Bionic embroidery electrocardio-electrode based on tree frog sole sucker structure

Abstract

The invention relates to the technical field of textile material medical supplies, in particular to a bionic embroidery electrocardio-electrode based on a tree frog sole sucker structure, which comprises conductive yarns, a base fabric and a liner, the base fabric and the liner are overlapped up and down to form an insulating layer; conducting layers are arranged on the front and back surfaces of the insulating layer; the conductive layer is formed by sewing conductive yarns on the front surface and the back surface of the insulating layer respectively through an embroidery process; a plurality of uniform and stable tiny hexagonal granular bulge units are distributed on the surface of the bionic embroidery electrocardio-electrode. Through the bionic suction cup structural design, the uniformity and interface friction force of the contact surface of the embroidery electrocardio-electrode and the skin are increased, the influence of the skin cuticle and dynamic displacement on the electrocardiosignal monitoring sensitivity and stability is effectively reduced, the skin anaphylaxis caused by a traditional Ag / AgCl gel wet electrode is avoided, and the embroidery electrocardio-electrode is easily integrated into a wearable intelligent garment and is convenient to use. The function of monitoring electrocardiosignals for a long time can be realized.

Description

Technical Field

[0001] The invention relates to the technical field of textile material medical supplies, and in particular to a bionic embroidery electrocardiogram electrode based on a tree frog foot suction cup structure. Background Art

[0002] Electrocardiogram (ECG) is the main way to detect cardiac electrical activity and a conventional means of predicting and diagnosing cardiovascular diseases. The traditional ECG system uses disposable Ag / AgCl gel wet electrodes, which can be used with conductive paste to infiltrate the skin stratum corneum, thereby reducing the influence of the stratum corneum on the skin-electrode interface impedance. However, the wet electrodes are easily dehydrated during use, resulting in reduced signal quality, and are also prone to skin itching and allergic reactions. The embroidered fabric dry electrodes do not require the use of adhesives such as gel, and have the characteristics of softness, skin-friendliness, breathability, moisture permeability, and reusability. The wire structure is not easy to loosen and deform, the preparation process is short, and it has good customizability, comfort and durability, and is easy to integrate into wearable smart clothing. However, in the process of using embroidered electrodes to monitor ECG signals for a long time, the continuous growth of the skin stratum corneum will cause the skin-electrode interface impedance to gradually increase, reducing the sensitivity of ECG signal acquisition; and because no adhesives such as gel are used, the embroidered electrodes are prone to displacement when the human body is in dynamic activities, reducing the stability of ECG signal acquisition. Therefore, it is necessary to research and develop embroidered ECG electrodes with good sensitivity and stability to meet the actual application needs in the medical field.

[0003] The surface morphology of many biological suckers in nature usually exhibits functions such as increasing friction and regulating the liquid environment. For example, the toe end of the tree frog's foot has a sucker structure with hexagonal columnar protrusion units, and there are grooves with a depth of 8 to 10 μm and a width of 1 to 5 μm between the units. The mucus secreted from the mucus gland pores on the tree frog's foot flows through the grooves between the units to facilitate the infiltration of the entire foot surface, forming a uniformly distributed mucus layer. Relying on the adhesion and friction generated by the foot sucker, the tree frog can climb freely on vertical walls and tree trunk surfaces. Its adhesion mechanism and structural characteristics provide a good reference for the improved design and development of embroidery ECG electrodes.

[0004] In recent years, there are few studies at home and abroad on the use of embroidery ECG electrode bionic suction cup structure design to reduce the impact of skin stratum corneum and dynamic displacement on ECG signal monitoring. Chinese patent (patent publication number: CN104523267A, publication date: April 22, 2015) "An embroidered fluffy flexible ECG electrode" discloses an ECG electrode that uses silver-plated conductive yarn to form a conductive fluff layer through an embroidery method, which overcomes the problem of reduced skin-electrode interface impedance performance due to stratum corneum growth during long-term wear, but still has the defect of poor electrode surface structure stability. Chinese patent (patent publication number: CN109730673A, publication date: May 10, 2019) "An embroidered physiological electrical signal monitoring electrode and its preparation method" discloses an electrode that uses carbon-based fiber-containing conductive yarn to sew on a substrate fabric through an embroidery process to form a conductive layer, which meets the medical in vitro material cytotoxicity test standards and has good biocompatibility, but still has the defect of poor signal monitoring sensitivity.

