A dual-channel fabric electrode

Abstract

The present invention discloses a dual-channel fabric electrode, belonging to the field of flexible electronic devices. In order to solve the technical contradiction between the contact comfort of the existing electrode and the signal acquisition sensitivity, the technical solution is to design a dual-channel fabric electrode for resistance sensing and capacitance sensing. Two capacitance sensing channels are formed between the long pile regions and the short pile regions of the upper and lower composite fabrics. The conductive pile layer of the composite fabric in contact with the skin extends from one conductive region to the other conductive region to form a contact conductive pile layer, serving as a resistance sensing channel. The dual-channel fabric electrode of the present invention can collect bioelectric signals in real-time in multiple channels, has good conductivity, good sensitivity and high accuracy. At the same time, the electrode has strong contact comfort with the skin and is suitable for long-term use.

Description

Technical Field

[0001] The present invention belongs to the field of flexible electronic devices, and particularly relates to a fabric electrode. Background Art

[0002] Bioelectricity refers to the potential and polarity changes that occur in the organs, tissues, and cells of organisms during their life activities. The heartbeat, respiration, movement, etc. of the human body all leave traces of bioelectricity. Flexible electronic devices can monitor the bioelectric signals of the human body in real time by integrating different sensors. By comparing the bioelectric images and data in healthy and diseased states, abnormal information in the body can be detected early. However, the bioelectric signals of the human body are weak, vulnerable to interference, and difficult to collect.

[0003] Traditional electrodes for collecting bioelectric signals are divided into dry electrodes and wet electrodes. Wet electrodes mostly use disposable gel electrode patches, which improve the contact impedance at the skin-electrode interface and have good conductivity. However, over time, the conductive gel dries out, the contact impedance increases, and the collected signal decreases. In addition, the contact between the conductive gel and the skin easily causes problems such as skin redness, itching, and allergies, and long-term monitoring of surface electromyogram signals cannot be performed. Dry electrodes are divided into metal dry electrodes and flexible dry electrodes. Metal dry electrodes have no conductive gel, have poor adhesion to the skin, are prone to artifact phenomena, and the signal collection quality decreases. The manufacturing process of flexible dry electrodes is complex and costly. Flexible fabric electrodes have good comfort and can contact the skin well, but their conductivity is insufficient. Currently, the proposed flexible fabric electrodes have a single structure, mostly square, circular, triangular, etc. The invention patent CN104523267A discloses an embroidered fluff flexible electrocardiogram electrode. This electrode forms a "brush" structure by multiple fluff, which can achieve a signal transmission channel through multi-point contact with the skin. When producing the electrode, the method of cutting the conductive yarn is used to form multiple fluff. However, in order to ensure that the fluff is perpendicular to the fabric surface, the selected conductive yarn has a large bending stiffness and causes a certain degree of pain when contacting the skin. Summary of the Invention

[0004] Aiming at the technical contradiction between the contact comfort of existing electrodes and the sensitivity of signal collection, the present invention provides a fabric electrode capable of collecting bioelectric signals in real time with multiple channels, having good conductivity, good sensitivity, and high accuracy. At the same time, this electrode has strong contact comfort with the skin and is suitable for long-term use.

[0005] To achieve the above object, the present invention adopts the following technical solutions: A dual-channel fabric electrode, the fabric electrode is composed of two vertically symmetric composite fabrics and an elastic layer that forms a spatial interval between the two vertically symmetric composite fabrics. The composite fabric includes a fabric layer, and also includes conductive regions and non-conductive regions symmetrically distributed on the front and back sides of the fabric layer. And the conductive regions on the front and back sides of the fabric layer are connected, and a conductive fluff layer is provided on the conductive region on one side of the fabric layer. The conductive fluff layer includes a long fluff region and a short fluff region, and a non-conductive region is spaced between the long fluff region and the short fluff region. The fabric electrode further includes a contact conductive fluff layer that extends from the conductive fluff layer in contact with the skin composite fabric from one conductive region to the other conductive region.

[0006] Further, both ends of the elastic layer are connected to the two vertically symmetric non-conductive regions, and the elastic layer keeps the two vertically symmetric conductive fluff layers in a spatially separated state.

[0007] Further, the conductive region is a conductive pattern formed by embroidering conductive yarns through an embroidery process into the fabric layer and respectively embroidering on the front and back two sides of the fabric layer.

[0008] Further, the conductive fluff layer is multiple contacting and upright fluff.

[0009] Further, the conductive region is two columns of parallel and spaced conductive stripes, and the region outside the two columns of conductive stripes is the non-conductive region. The long fluff region is provided on one column of the conductive stripes, and the short fluff region is provided on the other column of the conductive stripes.

