CN112545454A

CN112545454A - Sweat detection sensing device and sweat amount detection method

Info

Publication number: CN112545454A
Application number: CN202011206899.4A
Authority: CN
Inventors: 许太林; 张学记; 颜丹; 李冠华
Original assignee: Shenzhen Refresh Intelligent Technology Co ltd
Current assignee: Shenzhen Refresh Intelligent Technology Co ltd
Priority date: 2020-11-03
Filing date: 2020-11-03
Publication date: 2021-03-26

Abstract

The application discloses a sweat detection sensing device and a sweat amount detection method. The sweat detection sensing device includes: a water-absorbent swelling member; and a fabric wire rod arranged on the water absorption swelling component, wherein the surface of the fabric wire rod is provided with a conductive coating layer, and the fabric wire rod can deform in the length direction of the fabric wire rod under the water absorption swelling of the water absorption swelling sheet, so that the conductive coating layer can follow the deformation to cause resistance change. This application sweat detects sensing device absorbs the sweat and swells the emergence volume through the swelling subassembly that absorbs water, and the fabric wire rod produces the resistance change because of deformation brings under this swelling to turn into the volume of sweating volume into the resistance change rate that can observe reading, have like this better ability and detect out the sweating volume comparatively conveniently, and it is lower to detect out the limit.

Description

Sweat detection sensing device and sweat amount detection method

Technical Field

The invention relates to the technical field of biosensors, in particular to a sweat detection sensing device and a sweat amount detection method.

Background

The human body sweat mainly comprises 98-99% of water (pH value is 4.2-7.5), sodium chloride (about 300mg/100mL), and 1-2% of other substances (including a small amount of urea, lactic acid, fatty acid, glucose and the like).

When a human body is doing exercise or working in a high temperature environment, a large amount of sweat can flow out. When a patient is rescued, the fluid infusion amount is required to be input according to the sweating amount of the patient so as to prevent the patient from suffering from life failure. When Na + is less than 58.4mg, K + is less than 10mg and Cl-is less than 45.4mg in each liter of sweat, a series of problems will occur to a human body, so that the human body is obviously allergic to the stimulation of sight and hearing, the regulating capacity of the antibody of the body is reduced, and symptoms such as muscle spasm, dehydration, even coma and the like can occur.

If the sweat amount in these human sweat can in time be surveyed, then can in time give people the early warning to can effectively carry out the salt and water supply, avoid the harm that the excessive sweat amount led to the fact normal vital sign.

Disclosure of Invention

In order to solve the above problems, the present application provides a sweat detection sensing device and a sweat amount detection method, which can conveniently detect the sweat amount and have a low detection limit.

According to one aspect of the present application, a sweat detection sensing device comprises:

a water-absorbent swelling member;

and a fabric wire disposed on the water-absorbing swelling member and having a conductive coating layer on a surface thereof, wherein the fabric wire is capable of deforming in a length direction thereof when the water-absorbing swelling member swells upon absorbing water, so that the conductive coating layer causes a resistance change following the deformation.

The detection principle of the sweat detection sensing device is simply to convert the volume of the sweat amount into a resistance change rate which can be observed and read. The specific process is as follows: the water absorption swelling component can absorb sweat and swell. Swelling of the water-swellable component results in a significant increase in volume. Although the swelling of the water-swellable component is multidirectional, the swelling of the water-swellable component eventually deforms by significant "pulling" in the lengthwise direction of the fabric strands due to the "one-dimensional nature" of the fabric strands. Under this deformation, deformation is followed to conductive coating in this direction, and easy understanding is that conductive coating follows deformation in that wire rod length direction takes place, is similar to "stretched out the face" effect, brings its slight sectional area to a certain extent and diminishes and slight length increase, finally makes resistance grow, brings resistance change promptly.

It will be understood by those skilled in the art that the above-described deformations are not meant to be merely perceptible (i.e., perceptible without the aid of external equipment), but in fact, are typically microscopic and small.

Fabric wire

"textile strands" are defined as threads used in textile fabrics, either woven or nonwoven. The textile threads may be natural threads, such as cotton threads, hemp threads, or polyester threads.

The fabric wire in the application can be single or several and not form interweaving, and also can form interweaving. May be single stranded or may be multi-stranded.

In a preferred embodiment, the fabric strands have a modulus of elasticity that is substantially greater than the modulus of elasticity of the conductive coating. Therefore, when the hydrogel sheet swells, the fabric wire can generate deformation obviously on the conductive coating layer, and then the deformation in the length direction is generated in preference to the conductive coating layer, and finally the deformation of the conductive coating layer in the length direction is driven.

