a conductive material wire and using a conductive glue (for example silver) to facilitate the charge transfer between the wire and the electrode.

[0096] A non-limiting list of suitable substrates to be placed in contact with the epidermis is as follows: fabric, elastic fabric, non-woven fabric, rubbers, polyurethane foams, fibers, plastic films, relative combinations and all the materials that can generally be used to make wearable products. The fabrics can be all conventional fabrics and technical fabrics made with natural, vegetable, synthetic fibers and their blends.

[0097] The strong point of the invention is the formulation of the preparation to be applied to the substrate which allows to obtain PEDOT electrodes for the recording of bioelectric signals without the use of gels or moisturizing solutions.

[0098] The formulation according to the invention can be used generically in the context of detecting bioelectric signals and can be applied on wearable articles, in particular in fabric, such as, for example, a shirt, so as to be in direct contact with the areas of the body subject to detection. The products on which to apply the formulation can be flexible and wearable products, including diving articles, such as watertight suits, and for water sports and underwater surveys, in particular articles used in the medical and health sector such as plasters, elastic support bands and adhesive support bands and textile products, including those made of special fabrics such as bioceramics.

[0099] Ionic liquids are used as thickeners for the production of the compositions of the invention.

[0100] The manufactured items are washable and it has been verified that after 20 washes they still maintained good electrical response characteristics. The compositions are suitable to be applied directly on the skin and the tests carried out have not detected skin irritation.

[0101] The compositions of the invention are suitable for being used in printing techniques as an ink would be used. They are applied when a certain amount of solvent (water +possibly secondary dopant) is still present which gives the appropriate viscosity for printing applications. The optimal quantity of solvent depends on the ionic liquid used and is between 40 and 99%. The application of the composition can be carried out until no phase separation has yet taken place or the material has acquired a well-defined proper shape, which differentiates it from a proper fluid. This condition occurs when a thick, viscous but not gelled viscous liquid is obtained. Depending on the printing applications, the viscosities can vary from 100 to 10000 cP measured under standard conditions.

[0102] In fact, the formulations described are suitable to be applied with printing techniques because they have an optimal final ratio between ionic liquid and conductive polymer between 0.05 and 2, preferably between 0.5 and 1.5. This ratio allows for constant electrical characteristics over time, combined with excellent resistance to washing, as well as allowing the electrical responses to be kept constant even with a great alternation of dry/wet skin cycles, typical of athletes.

[0103] In conclusion, the compositions to be used as inks on fabrics, and the electrodes for the detection of bioelectric parameters thus obtained, solve the problems of resistance to washing of the clothes on which the electrodes are applied and allow the bioelectrical parameters to be detected with constant results of a human body both in conditions of wet and dry skin and in alternating situations of dry/wet skin. A further advantage of the invention results from the ease of industrial implementation and relative standardization of the manufactured articles obtained. The following examples are illustrative of the invention and are in no case to be considered limitative of the relative scope.

EXAMPLES

[0104] An example of construction of the electrodes involves mixing the reagents with the following procedure.

[0105] The suspension of PEDOT:PSS PH 1000 in water (suspension purchased from Heraeus) is stirred in an ultrasonic bath (Bandelin Sonorex Super RK 510, power=2×320 W) for 10 min. The suspension of PEDOT:PSS, the secondary dopant and the ionic liquid are mixed in the proportions shown in table 1, taking care to maintain a good stirring, using a glass rod. The suspension obtained is placed in an ultrasonic bath for 10 min.

[0106] The composition is placed in a petri dish in order to have a liquid with a height of a few mm. The plate is placed in an oven at 70° C. until the material turns out to be a very viscous liquid (viscosity between 100 and 10000 cP). The preparation thus obtained was used to obtain textile electrodes in various embodiments.