[0010] Further, the interval between the long fluff region and the short fluff region is 2 mm, the width of the long fluff region is 5 - 7 mm, the fluff height is 1 - 2 mm, the width of the short fluff region is 5 - 7 mm, the fluff height is 0.5 - 1 mm, the fluff height ratio of the long fluff region to the short fluff region is 2:1, and the fluff height of the contact conductive fluff layer is 0.2 mm.

[0011] Further, the fabric layer is an elastic plain weave fabric.

[0012] Further, the material of the elastic layer is one of polyurethane sponge, elastic non-woven felt, and elastic spacer fabric.

[0013] Further, the material of the conductive fluff layer is graphene fiber.

[0014] Compared with the prior art, the beneficial effects of the present invention:

[0015] (1) Compared with metal electrodes, the electrodes designed by the present invention are highly flexible and do not require conductive gel, so they can maintain good contact with the skin for a long time. The conductive fleece layer is connected to the conductive area, so that the fabric electrode has good conductivity. The manufacturing method is simple, overcoming the shortcomings of traditional flexible electrodes, such as insufficient conductivity and complex process.

[0016] (2) The dual-channel fabric electrode of the present invention has high sensitivity and accuracy while ensuring the comfort of contact with human skin. The present invention forms a contact conductive fleece layer by extending the conductive area on one side from the conductive area on the other side. The contact conductive fleece layer uses ultra-fine graphene fiber fleece, which can directly contact the skin and has good conductivity and comfort. While reducing the contact impedance between the skin and the electrode surface, it can avoid the itching sensation on the skin caused by using ordinary conductive yarns with large bending stiffness.

[0017] (3) The dual-channel fabric electrode of the present invention has dual sensing channels of resistance sensing and capacitance sensing. The resistance sensing channel is realized by contacting the conductive fleece layer. The body's bioelectrical signals flow through or move, causing the change in the resistance of the contact conductive fleece layer to reflect the health and exercise status of the human body. The electrode is used as a pressure sensor. The capacitance sensing channel is realized by the upper and lower conductive fleece layers, specifically by a plurality of mutually parallel and upright conductive fiber fleeces spaced between the upper and lower conductive fleece layers, which can actually be equivalent to a capacitor plate formed by a plurality of small capacitors connected in series. The single capacitance value changes slightly, but the total capacitance value changes significantly, which can improve the accuracy of recognition. The fleece is equivalent to human sweat hair, which can be sensitive to changes in muscle groups and improve detection accuracy. At the same time, the conductive fleece layer designed by the present invention includes a long-pile area and a short-pile area. The upper and lower long-pile areas and the space intervals therebetween and the upper and lower short-pile areas and the space intervals therebetween constitute two parallel capacitor cavities. The bioelectric current is charged and discharged through the capacitor cavity, causing the two capacitance values ​​of the conductive fleece layer to change. When the electrode is greatly affected by the deformation force, the upper and lower contacts of the long-pile area cause a short circuit, and the capacitance sensing of the short-pile area can still work.

[0018] (4) The dual-channel fabric electrode of the present invention can be equivalent to a first-order RC filter circuit, the contact conductive fleece layer is equivalent to a resistor R, and the upper and lower conductive fleece layers are equivalent to capacitors C. The present invention can be equivalent to two first-order RC filter circuits in parallel, and the capacitance value can be changed by adjusting the length of the graphene fiber to filter out interference signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the overall structure of the dual-channel fabric electrode of the present invention;

[0020] Figure 2 A side view of the dual channel fabric of the present invention;

[0021] Figure 3Top view of the conductive velvet layer of the dual-channel fabric of the present invention;

[0022] Figure 4 Equivalent circuit diagram of the dual-channel fabric electrode of the present invention;

[0023] Among them, 1 is a composite fabric, 2 is an elastic layer, 11 is a fabric layer, 12 is a conductive area, 13 is a non-conductive area, 14 is a conductive velvet layer, 15 is a contact conductive velvet layer, 16 is the skin, 17 is a conductive lead end, A is a long velvet area, B is a short velvet area, and a is a conductive yarn. Detailed implementation mode

[0024] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0025] A dual-channel fabric electrode of the present invention is square, with a length of 20 mm, a width of 20 mm, and a total thickness of less than 5 mm. The overall structure of the dual-channel fabric electrode is as shown in Figure 1 , Figure 2 and Figure 3 . The fabric electrode is composed of two symmetrically arranged upper and lower composite fabrics 1 and a conductive elastic layer 2 that forms a spatial interval between the two symmetrically arranged upper and lower composite fabrics 1. The composite fabric 1 includes a fabric layer 11, and also includes conductive areas 12 and non-conductive areas 13 symmetrically distributed on the front and back sides of the fabric layer 11. The conductive areas 12 on the front and back sides of the fabric layer are connected, and a conductive velvet layer 14 is provided on the conductive area A on one side of the fabric layer. The conductive velvet layer 14 includes a long velvet area A and a short velvet area B, and the long velvet area A and the short velvet area B are separated by a non-conductive area 13. The fabric electrode further includes a contact conductive velvet layer 15 formed by extending the conductive velvet layer in contact with the skin from one conductive area to the other conductive area.