The elastic modulus of the textile yarn is preferably 0.01 to 0.1MPa, for example, 0.01MPa, 0.02MPa, 0.05MPa, 0.08MPa, 0.09MPa, 0.1 MPa. If the elastic modulus is too small, the fabric wires are difficult to deform in response to swelling of the hydrogel sheet; if the elastic modulus is too large, the conductive coating layer may be driven to be easily subjected to structural damage such as fracture, so that continuous change of the resistance is not brought (that is, the resistance may stay at a resistance value corresponding to the structural damage, and then hardly changes).

The textile wire material of the present invention may be a polyester wire for a bandage, but may be other high-elasticity wire.

The fabric wire of the present application may be located on the surface of the fabric wire, or may be located inside the water-absorbing swelling component, preferably inside the water-absorbing swelling component, so that the fabric wire can be stably "pulled" when the water-absorbing swelling component absorbs water to swell, thereby increasing the stress response rate of the conductive coating layer to the swelling volume change of the water-absorbing swelling component.

One example of the operation of the fabric wires inside the water-absorbing swelling assembly is to cast a hydrogel layer with a certain thickness on a substrate (such as teflon material), adhere the fabric wires to the hydrogel layer directly by using the viscosity of the hydrogel, and cast the hydrogel layer with a certain thickness, so that the fabric wires can be sealed inside the hydrogel.

Similarly, a certain groove can be arranged on the water absorption swelling component, and the fabric wire material which is soaked with the conductive liquid penetrates into the groove by using the viscosity of the fabric wire material before the conductive liquid is dried so as to be adhered to the wall of the groove.

Water-absorbing swelling assembly

The water-absorbing swelling member is made of a water-absorbing swelling material which has water-absorbing property and swells after absorbing water. As one implementation mode, the water-swelling material can be hydrogel or water-swelling elastomer.

The water-swellable component herein has a swelling ratio of 500 to 2000, for example, 500, 550, 600, 700, 900, 1100, 1200, 1500, 1800, 1900, 2000, etc., in pure water, and a swelling ratio of 20 to 200, for example, 20, 30, 50, 80, 100, 110, 120, 150, 160, 180, 190, 200, etc., in 1mM sodium chloride salt water. If the swelling ratio is too large, structural damage such as fracture of the conductive coating layer can be caused; if the swelling ratio is too small, on the one hand, deformation of the textile strands is difficult to form, and on the other hand, insufficient absorption of perspiration may result.

The water-swellable elastomer can be obtained by the patent literature, such as "swelling kinetics of super absorbent resin [ J ]. Zhou Jian Qin, Zhu fai-Ku functional polymer journal 2007 (01)", "water-swellable elastomer (Zhang Shuxiang, Cheng Yong, Jia Shu. water-swellable elastomer swelling behavior in different media,. Polymer journal 1998, (4): 438-.

The water-swellable agent of the present application is preferably a hydrogel in view of biocompatibility. Hydrogels are a class of very hydrophilic three-dimensional network-structured gels that swell rapidly in water and in this swollen state can hold a large volume of water without dissolving. Due to the presence of the crosslinked network, the hydrogel can swell and retain a large amount of water, the amount of water absorbed being closely related to the degree of crosslinking. The higher the degree of crosslinking, the lower the water absorption.

As the material having the specific swelling ratio, the hydrogel sheet may be a PVA-PAA composite hydrogel. The PVA-PAA composite hydrogel is a hydrogel in which PVA (polyvinyl alcohol) and PAA (polyacrylic acid or a salt thereof) are both in a gel phase.

The preparation of PVA-PAA composite hydrogel can be obtained by adopting a known thermal crosslinking method to increase the mechanical property and the water absorption capacity of the PVA-PAA composite hydrogel. One preparation method of thermal crosslinking can be exemplified. For example, the polyvinyl alcohol is obtained by crosslinking 50-60 wt% of polyvinyl alcohol and 40-50 wt% of sodium polyacrylate at 40 ℃. The polyvinyl alcohol and the sodium polyacrylate can be in the form of aqueous solution. In addition to the manner of obtaining thermal crosslinking, a freeze-thaw method may be used, as disclosed in the literature "synthesis of polyvinyl alcohol (PVA)/polyacrylic acid (PAA) composite hydrogels".

The shape of the water-absorbent swelling member may be a sheet shape (e.g., a circle), or any other shape. For the round sheet-shaped water-absorbing swelling component, the thickness is 40-300 μm in reference, and the diameter is 1-5 cm. Of course, the size has no particular influence on the effect of the present application.

