A hydrogel-based wearable color-changing sensor for monitoring skin physiological signals

Abstract

The present invention discloses a hydrogel-based wearable color-changing sensor for monitoring skin physiological signals. The sensor comprises a hydrogel substrate and multiple filling slots disposed within the hydrogel substrate. The filling slots contain color-changing dye aggregates that respond to skin physiological signals. The sensor has a simple structure and is easy to manufacture, enabling rapid and simultaneous monitoring of multiple physiological signals.

Description

Technical Field

[0001] The present invention belongs to the field of wearable devices, and in particular relates to a color-changing sensor for monitoring skin physiological signals. Background Art

[0002] Wearable health monitoring devices can analyze and assess skin physiological signals in real time, improving health and preventing disease. However, most flexible electronic devices used in wearable health monitoring devices convert skin physiological signals into electrical signals, requiring a large number of external instruments and equipment to collect and analyze the converted electrical signals, making the monitoring process cumbersome and complex. Wearable color-changing sensors convert physiological signals directly into optical signals visible to the naked eye, offering greater real-time monitoring capabilities and becoming a crucial component of health monitoring equipment.

[0003] Wearable color-changing sensors developed at home and abroad, on the one hand, achieve continuous monitoring of physiological signals by introducing reversible color-changing materials, such as the wearable UV exposure sensor disclosed in Chinese patent CN109425428A and the pH-sensitive color-changing fabric disclosed in CN106521987A; on the other hand, they achieve long-term and stable monitoring of physiological signals by introducing adhesive base materials, such as the adhesive photonic crystal hydrogel sensor disclosed in Chinese patent CN114149544A and the rapid hemostatic hydrogel disclosed in CN109331216A. However, the current technical bottleneck is that when such color-changing sensors monitor multiple signals simultaneously, they generally use color-changing materials that can respond to different physiological signals, which leads to information interference and the inability to respond continuously. To this end, the temperature-detecting body temperature patch disclosed in Chinese patent CN214906799U adopts a composite layer structure formed by a thermal conductive layer, a temperature-changing layer and a visual layer, and the temperature-changing layer contains multiple groups of temperature-changing zones. However, the patented composite layer structure design prevents the skin from exchanging and transferring substances with the color-changing material, is not suitable for sensors that simultaneously monitor UV, pH, and temperature, and has a slow response speed.

[0004] In addition, although the above-mentioned adhesive base material improves the adhesion when in contact with the skin, this type of base material often has poor plasticity, which is not conducive to arranging different color-changing materials thereon in different zones. Summary of the Invention

[0005] The purpose of the present invention is to provide a hydrogel-based wearable color-changing sensor that can monitor skin physiological signals. The sensor has a simple structure, is easy to process, and can achieve rapid monitoring of multiple physiological signals simultaneously.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The color-changing sensor comprises a hydrogel substrate and a plurality of filling grooves arranged on the hydrogel substrate, wherein color-changing dye aggregates for responding to skin physiological signals are arranged in the filling grooves.

[0008] Preferably, the color-changing dye aggregate is formed by wetting or dispersing the color-changing dye with an organic solvent and then drying it (the main purpose of drying is to remove the organic solvent).

[0009] Preferably, the organic solvent is selected from one or more of acetone, ethyl acetate, phthalate, etc., and can be replaced by nail polish with the same or similar solvent composition.

[0010] Preferably, different filling grooves on the hydrogel substrate contain color-changing dyes for responding to a variety of different skin physiological signals such as pH, ultraviolet (UV), temperature, etc.

[0011] Preferably, different filling grooves on the hydrogel substrate contain color-changing dyes for responding to different temperature ranges.

[0012] Preferably, the hydrogel substrate is made of polyacrylic acid hydrogel.

[0013] Preferably, the hydrogel substrate is formed by cross-linking acrylic acid, acrylamide and tannic acid in a mold.

[0014] Preferably, the initial concentration of acrylic acid in the cross-linking system is 0.1-0.5 g / mL, the initial concentration of acrylamide in the cross-linking system is 0.01-0.05 g / mL, and the initial concentration of tannic acid in the cross-linking system is 0.05-0.09 g / mL.

