A flexible, breathable skin biosensor and method of manufacturing the same

Abstract

The application discloses a flexible and breathable skin biological sensor and a manufacturing method thereof, and the material of a flexible base layer of the flexible and breathable skin biological sensor is a functionalized porous polyimide flexible material. The flexible base layer is prepared by surface modification of a porous hydrophobic base and by a method of preparing a conductive electrode through temperature control screen printing. The interface stability and printing precision of the conductive pattern of the porous base are improved, the continuous skin detection of biological markers such as glucose can be realized, and the flexible and breathable skin biological sensor is especially suitable for batch manufacturing of a breathable skin electrochemical biological sensor.

Description

Technical Field

[0001] This invention relates to the field of wearable electronic devices and electrochemical sensing technology, and in particular to a flexible, breathable skin biosensor and its manufacturing method. Background Technology

[0002] Epidermal biosensors are flexible, non-invasive monitoring electronic devices with advantages such as softness, non-invasiveness, conformal adhesion, and wireless data transmission. Current epidermal biosensors require substrate materials with high flexibility, breathability, and skin compatibility. Electrospun polyimide, as a material with good mechanical properties, is widely used in such devices. However, its hydrophobicity and porous structure easily lead to problems such as poor adhesion of conductive patterns, uneven ink diffusion, and low pattern accuracy, seriously affecting the sensor's performance and lifespan. Traditional laser patterning, doping with conductive particles, or structural coatings can partially alleviate these issues, but they often have limitations such as complex equipment, high cost, or poor compatibility. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a flexible and breathable epidermal biosensor.

[0004] Another technical problem to be solved by the present invention is to provide a method for manufacturing the above-mentioned flexible breathable skin biosensor.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: A flexible, breathable epidermal biosensor, wherein the flexible substrate layer is made of functionalized porous polyimide flexible material.

[0006] The flexible base layer of the aforementioned flexible and breathable epidermal biosensor is a functionalized electrospun polyimide base layer. The functionalized porous polyimide flexible material used has undergone surface functionalization modification treatment, which allows it to conformally fit the skin and be used in wearable flexible epidermal electronic devices.

[0007] Preferably, in the above-mentioned flexible breathable epidermal biosensor, the thickness of the flexible substrate layer is 10 μm-50 μm.

[0008] Preferably, the aforementioned flexible breathable epidermal biosensor comprises, from top to bottom, a flexible substrate layer made of functionalized porous polyimide flexible material, an Ag wire layer, a sensor layer, and a protective layer.

[0009] The aforementioned method for manufacturing flexible, breathable skin biosensors involves processing electrochemical sensors on a porous flexible substrate using a surface functionalization unit and a temperature-controlled screen printing unit. The surface functionalization unit transforms hydrophobic interfaces into hydrophilic interfaces through plasma activation and silanization modification, thereby enhancing ink anchoring capabilities. The temperature-controlled screen printing unit integrates a constant-temperature platform and a screen gap fixing mechanism, optimizing ink rheological properties through temperature regulation and suppressing capillary diffusion.

[0010] Preferably, the manufacturing method of the above-mentioned flexible breathable epidermal biosensor is achieved by combining substrate surface functionalization modification with temperature-controlled screen printing, and the specific processing steps are as follows: Step S1: Cleaning the substrate: The electrospun polyimide porous material is ultrasonically cleaned with chemical reagents and dried with nitrogen to obtain a clean electrospun polyimide porous material. Step S2: Plasma activation: The electrospun polyimide porous material is treated with oxygen plasma to generate hydroxyl groups on its surface; Step S3: Preparation of silane-modified solution: Mix deionized water and ethanol, add acetic acid to adjust the pH of the solution to 4-6, add 3-aminopropyltriethoxysilane (APTES) at a concentration of 15-35 wt% to the solution, and stir for 2-6 minutes; Step S4: Silane modification spraying: The silane modification solution is sprayed onto the surface of the treated electrospun polyimide porous material using a pneumatic spraying method, and a thermal dehydration reaction is carried out at 50-100℃ to form an amino-containing silane network, thereby modifying the substrate surface and obtaining a functionalized porous polyimide flexible material. Step S5: Temperature-controlled screen printing: The functionalized porous polyimide flexible material is fixed on a heating platform of 25 ℃-65 ℃, and conductive silver paste, Ag / AgCl electrode ink and Prussian blue modified carbon ink are printed sequentially by screen printing to form a microstructure conductive electrode pattern; the printed electrodes are cured at 200-300 ℃ for 30-45 minutes to obtain a flexible breathable epidermal biosensor circuit; Step S6: A chitosan solution containing enzymes and platinum nanoparticles is dropped onto the surface of the working electrode, and a Nafion coating is applied to form a protective layer, thereby obtaining the flexible breathable epidermal biosensor.

