Passive wearable sweat-based liquid temperature monitoring wristband based on thermoelectric gel and preparation method

Abstract

The application provides a passive wearable sweat body temperature monitoring bracelet based on a thermoelectric gel, and belongs to the technical field of thermoelectric gel sensors; solves the problem that current sensors need auxiliary power supply equipment and the preparation process is complex; raw materials including an oxidation-reduction pair, a conductive ion salt, a binary solvent, a certain amount of gelatin and polyvinylpyrrolidone are uniformly mixed through high-temperature stirring melting, and then the thermoelectric gel sensor can be rapidly and batch-prepared through low-temperature gelation; the gel cold end is integrated with water-absorbing sponge or medical gauze, and the diffusion current generated by the ion concentration gradient diffusion is utilized to realize the diffusion, collection and detection functions of sweat; the gel hot end is directly conformally attached to the human skin, and the thermoelectric effect of the oxidation-reduction pair under a certain temperature difference is utilized to realize the real-time monitoring function of the human body temperature; the sensor realizes the function of non-invasive passive monitoring of human sweat and body temperature, and can be applied to human health monitoring.

Description

Technical Field

[0001] This invention belongs to the field of electronic information technology, specifically relating to a thermoelectric gel based on redox pairs, and more particularly to a passive wearable sweat temperature monitoring bracelet based on thermoelectric gel and its preparation method. Background Technology

[0002] Thermoelectric technology, which generates electricity by utilizing the temperature difference between high and low temperature heat sources, has attracted widespread attention because it can convert heat into electrical energy without producing byproducts or consuming additional materials. In various applications, converting waste heat energy into electrical energy for signal detection is valuable. However, thermoelectric sensors made from traditional semiconductor materials often have low Seebeck coefficients, are rigid and inflexible, resulting in poor environmental adaptability and limited application range. In recent years, wearable sweat and temperature sensors have made significant progress, but most require auxiliary power and have complex fabrication processes, hindering large-scale commercial applications. Therefore, the development of simple and economical passive wearable health monitoring technology is urgently needed. Summary of the Invention

[0003] This invention studies and explores a flexible, stretchable thermoelectric gel based on redox pairs, with the aim of providing a passive wearable sweat temperature monitoring bracelet based on thermoelectric gel and its preparation method, so as to realize non-invasive passive monitoring of human sweat and body temperature.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a passive wearable sweat temperature monitoring bracelet based on thermogel, comprising a sweat and body temperature monitoring sensor, a sweat-absorbing layer, and an encapsulation shell; the sweat and body temperature monitoring sensor is a thermogel sensor; the sweat-absorbing layer is a water-absorbing sponge or medical gauze; the encapsulation shell is made of polydimethylsiloxane and is in the shape of a bracelet to achieve passive wearable real-time monitoring; one side of the encapsulation shell is provided with an array of circular holes for sweat circulation and diffusion, and the other side of the encapsulation shell is provided with a rectangular hole for attaching to the human body for body temperature measurement.

[0005] The thermoelectric gel sensor measures 3cm × 1cm and has a thickness of 1mm.

[0006] A method for preparing a passive wearable sweat temperature monitoring wristband based on thermoelectric gel includes the following steps:

[0007] a) Prepare a mixture of redox pairs and conductive ion salts with a certain molar concentration, dissolve it in a mixed solvent of deionized water and glycerol, stir the solution thoroughly, add 1-2g of gelatin and 0.1-0.3g of polyvinylpyrrolidone to the solution, and stir at a constant temperature of 75℃ for 1-2 hours until a homogeneous mixed solution is obtained.

[0008] b) After the reaction is complete, the homogeneous solution is left to stand in an unstirred oil bath for a period of time to remove air bubbles. Then the solution is transferred to a PTFE mold and placed at 4°C for a period of time to gel, thus obtaining a thermoelectric gel sensor.

[0009] c) Integrate and encapsulate the thermoelectric gel sensor, absorbent sponge, or medical gauze obtained in step b using PDMS to obtain a passive wearable sweat and body temperature monitoring bracelet.