[0005] However, these disclosed technologies do not consider utilizing the bionic suction cup structure design of the embroidered ECG electrode to increase the uniformity and interface friction of the electrode-skin contact surface, reduce the influence of the skin stratum corneum and dynamic displacement on the monitoring signal, and thus improve the sensitivity and stability of the embroidered ECG electrode. Summary of the invention

[0006] The purpose of the present invention is to solve the shortcomings existing in the prior art, and to propose a bionic embroidery ECG electrode based on the suction cup structure of the tree frog's foot. By distributing tiny hexagonal granular protrusion units evenly and stably on the surface of the fabric, the interface friction force is large and the isotropy is good when it contacts the skin, thereby effectively improving the sensitivity and stability when monitoring ECG signals.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A bionic embroidery ECG electrode based on a tree frog foot suction cup structure comprises a conductive yarn, a base fabric and a pad; the base fabric and the pad are stacked up and down to form an insulating layer, and a conductive layer is arranged on both the front and back sides of the insulating layer; the conductive layer is formed by sewing the conductive yarn on the front and back sides of the insulating layer through an embroidery process;

[0009] The bionic embroidery ECG electrode imitates the microstructure of the suction cup on the surface of the tree frog's sole. A plurality of uniform and stable tiny hexagonal granular protrusion units are distributed on the surface of the bionic embroidery ECG electrode. The fabric surface has large friction and good isotropy.

[0010] Preferably, the conductive yarn is a nylon conductive yarn with a silver-plated surface; the conductive yarn has a silver fiber content of 15-20%, a linear density of 30-40 tex, a resistance of 2-5 Ω / cm, and a diameter of 0.1-0.2 mm.

[0011] Preferably, the base fabric is a polyester-viscose blended elastic knitted fabric with a gram weight of 250-270 g / m 2 , thickness is 1~1.1mm.

[0012] Preferably, the liner is a polyvinyl alcohol water-soluble non-woven fabric with a gram weight of 50 to 70 g / m 2 .

[0013] Preferably, the bionic embroidery ECG electrode is in the shape of a perfect circle, with a diameter of 20 to 30 mm and a total thickness of 1.5 to 2.0 mm.

[0014] Preferably, the stitch process parameters of the bionic embroidery ECG electrode are line spacing 0.2-0.3 mm, unit size 8*8-10*10 mm 2 , the number of stitches is 500 to 650.

[0015] Preferably, the groove formed between two adjacent hexagonal granular protrusion units has a depth of 0.5 to 0.6 mm and a width of 0.1 to 0.2 mm.

[0016] Preferably, the embroidery process is to embed the conductive yarn into the base fabric and the pad in the form of embroidery by an embroidery machine rather than using other embedding techniques.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The present invention imitates the suction cup microstructure on the surface of the tree frog's sole, and distributes evenly and stably tiny hexagonal granular protrusion units on the surface of the embroidered ECG electrode, so that the friction of the fabric surface is large and isotropy is good, which effectively reduces the influence of the skin stratum corneum and dynamic displacement on the monitoring signal, that is, reduces the skin-electrode interface impedance, ECG baseline drift amplitude and stabilization time, and increases the signal-to-noise ratio.

[0019] 2. Compared with traditional embroidery ECG electrodes, the present invention has better sensitivity and stability, skin-electrode interface impedance ≤48KΩ, signal-to-noise ratio ≥34dB, ECG baseline drift amplitude ≤0.1mV, baseline stabilization time ≤9s, and is more suitable for long-term ECG signal monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of the structure of a bionic embroidery ECG electrode provided in an embodiment of the present invention;

[0021] Figure 2A schematic diagram of the surface stitches of a bionic embroidery ECG electrode provided in an embodiment of the present invention;

[0022] Figure 3 Schematic diagram of stitch process parameters of the bionic embroidery ECG electrode provided in an embodiment of the present invention; (a) is the line spacing, and (b) is the unit size.