Conductive coating layer

The conductive coating layer can be obtained by dip-coating in a conductive liquid followed by drying and curing. As the conductive coating's of this application dip-coating mode, thereby in order to obtain comparatively even coating and ensure better implementation effect, can pass (for example can utilize the needle and line guide to pass) the mould that scrapes that thickness is 5 ~ 50mm thick before the conducting solution is not dry with the fabric wire rod that has steeped the conducting solution to get rid of and dip in and attach at the unnecessary conducting solution in surface, avoid the inhomogeneous coating thickness that causes of piling up of this unnecessary conducting solution. Here, the scratch mould can be PDMS, PET, PU or other materials, and does not add the restriction in this application.

As the conductive liquid, the square resistance value is less than 50 omega/square, and the specific square resistance value can obtain better corresponding rate of resistance.

In order to obtain good adhesion and ensure the stable resistance of the conductive coating layer, the viscosity of the conductive liquid is 30-300P, such as 30P, 32P, 35P, 40P, 60P, 80P, 120P, 140P, 160P, 200P, 250P, 280P or 300P.

The rate of change of resistance of the conductive liquid when heated at 85 ℃ for 1000 hours is preferably 1 to 10%, for example, 1%, 1.5%, 2%, 3%, 5%, 8%, 10%, etc. The heat resistance is suitable, and the stability of the temperature environment can be ensured.

The conductive liquid is heated at a temperature of 40 ℃ and a relative humidity of 95% for 1000 hours, and the resistance change rate is preferably 1 to 10%, for example, 1%, 1.5%, 2%, 3%, 5%, 8%, 10%, etc. The heat resistance is suitable, and the stability of a humidity environment can be ensured.

As the conductive liquid of the present application, one or at least two specific examples of conductive silver paste, conductive copper ink, PTC conductive ink, and conductive oil can be cited.

The drying and curing temperature can be selected according to the nature of the actual conductive liquid, for example, the curing temperature can be, for example, 60 to 120 ℃, and the curing time can be, for example, 30 to 60min at the curing temperature.

Protective layer

The protective layer is used for protecting the water absorption swelling component from being polluted and a transmission circuit connected with the strain sensing fabric. The protective layer can be disposed on a surface of the water-absorbing swelling component. The material of the protective layer can be PET or other materials.

Wicking layer

The foregoing water-absorbing swelling member itself has sufficient sweat-absorbing capacity, and a wicking layer may be provided in order to further achieve collection and conduction of sweat to the swelling member. The wicking layer may be of the same material as the fabric strands.

Adhesive layer

The adhesive layer is used for adhering the water absorption swelling component to the skin to be tested. The adhesive layer may use the components of conventional bio-conductive adhesives, such as PVA, etc.

Sealing ring

The sealing ring has the function of defining a sweat collecting area together with the wicking layer, and preventing sweat from leaking from the sweat collecting area so as to influence the detection accuracy of the sweat amount.

The sealing ring rubber, hydrogel, silica gel, etc. are made of a material with good flexibility, preferably a biocompatible material.

According to one aspect of the present application, a sweat amount detection method is implemented using the sweat detection sensing device as described above.

The following can briefly describe the operation process of sweat amount detection with respect to the above sweat detection sensing device. The sweat sensing device is first wired to a resistance measuring device (e.g., a digital source meter Keithley 2400).

First, the rate of change Δ R/R with respect to resistance is plotted₀＝(△R/R₀＝(R-R₀)/R₀Wherein R represents a real-time resistance measurement of the strain sensing fabric, R₀Representing the initial resistance value of the strain sensing fabric) is linear with sweat volume. Specifically, a NaCl solution with a known concentration (e.g., 1mM) is injected into the sweat detection sensing device at a certain rate (e.g., 9 μ L/min), a series of resistance values displayed by the resistance measuring device are recorded, and then a linear relationship between the resistance change rate and the injected volume of the NaCl solution is obtained by linear fitting with the resistance change rate as a dependent variable and the injected volume of the NaCl solution as an independent variable.

And installing the sweat detection sensing device on the skin to be detected. And (3) reading the resistance change rate brought by sweat, and inverting the sweat amount (volume) according to the linear relation.

The sweat detects sensing device of this application absorbs the sweat and swells the emergence volume through the swelling subassembly that absorbs water, and the fabric wire rod produces the resistance change because of deformation brings under this swelling to turn into the volume of sweating volume into the resistance change rate that can observe reading, have like this better ability and detect out the sweat volume comparatively conveniently, and it is lower to detect out the limit.