[0010] The redox pair is provided by the corresponding redox substance and can produce a thermal voltage effect. The redox pair is specifically FeCl3 / FeCl2, K3Fe(CN)6 / K4Fe(CN)6, I2 / KI or Na2SO4 / Na2SO3.

[0011] The deionized water is purified from the Millipore reverse osmosis system, the gelatin is of photographic purity with a strength of ~250gBloom, and the polyvinylpyrrolidone used has an average molecular weight of 58,000 and is of type K29-32.

[0012] The Seebeck coefficient of the thermoelectric gel sensor exceeds 1.0 mV / K.

[0013] Step c involves encapsulating the entire thermoelectric gel sensor and sweat-absorbing layer in PDMS using a single casting process. Specifically, at the sweat-absorbing layer, which is the cold end of the thermoelectric gel sensor, a 3×3 array of 1mm×1mm diameter circular holes is punched in the PDMS to allow for sweat circulation and diffusion. At the hot end of the thermoelectric gel sensor, a 1.5cm×1.0cm rectangular hole is cut in the PDMS using a blade, allowing the hot end of the thermoelectric gel sensor to be directly attached to the human skin for real-time body temperature monitoring.

[0014] The advantages of this invention compared to existing technologies are as follows: The thermoelectric gel sensor prepared by this invention only requires some inexpensive and simple raw materials: gelatin, polyvinylpyrrolidone, redox agents, glycerol, deionized water, etc. Specifically, after uniformly mixing the reaction solution at 75°C, the solution is poured into a PTFE mold and placed at 4°C for 1 hour to form a gel. The operation procedure is simple, requires few parameters to be adjusted during synthesis, and has low synthesis cost. The redox-based thermoelectric gel sensor obtained by this invention has excellent flexibility, stretchability, and good conductivity under extreme conditions. It also has strong water retention, temperature resistance, and fatigue fracture resistance.

[0015] Furthermore, this passive wearable sweat and body temperature monitoring bracelet exhibits excellent sensing performance. Specifically, when the human body sweats, the sweat diffuses through the absorbent layer to the cold-end interface of the hydrogel. The hydrogel, as a high-performance water-absorbing and water-retaining material with a stable three-dimensional network structure, can absorb a large amount of sweat in a short time. Sweat contains a large number of electrolytes, such as sodium, potassium, and calcium ions. Through diffusion of the ion concentration gradient, a corresponding diffusion current can be generated in the gel system. By plotting a standard concentration curve based on the current magnitude, the concentration and type of electrolytes in the sweat can be obtained. Simultaneously, due to the temperature difference (around 10°C) between the surrounding environment and the human body, the thermoelectric effect of the thermogel can be used to generate a thermal voltage output, enabling real-time monitoring of the human body temperature.

[0016] The biggest difference between this invention and existing sweat and body temperature monitoring devices is that it can simultaneously achieve passive sensing of sweat and body temperature without complicated preparation and operation processes, making it more convenient for real-time monitoring of human physiological conditions and having broad application prospects in the field of passive wearable health monitoring. Attached Figure Description

[0017] The present invention will be further described below with reference to the accompanying drawings:

[0018] Figure 1 This is a schematic diagram of the structure of a passive wearable sweat and body temperature monitoring wristband based on thermogel prepared by the method of the present invention.

[0019] Figure 2 a is a tensile stress-strain curve of the thermogel sensor prepared by the method of the present invention at different temperatures.

[0020] Figure 2 b is a graph showing the change in conductivity of the thermogel sensor prepared by the method of the present invention at different temperatures.

[0021] Figure 3 a represents the voltage and current changes of the thermoelectric gel sensor prepared by the method of this invention at different numbers of days.

[0022] Figure 3 b is a graph showing the change in water content of the thermogel sensor prepared by the method of the present invention over different days.

[0023] Figure 4 The temperature-current-voltage relationship curve of the thermoelectric gel sensor prepared by the method of the present invention.