[0026] In order to maintain the stability of the interface capacitance topology structure, as shown in Figure 1 , both ends of the elastic layer are connected to the two symmetrically arranged upper and lower non-conductive areas 13, and the elastic layer 2 keeps the two symmetrically arranged upper and lower conductive velvet layers 14 in a spatially separated state. The material of the elastic layer 2 is one of polyurethane sponge, elastic non-woven fabric, and elastic spacer fabric. The elastic layer 2 plays a role in forming a spatial interval between the two symmetrically arranged upper and lower composite fabrics 1, and constitutes a complete fabric electrode.

[0027] The fabric layer 11 serves as the base of the fabric electrode of the present invention and plays a role in supporting the entire electrode structure. It cannot be too soft, and at the same time, it is required to have good skin adhesion, sweat absorption and breathability. The fabric layer 11 of the present invention is an elastic plain fabric, and the material is 73% cotton fiber, 21% polyester fiber, 5% diene elastic fiber, and 1% spandex.

[0028] The conductive region 12 is a conductive pattern formed by threading the conductive yarn a through the fabric layer 11 by an embroidery process and embroidering it on the front and back surfaces of the fabric layer 11 respectively. As shown in Figure 1 the partial view circled in can be seen, the conductive yarn a forms a continuous pattern on the fabric layer 11. As shown in Figure 2 it can be seen that the conductive yarn a passes from one side of the fabric layer 11 to the other side, forming conductive regions 12 on the front and back surfaces of the fabric layer respectively, and the fabric layer 11 without the conductive yarn a constitutes a non-conductive region 13. The embroidery process of the present invention includes embedding the conductive yarn into the elastic plain weave fabric by the straight embroidery stitch. The conductive yarn is a polyester conductive yarn with a silver-plated surface, with a diameter of 0.045 mm and a resistivity in the range of 15 Ω / cm to 18 Ω / cm, having good electrical conductivity. Since the silver-plated conductive yarn also has antibacterial properties, it is commonly used in the textile field and can be in long-term contact with the skin. The contact conductive velvet layer 15 is affected by bioelectricity and deformation force, and its resistance value changes, serving as the resistive switching channel of the electrode.

[0029] In order to further improve the sensitivity of the fabric electrode, as shown in Figure 3As shown, fluff is adhered to the conductive area 12 on one side to form a conductive fleece layer 14, and the conductive fleece layer 14 is a plurality of contacting and upright fluffs. Preferably, the fluff material of the conductive fleece layer of the present invention is graphene fiber. The graphene fiber is purchased from Shandong Ao Rong Garment Co., Ltd., and the graphene fiber is cut into fluffs of different lengths using a fleece cutting machine. Graphene fiber has good conductivity, and the fluffs in contact with each other have the characteristic of like charges repelling each other after being charged, so that the fluffs are mutually opposed and supported, and can remain upright, which can simulate the sensitive perception of human sweat hair to changes in muscle groups, reduce the contact impedance between the skin and the electrode, and improve the sensitivity of the electrode. As a preferred embodiment, the graphene fiber fluff is formed into a conductive fleece layer by an electrostatic flocking method. The electrostatic flocking method uses the principle that like charges repel each other and opposite charges attract each other, so that the graphene fiber fluff is negatively charged. When the substrate is placed under grounding conditions, the graphene fluff is attracted by the substrate and accelerates to rise vertically to the surface of the substrate. By providing an adhesive on the surface of the substrate, the graphene fluff is vertically adhered to the substrate. In the process of electrostatic flocking, the present invention provides an adhesive layer between the conductive area 12 and the conductive fleece layer 14. The adhesive layer uses a removable adhesive. The adhesive is a polyacrylate adhesive with a viscosity of about 40000mPa·s, so that the conductive area 12 and the conductive fleece layer 14 can be well bonded. The embroidery method of direct embroidery is adopted, and the stitches are neat and uniform. The silver-plated conductive thread floats on the surface of the plain elastic fabric, and the graphene fiber is kept upright by the electrostatic flocking technology. Therefore, each graphene fiber fluff is vertically and firmly inserted between the single fibers of the silver-plated conductive thread to form a connection between the conductive area 12 and the conductive fleece layer 14. For graphene fiber, as an implementation method, the graphene fiber adopts sea-island graphene fiber, and its preparation method is to prepare graphene masterbatch by esterification polymerization of graphene material, blend and melt to obtain graphene polyester, use graphene polyester as island component, soluble polyester as sea component, obtain graphene sea-island raw silk by composite spinning method after melt blending, and then obtain sea-island graphene fiber by bundling, drawing, shaping, cutting and other processes, and remove the "sea" component by organic solvent to obtain ultrafine graphene fiber. The present invention adopts sea-island graphene fiber, combines electrostatic flocking process, forms extended fluff extending from one conductive area to another conductive area, and then treats the extended fluff with organic solvent to form ultrafine graphene fiber fluff, which is the contact conductive fleece layer 15. The ultrafine graphene fiber fluff can directly contact with the skin, has good conductivity and comfort, and can avoid the itching sensation on the skin caused by using ordinary conductive yarn with large bending stiffness while reducing the contact impedance between the skin and the electrode surface.