Drawings

Fig. 1 is an SEM image of a fabric wire having a conductive coating layer according to an embodiment of the present application.

Fig. 2 is a strain-resistance curve of a fabric wire having a conductive coating layer according to an example of the present application.

Fig. 3 is a schematic view of a sweat detection sensing device attached to skin according to an embodiment of the present application.

Fig. 4 is a diagram of a sweat detection sensing device according to an embodiment of the present application before and after swelling with water.

Fig. 5 is a resistance response curve after water absorption of a fabric wire with a conductive coating layer provided in an embodiment of the present application.

Fig. 6 is a resistance response curve of a fabric wire with a conductive coating layer after water absorption according to an embodiment of the present application.

Fig. 7 is a standard curve of a strain sensor-based wearable sweat sensing hydrogel patch for sweat detection provided by embodiments of the present application.

In the figure: 20-fabric threads; 30-a water-swellable component; 40-a protective layer; 50-a sealing ring; 60-an adhesive layer; 70-wicking layer.

Detailed Description

The following are specific examples of the present application and further describe the technical solutions of the present application, but the present application is not limited to these examples.

Material

Unless otherwise specified, the following materials are all commercially available.

Example 1

The sweat sensing device of this example does not include protective layer 40, wicking layer 70, adhesive layer 60, and sealing ring 50.

Preparation of a fabric wire 20 having a conductive coating layer. Firstly, a single PBT wire is obtained from a commercially available PBT bandage, and then the PBT wire is immersed in conductive carbon ink to form a conductive coating; secondly, the thread passes through the PDMS film with the thickness of 5mm through the needle so as to enable the coating to be thinner and more uniform; ③ curing for 30 minutes in an oven at 80 ℃.

Assembly of the sweat detection sensing device. 10g of sodium polyacrylate was added to 400mL of water and stirred at 60 ℃ for 1 hour. Then dried overnight in an oven at 60 ℃ to form a gel-like mass. ② adding 10 percent of polyvinyl alcohol. And thirdly, coating the mixture on a Teflon model with a built-in fabric wire 20 with a conductive coating layer after fully mixing, and drying the mixture at 40 ℃ overnight to obtain the sheet sweat detection sensing device with the thickness of 160 mu m.

Example 2

Unlike example 1, the sheet sweat sensing device of this example has a thickness of 120 μm.

Example 3

Unlike example 1, the sheet sweat sensing device of this example has a thickness of 140 μm.

Example 4

Unlike example 1, the sheet form sweat sensing device of this example has a thickness of 180 μm.

Example 5

Unlike example 1, the thickness of the sheet sweat sensing device of this example was 200 μm.

Example 6

The sweat detection sensor can be directly worn on a human body without auxiliary accessories.

Unlike the previous embodiment, a protective layer 40, a wicking layer 70, an adhesive layer 60, and a sealing ring 50 are additionally provided.

Referring to fig. 3, the adhesive layer 60 is positioned closest to the skin and is used to adhere to the skin. The protective layer 40 is located on the outer surface of the water-absorbing swelling member 30. The sealing ring 50 is located on the skin-adjacent portion of the adhesive layer 60 and encloses a sweat collection area with the protective layer 40. A wicking layer 70 is located within the sweat collection region and is in direct contact with the skin.

Example 7

Unlike example 1, the textile wires 20 of the sweat detecting and sensing device of this example are all attached to the outer surface of the water-absorbent swelling member 30.

Example 8

Different from the embodiment 1, the sweat detecting and sensing device of the embodiment has the textile wire 20 partially embedded inside the water-absorbing and swelling component 30 and partially attached to the surface of the water-absorbing and swelling component 30.

Application example

The method for detecting the sweat amount by using the sweat detection sensor in any one of the above embodiments is as follows:

the sweat detection sensor obtained in example 1 was connected to a digital source meter Keithley 2400, the resistance measurement mode was selected, and a strain sensor-based wearable sweat detection hydrogel patch was injected with 1mM NaCl solution at a rate of 9 μ L/min, the resistance change was monitored, and the linear relationship between the rate of change in resistance and the volume of perspiration was plotted. And installing the sweat detection sensing device on the skin to be detected. And (3) reading the resistance change rate brought by sweat, and inverting the sweat amount (volume) according to the linear relation.

SEM characterization

The morphology of the fabric wire 20 with the conductive coating layer according to any of the above embodiments is characterized in a known manner.

Referring to fig. 1, it can be seen that the distribution of the conductive coating layer over the surface of the fabric wire 20 is substantially uniform.