[0024] Figure 5 Current response curves of the thermogel sensor prepared by the method of this invention to different concentrations and types of electrolytes. Detailed Implementation

[0025] like Figures 1 to 5As shown, this invention provides a passive wearable sweat and body temperature monitoring wristband based on thermogel. The wristband comprises three parts: a sweat and body temperature monitoring sensor, a sweat-absorbing layer, and a casing. The sweat and body temperature monitoring sensor is a thermogel sensor; the sweat-absorbing layer is an absorbent sponge or medical gauze; the casing is made of polydimethylsiloxane and is shaped like a wristband to achieve passive wearable real-time monitoring. The gel sensor has a size of 3cm × 1cm and a thickness of 1mm.

[0026] This invention also provides a method for preparing a passive wearable sweat and body temperature monitoring wristband based on thermogel, comprising the following steps:

[0027] a) Prepare a mixture of redox pairs and conductive ion salts with a certain molar concentration, dissolve it in a mixed solvent of deionized water and glycerol, stir the solution thoroughly for 30 minutes, add 1-2g of gelatin and 0.1-0.3g of polyvinylpyrrolidone to the solution, and stir at a constant temperature of 75℃ for 1-2 hours until a homogeneous mixed solution is obtained.

[0028] b) After the reaction is complete, the mixed solution is left to stand in an unstirred oil bath for 1 hour to remove air bubbles. Then the solution is transferred to a PTFE mold and placed at 4°C for 1 hour to gel, thus obtaining a thermoelectric gel sensor.

[0029] c) Integrate and encapsulate the thermoelectric gel sensor obtained in step b with an absorbent sponge or medical gauze using PDMS to obtain a suitable passive wearable sweat and body temperature monitoring wristband.

[0030] The redox pairs that produce the thermal voltaic effect are provided by the corresponding redox substances, such as FeCl3 / FeCl2, K3Fe(CN)6 / K4Fe(CN)6, I2 / KI, or Na2SO4 / Na2SO3, etc.

[0031] Deionized water was purified from a Millipore reverse osmosis system. Gelatin was of photographic purity with a strength of ~250gBloom. The polyvinylpyrrolidone used had an average molecular weight of 58,000 and was of type K29-32. All of these were purchased from Aladdin Reagents Ltd.

[0032] The Seebeck coefficient of the thermogel sensor exceeds 1.0 mV / K.

[0033] Thermogel sensors are flexible and stretchable, have long operating cycles (10 days), and a wide operating temperature range (-20°C to 60°C).

[0034] Thermogel sensors, due to the temperature-controlled adhesion of gelatin, can achieve good conformal adhesion to skin tissue and sweat-absorbing layers.

[0035] The materials used to prepare gel sensors are low in cost, abundant in source, and have good biocompatibility, making them perfectly suitable for human health monitoring.

[0036] Step c involves encapsulating the entire thermoelectric gel sensor and sweat-absorbing layer using PDMS in a single casting process. Specifically, at the sweat-absorbing layer (the cold end of the gel), a 3×3 array of 1mm×1mm diameter circular holes is punched into the PDMS to allow for sweat circulation and diffusion. At the hot end of the gel, a 1.5cm×1.0cm rectangular hole is cut into the PDMS using a blade, allowing the hot end of the gel sensor to be directly attached to the human body for real-time body temperature monitoring.

[0037] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments, such as... Figure 1 A schematic diagram of the overall structure of a passive wearable sweat and body temperature monitoring wristband is shown. Figure 2 The prepared thermogel exhibits excellent antifreeze and anti-drying properties. Figure 3 These are test graphs showing the long-term dehydration, electrical properties, and water content of the thermoelectric gel, indicating that the gel has the ability to work over a long period of time. Figure 4 It was demonstrated that the voltage and current output of the thermoelectric gel are linearly correlated with temperature, and can be used for real-time monitoring of human body temperature; Figure 5 This indicates that thermogels can be used to distinguish between different concentrations and types of electrolytes, enabling non-invasive detection of human sweat.