[0015] Preferably, the initiator used for the cross-linking is selected from one or more of potassium persulfate (KPS), ammonium persulfate (APS), etc., and the initial concentration of the initiator in the cross-linking system is 10-20 mg / mL.

[0016] Preferably, the crosslinking agent used in the crosslinking is selected from one or more of N,N'-Methylene Bis Acrylamide (MBA) and poly(ethylene glycol) diacrylate-700 (PEGDA-700), and the initial concentration of the crosslinking agent in the crosslinking system is 5-7 mg / mL.

[0017] Preferably, the cross-linking reaction conditions include: placing at 20-27° C. under an inert atmosphere for 8-14 hours.

[0018] Preferably, the color-changing sensor further comprises a water-blocking protective film, which is provided on the surface of the hydrogel substrate that is not in contact with the skin.

[0019] Preferably, the filling groove is located on the surface that does not contact the skin, and the water-blocking protective film covers the surface area of ​​the hydrogel substrate outside the filling groove.

[0020] Preferably, the water-blocking protective film is a plastic film.

[0021] Preferably, the distance between the color-changing dye aggregate and the skin is 0.5-1.5 mm.

[0022] The beneficial effects of the present invention are embodied in:

[0023] The wearable color-changing sensor of the present invention uses hydrogel as the base material and, by providing multiple filling grooves, enables the color-changing material to quickly respond to the physiological signals of the skin-adhesive area of ​​the base material, thereby achieving the effect of continuous and interference-free real-time and long-term stable monitoring of multiple skin physiological signals.

[0024] Furthermore, the hydrogel substrate in the present invention is formed by cross-linking acrylic acid, acrylamide and tannic acid, so that the substrate portion of the wearable color-changing sensor can be integrally formed in a mold and easily separated from the mold, which is convenient and quick, and promotes the widespread application of hydrogel-based color-changing sensors in the field of health monitoring.

[0025] Furthermore, the hydrogel substrate of the present invention can improve adhesion by introducing and adjusting the concentration of tannic acid based on the polyacrylic acid hydrogel cross-linking system.

[0026] Furthermore, by introducing a water-blocking protective film, the present invention can reduce the water loss of the hydrogel substrate, allowing the wearable color-changing sensor to be peeled and adhered to the skin multiple times, thereby improving the performance and life of the hydrogel-based color-changing sensor in the field of health monitoring.

[0027] Furthermore, the present invention utilizes the depth of the filling groove to control the thickness of the base hydrogel material between the color-changing dye solid body and the skin, which not only enables the wearable color-changing sensor to independently and continuously monitor multiple physiological signals, but also ensures that the user can read different physiological signals through the color change results at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the mold structure: Figure 1 In the middle, 1-upper sealing plate, 2-lower sealing plate, 3-backing plate, 4-forming plate, 5-mounting hole.

[0029] Figure 2Schematic diagram of the wearable color-changing sensor before (A) and after (B) filling with color-changing dye; Figure 2 Middle, 6-color-changing dye, 7-groove, 8-hydrogel substrate.

[0030] Figure 3 Schematic diagram of the stretching, compression and adhesion of hydrogel materials.

[0031] Figure 4 Schematic diagram of the working process of a wearable color-changing sensor prepared using a mold to monitor multiple skin physiological signals.

[0032] Figure 5 Schematic diagram of the working process of a wearable color-changing sensor that can monitor skin temperature signals prepared using a mold.

[0033] Figure 6 Schematic diagram of the color change range of three dyes that change color in response to pH, temperature and ultraviolet light. DETAILED DESCRIPTION

[0034] The present invention will be further described in detail below with reference to the accompanying drawings and examples, which are only used to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0035] (1) Preparation of wearable color-changing sensor

[0036] The first step is Figure 1 As shown, the structural parts of the three-layer mold are processed on a polymethyl methacrylate (PMMA) plate using a laser cutting machine.

[0037] The first layer of the mold includes an upper sealing plate 1 (×1 piece) with mounting holes 5 at four corners cut out according to the following size parameters: length 30mm, width 20mm, thickness 2mm; mounting hole diameter 2mm (hole center distance 3mm).