[0011] Preferably, in the above-mentioned method for manufacturing the flexible breathable epidermal biosensor, oxygen plasma modifies the surface of the material to destroy its surface inert chemical layer and transform the hydrophilic hydroxyl interface.

[0012] Preferably, in the above-mentioned method for manufacturing the flexible breathable skin biosensor, the preferred concentration of the APTES solution is 20 wt%, and it is applied to the material surface using a pneumatic spraying method.

[0013] Preferably, in the above-mentioned method for manufacturing the flexible breathable skin biosensor, the temperature-controlled screen printing module regulates the rheological state of the ink printing by controlling the printing temperature.

[0014] The beneficial effects of this invention are: The aforementioned flexible, breathable epidermal biosensor is a type of flexible, breathable epidermal biosensor based on surface functionalization and temperature-controlled screen printing, enabling continuous epidermal detection of biomarkers such as glucose. A flexible substrate layer is prepared by modifying the surface of a porous hydrophobic substrate and fabricating conductive electrodes through temperature-controlled screen printing. This improves the interfacial stability and printing accuracy of the conductive pattern on the porous substrate, making it particularly suitable for the mass production of breathable epidermal electrochemical biosensors.

[0015] The sensor employs an innovative manufacturing method that combines material surface functionalization with a temperature-controlled printing strategy, effectively improving the interface stability and printing accuracy of conductive patterns while maintaining the breathability and flexibility of the substrate. The resulting flexible sensor possesses the following core advantages: its breathable design allows the substrate to conformally fit the skin, effectively promoting sweat evaporation and preventing the accumulation of biofluids; the electrode pattern exhibits high resolution and excellent bending stability, providing a reliable platform for wearable health management. This manufacturing method integrates surface functionalization and temperature-controlled screen printing units, solving the challenges of high-precision fabrication and mechanical stability of micron-level electrode patterns on porous hydrophobic substrates, while maintaining substrate breathability, providing a mass-producible manufacturing solution for long-term wearable epidermal electronic devices. Specifically: 1. Breakthrough in interface stability: Surface functionalization modification improves electrode peel strength and reduces resistance change during bending.

[0016] 2. Improved printing accuracy: Temperature-controlled screen printing improves the linewidth deviation and roughness of the sensor circuit and electrodes.

[0017] 3. Optimized Sensing Performance: The flexible, breathable epidermal biosensor boasts high moisture and air permeability, meeting skin breathability requirements and conformally adhering to the skin. This provides ample oxygen to the sensor, enhancing detection sensitivity. Sweat can evaporate promptly, maintaining the skin's thermal balance and significantly improving biocompatibility, reducing discomfort from prolonged continuous use. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the electrode structure of the flexible breathable epidermal biosensor described in this invention; Figure 2 This is a schematic diagram of the surface modification pneumatic spraying APTES device described in this invention; Figure 3 This is a schematic diagram of the temperature-controlled screen printing device described in this invention;

[0019] Figure 4 The chronocurrent response curve of the flexible breathable epidermal biosensor described in this invention;

[0020] Figure 5 This is a linear fitting curve of the response current and glucose concentration between the flexible breathable epidermal biosensor described in this invention and a conventional PI sensor.

[0021] In the figure: 1-functionalized electrospun polyimide substrate, 2-Ag wire layer, 3-sensor layer, 4-protective layer, 5-pneumatic spraying device, 6-electrospun polyimide substrate, 7-screen printing template and squeegee, 8-functionalized electrospun polyimide substrate with sensor circuit, 9-temperature control platform. Detailed Implementation

[0022] The flexible, breathable epidermal biosensor of the present invention is described in detail with reference to the embodiments and accompanying drawings, but the present invention is not limited in any way to the content of the embodiments. Unless otherwise specified, the experimental methods described in the embodiments are conventional methods; unless otherwise specified, the experimental reagents and materials are commercially available.