TABLE-US-00001 TABLE 1 Composition of the various preparations object of the invention mass.sub.PEDOT:PSS(g) Secondary Mass.sub.secondary dopant(g) Ionic Mass.sub.ionic liquid(g) 8.90 Ethylene glycol 1.00 1-ethyl-3- 0.10 (Merck) methylimidazolium ethylsulphate (Sigma-Aldrich) 8.90 Dimethylsulphoxide 1.00 1-ethyl-3- 0.10 (Sigma-Aldrich) methylimidazolium ethylsulphate 8.75 Dimethylsulphoxide 1.00 1-ethyl-3- 0.25 methylimidazolium chloride (Sigma- Aldrich) 8.75 Dimethylsulphoxide 1.00 1-butyl-3- 0.25 methylimidazolium bromide (Sigma- Aldrich) 8.90 Dimethylsulphoxide 1.00 1-butyl-3- 0.10 methylimidazolium acetate (Sigma- Aldrich) 8.90 Dimethylsulphoxide 1.00 1-ethyl-3- 0.10 methylimidazolium acetate 8.90 Dimethylsulphoxide 1.00 1-ethyl-3- 0.10 methylimidazolium tosylate (Sigma- Aldrich) 8.90 Dimethylsulphoxide 1.00 1-methyl-3- 0.10 propylimidazolium iodide (Sigma- Aldrich) 8.98 Dimethylsulphoxide 1.00 1-decyl-3- 0.02 methylimidazolium chloride (Sigma- Aldrich)

Embodiment 1: Electrodes on Single Pieces of Fabrics Printed With Stencil

[0107] The electrode is made on bioceramic fabric with two stencil printing steps using a square mask with a side of 2 cm.

[0108] An aliquot of about 0.5 g of the viscous liquid prepared previously is used. The preparation is placed on one side of the square which identifies the printing area, and with the help of a spatula the composition is dragged onto the mask so as to make it come into contact with the fabric. In the printing area the fabric appears impregnated with ink with a strong blue color. The fabric is placed in an oven at 60° C. for about 15 minutes. A second printing step is subsequently carried out so that a greater quantity of preparation remains on the fabric. A professionally conducted print should not present lumps of PEDOT:PSS.

[0109] The electrode is dried in a stove for 30 min until the solvent consisting of water and secondary dopant has completely evaporated. FIG. 1 shows the photo of the electrode, using 1-ethyl-3-methylimidazolium ethylsulphate as an ionic liquid and as a secondary dopant dimethylsulphoxide, printed on fabric. The electrode and the surrounding fabric still appear impregnated with the ionic liquid which, due to the low vapor pressure, cannot evaporate.

[0110] The collectors for signal extraction are made by sewing a metal wire near a vertex of the square based on PEDOT which constitutes the electrode. The wire comes out from the back of the electrode as shown in FIG. 1B. An Ag-based conductive paint is placed in the interface between the metal wire and the PEDOT-based composition, in order to reduce the electrical contact resistances. The areas covered with Ag are then isolated with the aid of a silicone (polydimethylsiloxane, PDMS). The presence of the ionic liquid inside the conductive material is confirmed by the IR spectra (FIGS. 2-9) recorded on a bioceramic fabric for the various electrodes obtained. In addition, the IR spectra of the bioceramic fabric and of electrodes obtained with PEDOT:PSS only are shown in FIGS. 10 and 11. In the IR spectra of the PEDOT:PSS electrodes with ionic liquids, bands are observed at about 1577, 1164, 1057 and 622 cm.sup.−1 not present in the IR spectra of the fabric and the electrode in PEDOT:PSS printed on bioceramics.

[0111] These bands are related to the IR vibrations of the imidazole ring. In particular, the 622 cm.sup.−1 band can be attributed to the stretching of the group CH.sub.3(N)CN, while the 1164, 1057 and 1577 cm.sup.− bands are attributable to the stretching of the imidazole ring. These data demonstrate the presence in each electrode of the imidazole ionic liquids used as additives.