[0023] In the figure: 1. Conductive yarn, 2. Base fabric, 3. Pad. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings, so that those skilled in the art can better understand the advantages and features of the present invention, thereby making a clearer definition of the protection scope of the present invention. The embodiments described in the present invention are only a part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0025] like Figure 1 The schematic diagram of the longitudinal section structure of the embroidery ECG electrode shown is a bionic embroidery ECG electrode based on the suction cup structure of the tree frog's sole, comprising a conductive yarn 1, a base fabric 2 and a pad 3; the base fabric 2 and the pad 3 are stacked up and down to form an insulating layer, and a conductive layer is arranged on both the front and back sides of the insulating layer; the conductive layer is formed by sewing the conductive yarn 1 on the front and back sides of the insulating layer respectively through an embroidery process;

[0026] The bionic embroidery ECG electrode imitates the suction cup microstructure on the surface of the tree frog's sole. A plurality of uniform and stable tiny hexagonal granular protrusion units are distributed on the surface of the bionic embroidery ECG electrode, so that the friction force of the fabric surface is large and the isotropy is good.

[0027] Specifically, the conductive yarn 1 is a silver-plated nylon yarn with a silver fiber content of 18%, a line density of 36 tex, a resistance of 2.7 Ω / cm, and a diameter of 0.16 mm, and is used as both the upper thread and the lower thread of embroidery.

[0028] Specifically, the base fabric 2 is a polyester-viscose blended high-elastic knitted fabric with a gram weight of 270 g / m 2 The thickness is 1.05mm, and the elastic recovery rate in the warp and weft directions is 100%, which meets the elastic requirements of the electrode fitting the skin during ECG collection.

[0029] Specifically, the liner 3 is a polyvinyl alcohol water-soluble non-woven fabric with a gram weight of 60g / m 2 , which can improve the stability and smoothness of embroidery and increase the thickness of embroidery ECG electrodes.

[0030] Specifically, the embroidered ECG electrode is in the shape of a perfect circle, with a diameter of 26 mm and a total thickness of 1.6 mm.

[0031] Specifically, the surface stitches of the embroidery ECG electrode are uniformly distributed and stable tiny hexagonal granular protrusion units, and the stitch process parameters are line spacing 0.3mm and unit size 10*10mm. 2 , the number of stitches is 535.

[0032] Specifically, the groove formed between two adjacent hexagonal granular protrusion units has a depth of 0.6 mm and a width of 0.2 mm.

[0033] Specifically, the embroidery process refers to embedding the conductive yarn into the high-elastic knitted fabric in the form of embroidery through the Brother NV180 computer embroidery and sewing machine, rather than using other embedding technologies.

[0034] In practical application, the electrode pattern is designed by embroidery plate making software, and then input into the computer embroidery sewing machine to prepare the electrode by embroidery. On the polyester-viscose blended high-elastic knitted fabric base fabric, the conductive yarn repeatedly passes through the base fabric according to the design requirements, and the upper and lower surfaces are both conductive layers, and the middle is an insulating layer, thus forming a Figure 1 The multi-layer structure of the embroidery electrode is used to prepare a perfect circular embroidery ECG electrode sheet.

[0035] The embroidery process of the present invention is significantly different from the traditional fabric electrode preparation technology. For example, the non-woven electrodes based on polymer coating or printing have shortcomings such as poor elasticity and resistance that is easily affected by tensile deformation; the needle punching or hydroentanglement technology randomly embeds the conductive yarn into the base fabric, which is highly destructive to the base fabric; the coil structure of the knitted electrode is prone to loose deformation, resulting in noise when monitoring ECG signals. In comparison, the preparation process of the embroidery electrode of the present invention is short, has good customizability, comfort and durability, and is easy to integrate into wearable smart clothing.

[0036] The skin-electrode interface impedance test of the embodiment of the present invention is specifically performed according to the following operating steps:

[0037] A conventional medical disposable Ag / AgCl gel wet electrode was used as the reference electrode. A skin-electrode model was established using the reference measurement method. A multimeter was used to measure the impedance values ​​and the skin-electrode interface impedance was calculated indirectly.

[0038] d1=d2=6cm, indicating the distances between the center points A and B of the gel electrodes and the center point C of the embroidery electrode respectively; R1 is the impedance between gel electrode No. 1 and the embroidery electrode; R2 is the impedance between gel electrode No. 2 and the embroidery electrode; R3 is the impedance between the two gel electrodes.