[0038] Example 1

[0039] The specific operating steps are as follows:

[0040] Step 1: Prepare a mixture of 0.08M iodine, 0.16M potassium iodide and 0.5M sodium chloride. Dissolve the mixture in a mixed solvent of deionized water (6g) and glycerol (4g). Stir the solution thoroughly for 30 minutes. Then add 1.6g gelatin and 0.1g polyvinylpyrrolidone to the solution and stir at 75℃ for 1-2 hours until a homogeneous mixed solution is obtained.

[0041] Step 2: After the reaction is complete, let the mixed solution stand in an unstirred oil bath for 1 hour to remove air bubbles, then transfer the solution to a PTFE mold and place it at 4°C for 1 hour to gel.

[0042] Step 3: Integrate and encapsulate the thermoelectric gel sensor obtained in Step 2 with an absorbent sponge or medical gauze using PDMS to obtain a suitable passive wearable sweat and body temperature monitoring bracelet.

[0043] Example 2

[0044] Step 1: Prepare a mixture of 0.1M ferric chloride, ferrous chloride and 0.5M potassium chloride. Dissolve the mixture in a mixed solvent of deionized water (6g) and glycerol (4g). Stir the solution thoroughly for 30 minutes. Then add 1.8g gelatin and 0.2g polyvinylpyrrolidone to the solution and stir at a constant temperature of 75℃ for 1-2 hours until a homogeneous mixed solution is obtained.

[0045] Step 2: After the reaction is complete, let the mixed solution stand in an unstirred oil bath for 1 hour to remove air bubbles, then transfer the solution to a PTFE mold and place it at 4°C for 1 hour to gel.

[0046] Step 3: Integrate and encapsulate the thermoelectric gel sensor obtained in Step 2 with an absorbent sponge or medical gauze using PDMS to obtain a suitable passive wearable sweat and body temperature monitoring bracelet.

[0047] Example 3

[0048] Step 1: Prepare a mixture of 0.1M potassium ferricyanide, potassium ferrocyanide and 1M lithium chloride. Dissolve the mixture in a mixed solvent of deionized water (6g) and glycerol (4g). Stir the solution thoroughly for 30 minutes. Then add 2.0g gelatin and 0.3g polyvinylpyrrolidone to the solution and stir at 75℃ for 1-2 hours until a homogeneous mixed solution is obtained.

[0049] Step 2: After the reaction is complete, let the mixed solution stand in an unstirred oil bath for 1 hour to remove air bubbles, then transfer the solution to a PTFE mold and place it at 4°C for 1 hour to gel.

[0050] Step 3: Integrate and encapsulate the thermoelectric gel sensor obtained in Step 2 with an absorbent sponge or medical gauze using PDMS to obtain a suitable passive wearable sweat and body temperature monitoring bracelet.

[0051] This invention utilizes redox pairs, conductive ionic salts, binary solvents, a certain amount of gelatin, and polyvinylpyrrolidone as raw materials. The raw materials are uniformly mixed through high-temperature stirring and melting, followed by low-temperature gelation to rapidly mass-produce thermoelectric gel sensors. Subsequently, the cold end of the gel is integrated with an absorbent sponge or medical gauze, utilizing the diffusion current generated by the diffusion of ion concentration gradients to simultaneously achieve the diffusion, collection, and detection of sweat. The hot end of the gel conformally adheres directly to human skin, utilizing the voltaic effect of the redox pairs under a certain temperature difference to achieve real-time monitoring of human body temperature. The sensor of this invention achieves non-invasive, passive monitoring of human sweat and body temperature, and has broad application prospects in the field of human health monitoring.