[0038] The second layer of the mold includes two backing plates 3 with mounting holes 5 on both sides, cut to the following dimensions: 30 mm long, 4 mm wide, and 2 mm thick; the mounting holes have a diameter of 2 mm (the center of the holes is 3 mm from the edges). The second layer also includes three shaping plates 4 cut to the following dimensions: 4-10 mm (e.g., 5 mm) long, 4-10 mm (e.g., 5 mm) wide, and 1 mm thick. The shaping plates 4 can be either square or rectangular, and can also have rounded corners.

[0039] The third layer of the mold includes a lower sealing plate 2 (×1 piece) with mounting holes 5 at four corners cut out according to the following size parameters: length 30mm, width 20mm, thickness 2mm; mounting hole diameter 2mm (hole center distance 3mm).

[0040] Step 2: Assembling the three-layer mold

[0041] The three shaping plates 4 are glued and fixed side by side at equal intervals on the side surface of the upper sealing plate 1 or the lower sealing plate 2, leaving a certain distance from the mounting holes 5 on the edge of the upper sealing plate 1 or the lower sealing plate 2. Then, the mounting holes 5 of the two pads 3 are aligned with the mounting holes 5 on the edge of the upper sealing plate 1 or the lower sealing plate 2, respectively, and the long sides of the pads 3 are flush with the long sides of the upper sealing plate 1 or the lower sealing plate 2. Then, the upper sealing plate 1 and the lower sealing plate 2 are stacked under the support of the two pads 3, and the mounting holes 5 of the upper sealing plate 1 and the lower sealing plate 2 are aligned one by one. The upper sealing plate 1, the pads 3 and the lower sealing plate 2 are fastened at the aligned mounting holes 5 using screws and nuts. Since the above structural parts are made of polymethyl methacrylate (PMMA) plate, the appearance of the corresponding assembled mold is colorless and transparent.

[0042] In the third step, the assembled three-layer mold is placed in a mixed aqueous solution (10 mL) formed by monomers (acrylic acid and acrylamide), initiator, cross-linking agent and tannic acid as solutes, and nitrogen is passed through the solution to remove oxygen. After passing nitrogen for 10 minutes, the solution is placed at room temperature for 12 hours without UV irradiation to form a self-adhesive hydrogel (cross-linked by acrylic acid, acrylamide and tannic acid in the mixed aqueous solution entering the above-mentioned internal space, see Table 1) in the three-layer mold (specifically, in the semi-enclosed internal space of the mold between the upper and lower sealing plates 1, 2 and the pad 3). After disassembling the three-layer mold, the following can be obtained: Figure 2 A shows a hydrogel substrate 8 (the three shaping plates 4 located in the internal space serve as inner molds for forming the three grooves 7 on the hydrogel substrate 8).

[0043] Table 1. Cross-linking parameters of self-adhesive hydrogels

[0044]

[0045] Table 2. Performance test data of self-adhesive hydrogel

[0046] Adhesion Tensile force Compression force plasticity Allergenicity Example 1 14.8kPa 305kPa 398kPa good No redness, swelling, or itching Example 2 14.5kPa 297kPa 400kPa good No redness, swelling, or itching Example 3 13.7kPa 301kPa 382kPa good No redness, swelling, or itching Control 1 29.5kPa 155kPa 312kPa good No redness, swelling, or itching Control 2 5.4kPa 312kPa 402kPa good No redness, swelling, or itching

[0047] As shown in Table 2, the self-adhesive hydrogels prepared in Examples 1, 2, and 3 have strong adhesion, but the hydrogel prepared in Control 1 ( Figure 3 ) due to its excessively strong adhesion, which makes it difficult to separate from the mold after being formed through cross-linking.

[0048] The fourth step is to embed different stimulus-responsive color-changing dyes 6 into different grooves 7 on the hydrogel substrate 8 to prepare a wearable color-changing sensor ( Figure 2 B).

[0049] To prevent the evaporation of water contained in the hydrogel substrate 8, a layer of polyvinyl chloride (PVC) film can be applied to the side of the hydrogel substrate 8 where the color-changing dye 6 is embedded, but this film does not cover the color-changing dye 6. When the wearable color-changing sensor is used, the other side of the hydrogel substrate 8 is applied to the skin.