[0039] The skin-electrode interface impedance is: R = R1-R3 / 2 = R2-R3 / 2.

[0040] The skin-electrode interface impedance of the disposable Ag / AgCl gel electrode control group obtained in the embodiment of the present invention is 320KΩ, the impedance of the commonly used satin stitch embroidery ECG electrode is 225KΩ, and the impedance of the bionic embroidery ECG electrode is 48KΩ, and the impedance performance is much better than that of the disposable Ag / AgCl gel electrode and the satin stitch embroidery ECG electrode. The thickness of the stratum corneum on the surface of human skin is 0.1-0.2mm. The grooves formed between the tiny hexagonal granular bionic protrusion units of the present invention have a depth of 0.6mm and a width of 0.2mm, which can effectively reduce the negative impact of the growth of the skin stratum corneum on the skin-electrode interface impedance and improve the sensitivity of monitoring ECG signals.

[0041] The human body electrocardiogram signal acquisition test of the embodiment of the present invention is specifically performed according to the following operation steps:

[0042] Use silver-plated copper wire to dip into 8813XG quick-drying conductive silver glue and assemble it on the embroidery electrode with conductive double-sided tape. After the conductive silver glue is cured, use medical tape to attach the embroidery ECG electrode to the human body.

[0043] Embroidered ECG electrodes were attached to the left and right wrists of the subjects, and the right calf was connected to the ground electrode of the multi-channel physiological signal acquisition system. The three electrodes formed a single lead system in the human body, and the difference in potential between the two upper limbs was measured to monitor the ECG signals. The measurement of the electrode attached to the radial artery of the wrist was taken as the ECG signal group, and the area above the radial artery covered by the muscle of the forearm was taken as the epidermal noise group, and the obtained data were calculated.

[0044] Signal-to-noise ratio (SNR) refers to the ratio between signal and noise in an electronic system, reflecting the clarity and accuracy of the signal. The definition formula of SNR is SNR = 10log (S / N), where S and N are the average power of the signal and the average power of the noise, respectively. The SNR of the embroidery ECG electrode is obtained by converting them:

[0045]

[0046] Where: μp is the average pulse amplitude, mV; σp is the pulse fluctuation level; A is the total number of pulses; i is the number of cycles; P i is the pulse amplitude for each cycle, mV; μ n is the average noise amplitude, mV; σ n is the noise fluctuation level, N i is the noise amplitude per cycle, mV.

[0047] Baseline drift refers to the phenomenon that the ECG baseline level is unstable or drifts. During the signal acquisition process, when an extremely low-frequency curve is superimposed on the original signal, it will cause the original signal to fluctuate slowly and slightly. This drift trend will damage the accuracy of the original signal acquisition, thereby affecting the results of subsequent data processing. Baseline drift amplitude V p The smaller it is, the more stable the sensing performance of the electrode is.

[0048] The ECG baseline drift amplitude calculation formula is:

[0049] V p =|V i -V0|

[0050] Where: V1 is the maximum amplitude after the baseline is stable, mV; V0 is the maximum amplitude of the initial state signal, mV.

[0051] The baseline stabilization time refers to the time required for the ECG baseline to reach a stable state. The shorter the baseline stabilization time Tp, the better the electrode's response sensitivity to the signal.

[0052] The ECG baseline stabilization time calculation formula is:

[0053] T p =|T1-T0|

[0054] Where: T1 is the moment when the ECG waveform reaches stability, s; T0 is the initial moment of the test, s.

[0055] The SNR of the disposable Ag / AgCl gel electrode control group obtained in the embodiment of the present invention is 25.5dB, the ECG baseline drift amplitude is 0.2mV, and the ECG baseline stabilization time is 9.8s; the SNR of the commonly used satin stitch embroidery ECG electrode is 30.1dB, the ECG baseline drift amplitude is 0.3mV, and the ECG baseline stabilization time is 13.8s; and the SNR of the bionic embroidery ECG electrode is 34.2dB, the ECG baseline drift amplitude is 0.1mV, and the ECG baseline stabilization time is 8.2s. The sensitivity and stability of its ECG signal monitoring are better than those of the disposable Ag / AgCl gel electrode and the satin stitch embroidery ECG electrode.