[0052] Regarding the specific structure of this invention, it should be noted that the connection relationships between the various component modules used in this invention are definite and achievable. Except as specifically described in the embodiments, their specific connection relationships can bring about corresponding technical effects and solve the technical problems proposed by this invention without relying on the execution of corresponding software programs. The models of the components, modules, and specific components appearing in this invention, the connection methods between them, and the conventional usage methods and expected technical effects brought about by the above technical features, unless specifically described, are all publicly disclosed content in patents, journal articles, technical manuals, technical dictionaries, and textbooks that can be obtained by those skilled in the art before the application date, or belong to conventional technology, common knowledge, and other existing technologies in this field. There is no need to elaborate, which makes the technical solution provided in this case clear, complete, and achievable, and can reproduce or obtain corresponding physical products based on this technical means.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A passive wearable sweat-based liquid temperature monitoring wristband based on thermoelectric gel, characterized by: The wearable sweat and body temperature monitoring bracelet comprises a sweat and body temperature monitoring sensor, a sweat absorbing layer and a packaging shell; the sweat and body temperature monitoring sensor is a thermoelectric gel sensor; the sweat absorbing layer is a water absorbing sponge or medical gauze; the packaging shell is made of polydimethylsiloxane and has a bracelet shape to realize passive wearable real-time monitoring; one side of the packaging shell is provided with an array of round holes for sweat circulation and diffusion; and the other side of the packaging shell is provided with a rectangular hole for attaching to the human body to measure the body temperature. When the human body sweats, the sweat is circulated and diffused to the water gel cold end interface of the thermoelectric gel sensor through the sweat absorbing layer; a large amount of electrolyte in the sweat is diffused through the ion concentration gradient to generate a corresponding diffusion current in the gel system; and the concentration and type of the electrolyte in the sweat can be obtained according to the standard concentration curve drawn according to the diffusion current size; meanwhile, the thermal voltage output is generated by the thermal electromotive force effect of the thermoelectric gel to realize real-time monitoring of the body temperature of the human body due to the temperature difference between the surrounding environment and the human body.

2. The passive wearable thermooptical gel-based sweat-based body temperature monitoring wristband of claim 1, wherein: The size of the thermoelectric gel sensor is 3cm×1cm, and the thickness is 1mm.

3. A method for preparing a passive wearable thermoelectric gel-based sweat-based body temperature monitoring wristband, characterized by: The method comprises the following steps: a) a mixture of a certain molar concentration of a redox couple and a conductive ion salt is dissolved in a mixed solvent of deionized water and glycerol; after the solution is stirred sufficiently, 1-2g of gelatin and 0.1-0.3g of polyvinylpyrrolidone are added to the solution and stirred at 75℃ for 1-2 hours until a uniform mixed solution is obtained; b) after the reaction is completed, the uniform mixed solution is placed in an oil bath without stirring for a period of time to remove bubbles, and then the solution is transferred to a PTFE mold and placed at 4℃ for a period of time to gel to obtain a thermoelectric gel sensor; c) the thermoelectric gel sensor obtained in step b), the water absorbing sponge or the medical gauze are integrated and packaged by PDMS to obtain a passive wearable sweat and body temperature monitoring bracelet; In step c, the entire thermoelectric gel sensor and the sweat absorbing layer are packaged by PDMS at one time, wherein a 3×3 array of 1mm×1mm diameter round holes is punched on the PDMS by a puncher at the place where the sweat absorbing layer is located, i.e. the cold end of the thermoelectric gel sensor, for the circulation and diffusion of sweat; and a 1.5cm×1.0cm rectangular hole is cut on the PDMS by a blade at the hot end of the thermoelectric gel sensor for directly attaching the hot end of the thermoelectric gel sensor to the human skin to realize real-time monitoring of the body temperature.

4. The method of claim 3, wherein the method further comprises: The redox couple is provided by corresponding redox substances and can generate thermal electromotive force effect; specifically, the redox couple is FeCl3 / FeCl2, K3Fe(CN)6 / K4Fe(CN)6, I2 / KI or Na2SO4 / Na2SO3.

5. The method of claim 3, wherein the method further comprises: mixing the thermoelectric gel with a liquid to form a mixture; and heating the mixture to a temperature of about 60 °C to about 70 °C. The deionized water is purified from a Millipore reverse osmosis system; the gelatin has a photographic grade, a strength of ~250g Bloom and the polyvinylpyrrolidone used has an average molecular weight of 58000 and a model of K29-32.

6. The method of claim 3, wherein the method further comprises: The Seebeck coefficient of the thermoelectric gel sensor is more than 1.0mV / K.

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