ECG Test (1)

[0112] The electrodes were used to acquire the ECG tracing of healthy volunteers. In particular, two textile electrodes were placed on the chest, with the skin dry and untreated, at a distance of about 10 cm, at the height of the xiphoid process, and an elastic band was used to maintain physical contact between the skin and electrode. The metal collectors have been connected to bench reading electronics (CH Instrument 660) to record both the impedance spectrum and the difference in electrical potential between the two electrodes. The impedance spectrum was recorded for commercial pre-gelled Ag/AgCl based ECG electrodes, PEDOT:PSS textile electrodes without the addition of ionic liquids and textile electrodes obtained with PEDOT:PSS added with 1-ethyl-3-methylimidazole ethylsulphate (FIG. 12). FIG. 12 clearly shows that the skin/electrode impedance obtained for the textile electrodes object of the present invention is significantly lower than that obtained with PEDOT:PSS textile electrodes produced according to the current state of the art. Furthermore, the impedance values for the textile electrodes of PEDOT:PSS with the addition of 1-ethyl-3-methylimidazole ethylsulphate are very similar to those of the pre-gelled commercial electrodes studied. Impedance spectra were recorded for all electrodes produced. FIG. 13 shows the impedance values recorded at 20 Hz for the PEDOT:PSS electrodes added with the various ionic liquids object of the invention and a pre-gelled Ag/AgCl electrode used as a comparison (Euro ECG Electrodes, FIAB, Vicchio Firenze). The 20 Hz value was chosen because it is close to the frequency used for acquiring ECG signals. The electrode prepared with 1-butyl-3-methylimidazolium bromide additive shows an impedance greater than 200 kΩ, which however is adequate for the acquisition of the ECG signal. FIG. 14 shows the ECG trace obtained with the electrode object of the invention in which the PEDOT:PSS was added with 1-ethyl-3-methylimidazole ethylsulphate. At the same time the tests carried out with electrodes prepared with PEDOT:PSS only did not show an response. ECG traces were recorded for each electrode object of the invention, and the noise index was calculated in accordance with the literature (Computers in Cardiology 2007; 34: 157-160). All the electrodes show a noise index lower than 0.1 highlighting a good signal quality and underlining how it is possible to use them to acquire ECG signals.

ECG Test (2)

[0113] A further test was carried out by directly printing the electrode on an adherent bioceramic mesh with an integrated compression band, positioning the electrodes in the same position as in the previous case, dry and in the absence of any preliminary skin treatment. Tests were performed on healthy volunteers in the presence of major (man) or minor (woman) compression of the electrode on the skin. The acquisition was carried out with a custom reading electronics based on the front-end for ECG and ADS1292R breath by Texas Instruments, with Bluetooth wireless transmission of the signal to a receiving device, in the absence of any analog or digital filter applied to the signal (raw data). Examples of signals acquired in different operating conditions are reported, so as to encourage the appearance of artifacts:

[0114] 1. FIG. 16: male subject, mild physical activity

[0115] 2. FIG. 17: male subject, intense physical activity

[0116] 3. FIG. 18: female subject, mild physical activity

[0117] 4. FIG. 19: female subject, transition to intense physical activity.

[0118] In all cases there is a perfectly clean signal, despite the absence of any form of filtering (note the presence of normal low frequency and high frequency artifacts, which otherwise would not be present).

Washability Tests

Washing Protocol

[0119] All the tests were carried out following a washing protocol similar to that of the reference standard ISO 105 C10: 2006. The fabric samples with the electrodes printed following the procedures indicated above are immersed in a 2.5 L beaker containing tap water and 20 grams of liquid detergent (Marseille for hand washing) at a temperature of about 40° C. They are subjected to a gentle stirring and a constant temperature for 30 minutes. Afterwards, the rinsing process takes place: water is poured with detergent and the beaker is filled with tap water at room temperature and stirred for 2 minutes. The electrodes are extracted and dried first with paper to remove excess water, then in an oven set at 60° C. for 35-40 minutes. This concludes a wash cycle.

Washing Test Example 1

[0120] A pair of electrodes was made on bioceramic fabric in the embodiment 1 described above, using 1-butyl methyl imidazolium acetate as the ionic liquid with the composition obtained as described in table 1. The pair of electrodes was characterized in terms of resistance, skin-electrode impedance and noise index in the electrocardiogram recording obtaining the following values 70.Math.Ω, 3.7Ω10.sup.4Ω and 0.013, respectively. The electrodes were subjected to 20 washing cycles and the resistance, electrode skin impedance and noise index in the recording of the electrocardiogram were measured every 5 washing cycles, showing good functioning up to the twentieth cycle. At the twentieth cycle the resistance was 2.4.Math.10.sup.2Ω and the skin electrode impedance was 3.4.Math.10.sup.5Ω. The noise index was 0.068, still sufficient to record a good ECG.