[0050] (2) Using wearable color-changing sensors to monitor pH, temperature, and UV physiological signals

[0051] A hydrogel substrate 8 was prepared according to Example 1. Three dyes that change color in response to pH, temperature, and ultraviolet light, respectively, were embedded into three grooves 7 on the hydrogel substrate 8. The dyes that change color in response to ultraviolet light (photochromic dye) and temperature (thermochromic dye) are commercially available, and the dye that changes color in response to pH is bromothymol blue. The dye embedding process is as follows: nail polish is used to prepare slurries of the three dyes mentioned above. Each slurry of the dye is added to the corresponding groove 7, filling the groove. The slurries are then naturally evaporated at room temperature to form a dye block with a certain hardness that is solidified in the groove 7.

[0052] The experimental results show that the obtained sensor can be attached to any part of the skin and can monitor pH (skin external environment), temperature (skin surface) and ultraviolet light (skin external environment) ( Figure 4 、 Figure 6 ), monitoring conditions: ambient temperature is 15-35℃, humidity is 40%-70%.

[0053] (3) Using wearable color-changing sensors to monitor skin temperature signals

[0054] A hydrogel substrate 8 was prepared according to Example 1. Dyes (thermochromic dye) that change color in response to different temperatures were embedded into three grooves 7 on the hydrogel substrate 8 .

[0055] The obtained sensor is attached to the surface of human skin. Users can directly judge the temperature of the corresponding area on the skin surface by the color of the dye in the three partitions (i.e. the areas corresponding to the three grooves 7), so that users can understand their health information anytime and anywhere, and the accuracy is consistent with that of a thermometer ( Figure 5 ), before the test, the sensor was preheated with moderate hot water to fit the skin. Figure 6 It can be seen that the temperature reflected by the dyes in the three partitions of the sensor from top to bottom is 33℃ ( Figure 5 The laser position of the thermometer is the position of the top partition), 35℃ and 38℃.

Claims

1. A hydrogel-based wearable color-changing sensor, characterized by: The color-changing sensor comprises a hydrogel substrate (8) and a plurality of filling grooves arranged on the hydrogel substrate (8), wherein color-changing dye aggregates for responding to skin physiological signals are arranged in the filling grooves; The hydrogel substrate (8) is formed by cross-linking acrylic acid, acrylamide and tannic acid in a mold; The color-changing sensor further comprises a water-blocking protective film, which covers the surface area of ​​the hydrogel substrate (8) outside the filling groove.

2. The hydrogel-based wearable color-changing sensor according to claim 1, characterized in that: The color-changing dye aggregate is formed by wetting or dispersing the color-changing dye with an organic solvent and then drying it.

3. The hydrogel-based wearable color-changing sensor according to claim 1, characterized in that: Different filling grooves on the hydrogel substrate (8) contain color-changing dyes for responding to a variety of different signals such as pH, ultraviolet light, and temperature.

4. The hydrogel-based wearable color-changing sensor according to claim 1, characterized in that: Different filling grooves on the hydrogel substrate (8) contain color-changing dyes for responding to different temperature ranges.

5. The hydrogel-based wearable color-changing sensor according to claim 1, characterized in that: The concentration of acrylic acid in the cross-linking system is 0.1-0.5 g / mL, the concentration of acrylamide in the cross-linking system is 0.01-0.05 g / mL, and the concentration of tannic acid in the cross-linking system is 0.05-0.09 g / mL.

6. The hydrogel-based wearable color-changing sensor according to claim 1, characterized in that: The initiator used for the crosslinking is selected from one or more of potassium peroxydisulfate and ammonium peroxydisulfate, and the concentration of the initiator in the crosslinking system is 10-20 mg / mL; the crosslinking agent used for the crosslinking is selected from one or more of MBA and PEGDA-700, and the concentration of the crosslinking agent in the crosslinking system is 5-7 mg / mL.

7. The hydrogel-based wearable color-changing sensor according to claim 1, characterized in that: The cross-linking reaction conditions include: placing at 20-27° C. under an inert atmosphere for 8-14 hours.

8. The hydrogel-based wearable color-changing sensor according to claim 1, characterized in that: The distance between the color-changing dye solid body and the skin is 0.5-1.5 mm.

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