[0056] Compared with the commonly used satin stitch embroidery ECG electrode, the bionic embroidery ECG electrode obtained in the embodiment of the present invention has a tighter structure between the threads, a more even distribution of the embroidery threads, and a more stable conductive path with good isotropy. The grooves formed between the tiny hexagonal granular bionic protrusion units on the surface of the bionic embroidery ECG electrode have a depth of 0.6 mm and a width of 0.2 mm. During the long-term monitoring of ECG signals, a mixture of the skin stratum corneum, sweat, etc. forms a medium with a certain viscosity, which flows through the grooves and infiltrates the entire electrode surface, and is also conducive to discharging the sweat accumulated at the contact interface to the outside of the interface. This special structure increases the uniformity and friction of the contact interface between the electrode and the skin, reduces the displacement of the electrode when the human body is performing dynamic activities, and thus improves the sensitivity and stability of ECG signal monitoring.

[0057] In summary, the present invention imitates the suction cup microstructure on the surface of the tree frog's sole, and distributes tiny hexagonal granular protrusion units evenly and stably on the surface of the embroidered ECG electrode, so that the friction of the fabric surface is large and the isotropy is good, which effectively reduces the influence of the skin stratum corneum and dynamic displacement on the monitoring signal, that is, reduces the skin-electrode interface impedance, the ECG baseline drift amplitude and the time required for stabilization, and increases the signal-to-noise ratio.

[0058] The description and practice disclosed in the present invention are easy to think and understand for ordinary technicians in the technical field, and several improvements and modifications can be made without departing from the principles of the present invention. Therefore, modifications or improvements made without departing from the spirit of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A bionic embroidery ECG electrode based on the suction cup structure of the tree frog's foot, characterized in that: It comprises a conductive yarn, a base fabric and a pad; the base fabric and the pad are stacked up and down to form an insulating layer, and a conductive layer is arranged on both the front and back sides of the insulating layer; the conductive layer is formed by sewing the conductive yarn on the front and back sides of the insulating layer respectively through an embroidery process; The bionic embroidery ECG electrode imitates the microstructure of the suction cup on the surface of the sole of the tree frog, and a plurality of uniform and stable hexagonal granular protrusion units are distributed on the surface of the bionic embroidery ECG electrode.

2. The bionic embroidery ECG electrode based on the tree frog foot suction cup structure according to claim 1 is characterized in that: The conductive yarn is a nylon conductive yarn with a silver-plated surface; the silver fiber content of the conductive yarn is 15-20%, the line density is 30-40 tex, the resistance is 2-5Ω / cm, and the diameter is 0.1-0.2mm.

3. The bionic embroidery ECG electrode based on the tree frog foot suction cup structure according to claim 1, characterized in that: The base fabric is a polyester-viscose blended elastic knitted fabric with a gram weight of 250-270 g / m 2 , thickness is 1~1.1mm.

4. The bionic embroidery ECG electrode based on the tree frog foot suction cup structure according to claim 1, characterized in that: The liner is a polyvinyl alcohol water-soluble non-woven fabric with a gram weight of 50 to 70 g / m 2 .

5. The bionic embroidery ECG electrode based on the tree frog foot suction cup structure according to claim 1, characterized in that: The bionic embroidery ECG electrode is in the shape of a perfect circle, with a diameter of 20 to 30 mm and a total thickness of 1.5 to 2.0 mm.

6. The bionic embroidery ECG electrode based on the tree frog foot suction cup structure according to claim 1, characterized in that: The stitch process parameters of the bionic embroidery ECG electrode are line spacing 0.2-0.3 mm, unit size 8*8-10*10 mm 2 , the number of stitches is 500 to 650.

7. The bionic embroidery ECG electrode based on the tree frog foot suction cup structure according to claim 1, characterized in that: The groove formed between two adjacent hexagonal granular protrusion units has a depth of 0.5 to 0.6 mm and a width of 0.1 to 0.2 mm.

8. The bionic embroidery ECG electrode based on the tree frog foot suction cup structure according to claim 1, characterized in that: The embroidery process is that the conductive yarn is embedded into the base fabric and the pad in the form of embroidery by an embroidery machine.

Images