Washing Test Example 2

[0121] A pair of electrodes was made on bioceramic fabric in the embodiment 1 using 1-ethyl-3-methylimidazolium acetate as the ionic liquid with the composition obtained as described in table 1. The pair of electrodes was characterized in terms of resistance, skin electrode impedance and noise index in the recording of the electrocardiogram obtaining the following values 1.3.Math.10.sup.2Ω, 1.0.Math.10.sup.5Ω and 0.0176, respectively. The electrodes were subjected to 20 washing cycles and the resistance, electrode skin impedance and noise index in the recording of the electrocardiogram were measured every 5 washing cycles, showing good functioning up to the twentieth cycle. At the twentieth cycle the resistance was 1.7.Math.10.sup.2Ω and the electrode skin impedance was 1.5.Math.10.sup.6Ω. The noise index was 0.038, still sufficient to record a good ECG.

Washing Test Example 3

[0122] Different pairs of electrodes were made in the embodiment 1 using 1-butyl methyl imidazolium acetate as the ionic liquid with the composition obtained as described in table 1. The electrodes were deposited on PRO 29518, OPY 170, THINK 27749, STRATEGY RAW CUT, PRO 29374 and THINK OPACITY. The electrodes were subjected to 15 washing cycles and the ability to read the ECG signal was verified every 5 washing cycles. The electrodes obtained on each type of fabric maintained the ability to record the ECG signal for 15 washing cycles.

TABLE-US-00002 TABLE 2 Initial values Resistance Impedance Noise index Fabric (kΩ) Ω (20 Hz) (tot) PRO 29518 0.16 3.70 .Math. 10.sup.6 0.069108 OPY 170 0.18 5.18 .Math. 10.sup.5 0.026673 THINK 27749 0.084 2.43 .Math. 10.sup.5 0.019501 STRATEGY RAW CUT 0.3 9.28 .Math. 10.sup.4 0.025904 PRO 29374 0.1 1.75 .Math. 10.sup.5 0.016133 THINK OPACITY 0.08 1.21 .Math. 10.sup.5 0.01351 Values after 15 washing cycles Resistance Impedance Fabric (kΩ) Ω (20 Hz) NI m (tot) PRO 29518 0.22 1.71 .Math. 10.sup.5 0.03207 OPY 170 0.89 3.99 .Math. 10.sup.4 0.02112 THINK 27749 0.37 3.70 .Math. 10.sup.4 0.01627 STRATEGY RAW CUT 0.69 1.04 .Math. 10.sup.5 0.02915 PRO 29374 0.294 9.42 .Math. 10.sup.4 0.02074 THINK OPACITY 0.47 1.69 .Math. 10.sup.5 0.01524

Washing Test Example 4

[0123] A pair of electrodes was made on bioceramic fabric in the embodiment 1 using 1-butyl methyl imidazolium acetate as an ionic liquid with a obtained composition to which a crosslinker was added. The composition was prepared by starting by mixing 8.4 g of suspension of PEDOT:PSS PH 1000, 1.0 g of dimethyl sulphoxide, 0.10 g of 1-butyl methyl imidazolium and 0.5 g of 3-(glycidyloxypropyl) trimethoxy-silane. The electrodes were subjected to 25 washing cycles and the ability to read the ECG signal was verified every 5 washing cycles. At the twenty-fifth cycle the resistance was 1.0.Math.10.sup.3Ω and the skin electrode impedance was 3.9.Math.10.sup.4Ω. The noise index was 0.024, still sufficient to record a good ECG.

Breath Test

[0124] Through the same reading electronics, same setup, on a healthy volunteer in pedaling activity with increasing intensity, several breath and ECG signals were detected simultaneously, through the same textile electrodes. The result is shown in:

[0125] 1. FIG. 20: Subject who alternates breathing with apnea

[0126] 2. FIG. 21: Subject during moderate physical effort.

[0127] In all cases there is a perfectly clean signal, despite the absence of any form of filtering (note the presence of normal low frequency and high frequency artifacts, which otherwise would not be present).