[0030] As an implementation method, Figure 3As shown, the conductive region 12 is two columns of parallel and spaced conductive stripes, and the region outside the two columns of conductive stripes is the non-conductive region 13. The long plush region A is provided on one column of the conductive stripes, and the short plush region B is provided on the other column of the conductive stripes. The interval between the long plush region and the short plush region is 2 mm. The width of the long plush region is 5 - 7 mm, the height of the plush is 1 - 2 mm. The width of the short plush region is 5 - 7 mm, the height of the plush is 0.5 - 1 mm. The ratio of the plush height of the long plush region to that of the short plush region is 2:1. The height of the plush of the contact conductive plush layer is 0.2 mm.

[0031] As Figure 1 shown, the space interval between the upper and lower composite fabrics 1 forms an air insulator. The upper and lower conductive plush layers 14 and the space interval therebetween are equivalent to a capacitor. When the bio-current charges and discharges through the capacitor cavity, the capacitance value changes, serving as the capacitance change channel of this electrode. From Figure 2 and Figure 4 shown, the capacitance distances between the upper and lower long plush regions A and between the upper and lower short plush regions B are different, forming two kinds of capacitors in the fabric electrode. Specifically, the upper and lower long plush regions A and the space interval therebetween form the first capacitor cavity C1, and the upper and lower short plush regions B and the space interval therebetween form the second capacitor cavity C2. The fabric electrode of the present invention has two capacitor cavities, and the capacitance value changes of the two capacitors are different under the influence of bio-electricity and deformation force. When the human body applies a large force, the upper and lower long plush regions A may come into contact, but there can still be a space interval between the upper and lower short plush regions B, and the capacitance characteristics can be maintained well.

[0032] The preparation method of the fabric electrode of the present invention includes the following steps: Step 1, use a flocking machine to make graphene plush into long and short plush; Step 2, adopt an embroidery method to form a conductive pattern on the upper and lower surfaces of an elastic plain weave fabric with silver-plated conductive yarns to form a conductive region and a non-conductive region; Step 3, thinly coat an adhesive layer on the conductive region on one side of the fabric to form an adhesive layer, and plant the graphene plush in Step 1 on the adhesive by means of electrostatic flocking and embed it into the fine pores on the surface of the elastic plain weave fabric. The long plush region and the short plush region are arranged at intervals to obtain a composite fabric; Step 4, cure and remove the glue from the adhesive layer in Step 3, and remove the floating fluff of the graphene plush on the surface of the composite fabric; Step 5, use an elastic layer as a support, and symmetrically place two composite fabrics up and down to form a double-channel fabric electrode. Step 3 also includes extending the graphene plush of one composite fabric from one side of the conductive region to the other side of the conductive region to form a contact conductive plush layer 15, and the contact conductive plush layer 15 is used as the side in direct contact with the skin.