Strain-resistance change test

The strain resistance change of the fabric wire 20 having the conductive coating layer according to any of the above embodiments was tested.

Please refer to fig. 2. As can be seen from the graph, the strain and the rate of change of resistance (Δ R/R) of the fabric wire 20₀＝(△R/R₀＝(R-R₀)/R₀Wherein R represents a real-time resistance measurement of the strain sensing fabric, R₀Representing the initial resistance value of the strain sensing fabric) generally exhibits a linear relationship.

Swelling test at different times after sweat absorption

After 5mL of 1mM NaCl (simulated sweat) solution is added to the sweat detection sensor obtained in example 1 once, the swelling of the patch with water absorption is observed, and please refer to fig. 4, which shows that the sweat detection sensor swells sweat obviously.

Resistance response test in resistance at different times after sweat absorption

The sweat detecting sensors obtained in examples 1, 7 and 8 were connected to a digital source meter Keithley 2400, and after selecting the resistance measuring mode, 5mL of 1mM NaCl solution was added at a time, and the change in resistance was monitored and recorded, as shown in fig. 5 and 6.

As can be seen from this fig. 5: the hydrogel with different thicknesses absorbs water to swell, the geometric shapes are expanded to different degrees, and the resistance response of the strain sensing fabric is different. The performance of the sensor with a thickness of 160 μm is optimal.

As can be seen in fig. 6, the resistance response is most sensitive in example 1, followed by example 7, and least sensitive in example 8, located entirely inside the water-swellable component 30.

Standard curve of sweat amount and resistance change rate

For the resistance change obtained in the above application example, a curve is obtained by linear fitting with the resistance change as an ordinate (dependent variable) and the perspiration volume as an ordinate (ordinate), see fig. 7.

As can be seen from the graph, there is a clear linear relationship between the measured change in resistance signal and the volume of perspiration.

Sweat detection concentration

The sweat detection sensing device obtained by the method has the advantages that the volume of detected sweat is 12 mu L-1.2 mL, and the detection limit is 10 mu L.

The specific embodiments described herein are merely illustrative of the spirit of the application. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the present application as defined by the appended claims.

Claims

1. A sweat detection sensing device, comprising:

a water-absorbent swelling member;

and a fabric wire rod arranged on the water absorption swelling component, wherein the surface of the fabric wire rod is provided with a conductive coating layer, and the fabric wire rod can deform in the length direction of the fabric wire rod under the water absorption swelling of the water absorption swelling sheet, so that the conductive coating layer can follow the deformation to cause resistance change.

2. The sweat detection sensing device of claim 1, wherein the fabric wire has an elastic modulus of 0.01 to 0.1 MPa;

preferably, the textile wire is a polyester wire for bandages.

3. A sweat detection sensor device according to any one of claims 1 to 2, wherein the water-absorbing swelling member has a swelling ratio of 500 to 2000 in pure water and a swelling ratio of 20 to 200 under 1mM water of sodium chloride salt;

preferably, the water-absorbing swelling member is a hydrogel sheet;

preferably, the hydrogel sheet is a PVA-PAA composite hydrogel.

4. A sweat detection sensing device according to any one of claims 1 to 3, wherein the conductive liquid used to form the conductive coating has a square resistance value <50 Ω/square;

preferably, the viscosity of the conductive liquid is 30-300P;

preferably, the resistance change rate of the conductive liquid heated for 1000 hours at the temperature of 85 ℃ is 1-10%;

preferably, the resistance change rate of the conductive liquid heated for 1000 hours at the temperature of 40 ℃ and the relative humidity of 95% is 1-10%;

preferably, the conductive liquid is one or at least two of conductive silver paste, conductive copper ink, PTC conductive ink and conductive oil.

5. The sweat detection sensing device of any one of claims 1 to 4, wherein the textile wires are disposed inside the water-absorbing swelling member.

6. The sweat sensing device of any one of claims 1 to 5, further comprising a protective layer disposed on a surface of the swelling member.

7. The sweat sensing device of any one of claims 1 to 6, further comprising a wicking layer disposed on a surface of the water-absorbing swelling component remote from the protective layer.

8. The sweat sensing device of any one of claims 1 to 7, further comprising an adhesive layer for adhering the water-absorbing swelling member to the skin to be tested.

9. The sweat sensing device of any one of claims 1 to 8, further comprising a sealing ring disposed on a surface of the adhesive layer.

10. A sweat detection method implemented using the sweat detection sensor device according to any one of claims 1 to 9.