[0023] Example 1 Fabrication of a flexible, breathable epidermal electrochemical glucose sensor like Figure 1 As shown, the flexible, breathable epidermal electrochemical glucose sensor includes an Ag conductor layer 2, a sensor layer 3, and a protective layer 4 on a functionalized electrospun polyimide substrate 1. The entire sensor is fabricated on a surface-functionalized, porous polyimide material 1 that conformally adheres to the human skin epidermis and is used to monitor human blood glucose concentration. The Ag conductor layer 2 and the sensor layer 3 are positioned between the functionalized electrospun polyimide substrate 1 and the protective layer 4. The Ag conductor layer can be connected to external devices. The sensor layer consists of a working electrode, a reference / auxiliary electrode, and an extraction electrode, which can work together under the control of external devices to extract and detect glucose from body fluids (such as sweat, intercellular fluid, etc.). The flexible, breathable epidermal electrochemical glucose sensor is prepared by the following method: (1) Cleaning the substrate: Cut the electrospun polyimide porous material into a suitable size (5×3 cm), use anhydrous ethanol (or organic solution such as acetone) to ultrasonically clean the electrospun polyimide porous material for 15 minutes, and use nitrogen to dry the electrospun polyimide porous material to obtain a clean electrospun polyimide porous material. (2) Plasma activation: The electrospun polyimide porous material was treated with a 300W oxygen plasma machine for 90s to generate hydroxyl groups on its surface, thus obtaining the electrospun polyimide substrate 6.

[0024] (3) Preparation of silane modified solution: After mixing deionized water and ethanol at a mass ratio of 9:1, add acetic acid to adjust the pH of the solution to 5.5, add 3-aminopropyltriethoxysilane at a concentration of 25 wt% to the solution, stir for 2 minutes, and obtain the silane modified solution after the solution becomes clear.

[0025] (4) Silanization-modified spraying: such as Figure 2 As shown, the silane modification solution is loaded into the container of the pneumatic spraying device 5 and sprayed onto the surface of the treated electrospun polyimide substrate 6, which is an electrospun polyimide porous material. The solution is uniformly wetted and subjected to a thermal dehydration condensation reaction at 80°C to form an amino-containing silane network on the surface, thereby achieving substrate surface modification and obtaining a functionalized porous polyimide flexible material. (5) Temperature-controlled screen printing: such as Figure 3 As shown, a functionalized porous polyimide flexible material is fixed on a 35°C temperature-controlled platform 9 using a magnetic suction device. Conductive silver paste, Ag / AgCl electrode ink, and Prussian blue modified carbon ink are then printed sequentially using screen printing. A microstructure conductive electrode pattern is formed using a screen printing template and a squeegee 7. The printed electrodes are then cured at 240°C for 30 minutes to obtain a flexible, breathable epidermal biosensor circuit.

[0026] (6) A chitosan solution containing enzymes and platinum nanoparticles is dropped onto the surface of the working electrode, and a Nafion coating is applied to form a protective layer, thereby obtaining the flexible breathable skin electrochemical glucose sensor.

[0027] During application, after the flexible, breathable epidermal electrochemical glucose sensor is adhered to the skin, glucose concentration can be detected. The detection system here is an electrochemical sensor formed by the reference / auxiliary electrode, working electrode, and extraction electrode in the sensing layer. A constant current (single extraction current density of 150 μA / cm²) is applied to the extraction electrode for a certain period. 2 The extraction time is set to 3 minutes. Epidermal fluid is extracted to the sensor position. A voltage of -0.25V relative to the reference electrode is applied to the working electrode, and a measurement circuit is formed between the working electrode and the auxiliary electrode. Glucose oxidase specifically catalyzes the decomposition of glucose. Under constant potential, the electron transfer rate in the electrochemical reaction, i.e. the current in the electrochemical reaction, is proportional to the glucose concentration in the test solution. The concentration of glucose in the test solution can be obtained by detecting the magnitude of this current.

[0028] Example 2 Performance optimization experiment of the flexible breathable skin electrochemical glucose sensor described in Example 1 The technical advantages of this invention were verified through three sets of key experimental systems. All experiments were conducted in a standard laboratory environment with a temperature of 25±1℃ and a humidity of 45±5%.