[0033] The double-channel fabric electrode structure of the present invention has a double-sensing channel of resistance sensing and capacitance sensing. AsFigure 4 As shown, when real-time monitoring of bioelectrical signals, the contact conductive velvet layer 15 of the dual-channel fabric electrode is in contact with the human skin 16, and the other end of the dual-channel fabric electrode is connected to the conductive lead end 17. The human condition is judged through the dual-sensing channels of resistance sensing and capacitance sensing. The resistance sensing is realized by the contact conductive velvet layer 15. The body bioelectrical signal flowing through or movement causes a change in the resistance of the contact conductive velvet layer to reflect the health and movement state of the human body. The fabric electrode is used as a pressure sensor. Wear two dual-channel fabric electrodes of the present invention at the position of the human skin muscle group, record the change in the differential resistance value of the two fabric electrodes, and connect the conductive lead ends 17 of the two dual-channel fabric electrodes. The capacitance sensing is realized by the capacitance cavity formed by the upper and lower conductive velvet layers 14 of the fabric electrode. Specifically in use, the integration of the electrode and the myoelectric sensor can be used for gesture recognition. For example, during the execution of the "fist clenching" movement, when the fist clenching amplitude is small, the deformation amount on the skin surface is small. For resistance sensing, the differential movement resistance value decreases slightly; for capacitance sensing, since the surface electromyogram signal is a very weak alternating voltage signal, the capacitance value is mainly affected by the charge quantity, and the capacitance value becomes larger. When the fist clenching amplitude is large, the deformation amount on the skin surface is large. For resistance sensing, the differential movement resistance value decreases significantly; for capacitance sensing, it is easy to lose the spatial interval between the upper and lower long velvet regions A, resulting in a short circuit of the first capacitance cavity C1. However, the long velvet region and the short velvet region of the electrode are separately arranged, and the second capacitance cavity C2 formed by the upper and lower short velvet regions B and the spatial interval between them can still work effectively. At this time, the capacitance is affected by the spacing, and the capacitance value becomes larger.

[0034] As Figure 4 shown, for the fabric electrode structure designed by the present invention, the contact conductive velvet layer is equivalent to a resistor R, and the upper and lower conductive velvet layers 14 are equivalent to capacitors. This electrode structure can be equivalent to two first-order RC filter circuits connected in parallel. By adjusting the length of the graphene fiber, the capacitance value can be changed to filter out interference signals, simplifying the design of the filter circuit in the bioelectrical acquisition circuit, as Figure 4 shown in the equivalent circuit diagram pointed by the arrow in the figure. This dual-channel fabric electrode can be reused, has good conductivity, sensitivity and comfort, and is very suitable for the monitoring and recognition of weak electrical signals such as bioelectrical signals.

Claims

1. A dual-channel fabric electrode, characterized in that, The fabric electrode is composed of two vertically symmetrical composite fabrics and an elastic layer that forms a spatial interval between the two vertically symmetrical composite fabrics. The composite fabric includes a fabric layer, and also includes conductive regions and non-conductive regions symmetrically distributed on the front and back sides of the fabric layer. The conductive regions on the front and back sides of the fabric layer are connected. In addition, there is a conductive velvet layer provided on the conductive region on one side of the fabric layer. The conductive velvet layer includes a long velvet region and a short velvet region, and a non-conductive region is spaced between the long velvet region and the short velvet region. The fabric electrode further includes a contact conductive velvet layer formed by the conductive velvet layer in contact with the skin contacting the composite fabric extending from the conductive region on one side to the conductive region on the other side; Both ends of the elastic layer are connected to the two vertically symmetrical non-conductive regions, and the elastic layer keeps the two vertically symmetrical conductive velvet layers in a spatially separated state; The conductive regions are two rows of parallel and spaced conductive stripes, and the regions outside the two rows of conductive stripes are the non-conductive regions. The long velvet region is provided on one row of the conductive stripes, and the short velvet region is provided on the other row of the conductive stripes.

2. The dual-channel fabric electrode according to claim 1, characterized in that, The conductive regions are conductive patterns formed by embroidering conductive yarns into the fabric layer through an embroidery process and respectively embroidering them on the front and back surfaces of the fabric layer.

3. The dual-channel fabric electrode according to claim 1, characterized in that The conductive velvet layer is multiple upright and contacting villi.

4. The dual-channel fabric electrode according to claim 1, wherein The interval between the long velvet region and the short velvet region is 2 mm. The width of the long velvet region is 5 - 7 mm, the height of the villi is 1 - 2 mm. The width of the short velvet region is 5 - 7 mm, the height of the villi is 0.5 - 1 mm. The ratio of the villi height of the long velvet region to the short velvet region is 2:

1. The height of the villi of the contact conductive velvet layer is 0.2 mm.

5. The dual-channel fabric electrode according to claim 1, wherein The fabric layer is an elastic plain fabric.

6. The dual-channel fabric electrode according to claim 1, characterized in that, The material of the elastic layer is one of polyurethane sponge, elastic non-woven felt, and elastic spacer fabric.

7. The dual-channel fabric electrode according to claim 1, wherein The material of the conductive velvet layer is graphene fiber.

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