[0029] (1) Surface functionalization modification experiment: The effect of APTES concentration on substrate performance was verified by surface functionalization modification experiment. Five groups of modified solutions were prepared (other conditions were the same): APTES concentration: 15wt%, 20wt%, 25wt%, 30wt%, 35wt%. The substrate was treated according to steps (1)-(4) and its contact angle was tested. Then, the same screen printing parameters (400 mesh nylon screen, squeegee pressure 0.3 MPa) were used to print silver conductive patterns with a line width of 500 μm. Next, the substrate to be tested was placed in the tensile platform fixture, with a spacing of 5 cm, and a periodic bending load (amplitude of 0-180°) was applied to the sample at a frequency of 25 Hz to simulate the extreme dynamic deformation in the actual wear scenario.

[0030] Experimental results: Contact angle: decreased from 98.2° (15wt%) to 59.7° (35wt%) with increasing APTES concentration, and remained stable at 63.5-65.4° in the 20-25wt% range; Adhesion: within 650 bending cycles, the 20 wt% APTES group had the lowest resistance drift rate (ΔR / R0<2.8%), significantly better than other concentration groups; Moreover, the failure cycle count was not monotonic with the APTES concentration: below 15 wt%, APTES failed to completely cover the fiber, resulting in the silver layer failing to form a conductive layer on the surface during screen printing; the failure threshold of the 20wt% group reached 607.8±32.0 cycles; in the 25, 30, and 35 wt% groups, excessive cross-linking led to increased substrate brittleness, resulting in stress concentration, which ultimately led to silver layer peeling, and the failure threshold decreased to 361.0±25.0, 174.6±26.0, and 80.0±5.0 cycles, respectively. The optimal concentration of APTES is 20 wt%, which balances hydrophilicity (contact angle <65°), chemical grafting amount, and mechanical durability.

[0031] (2) Temperature-controlled screen printing patterning experiment: To determine the optimal printing temperature, this experiment quantitatively analyzed the effect of temperature on pattern accuracy: using a 20wt% APTES modified substrate, five printing temperatures were set: 25℃, 30℃, 35℃, 40℃, and 45℃, printing patterns with a line width of 50μm (10 samples per group). The test indicators were: line width deviation Δline = |measured value - 50μm| / 50μm, surface roughness Ra (scanned by an ET200 profilometer), and quality factor Q = Δline × Ra. The test results are shown in Table 1.

[0032] Table 1. Effect of printing temperature on electrode quality

[0033] The Q value reaches its lowest value of 18.35 at 35℃, corresponding to the optimal process window. Therefore, the conductive layer prepared at 35℃ has high resolution (12 μm), low roughness (2.3 μm) and excellent electrical stability, providing a key technical guarantee for the reliable integration of wearable sensors.

[0034] (3) Sensor performance comparison experiment: The effect of the process on the overall performance of the sensor was verified by the sensor performance comparison experiment. Six groups of modified APTES substrates and impermeable PI substrates were prepared. The sensors were processed and tested according to Example 1. A constant DC potential (-0.5V) was applied by an electrochemical workstation, and the current was measured at constant time intervals (60s). Glucose solutions of different concentrations (10-100μM) were added dropwise 10 times. Figure 4 As shown, the chronocurrent response curve of the glucose sensor was obtained, and the response current showed a stable upward trend with increasing glucose concentration. Then, through six sets of repeated stepwise experiments, as shown... Figure 5 As shown, a linear fitting curve of the sensor response current versus glucose concentration was obtained. The modified APTES-ePI glucose sensor achieved a sensitivity of 9.888 nA / μM, which is 4.55 times higher than the sensitivity of the same structure impermeable PI substrate (2.175 nA / μM), while the detection limit (S / N=3) was as low as 19.7 μM. The detection performance of this device fully covers the needs of clinical diagnosis, providing reliable technical support for the development of continuous glucose monitoring systems.

[0035] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A flexible, breathable epidermal biosensor, characterized in that: Its flexible substrate is made of functionalized porous polyimide flexible material.

2. The flexible, breathable epidermal biosensor according to claim 1, characterized in that: The thickness of the flexible substrate layer is 10 μm-50 μm.

3. The flexible, breathable epidermal biosensor according to claim 1, characterized in that: From top to bottom, the layers are a flexible substrate layer made of functionalized porous polyimide flexible material, an Ag wire layer, a sensor layer, and a protective layer.

4. The method for manufacturing the flexible breathable epidermal biosensor according to claim 1, characterized in that: Electrochemical sensors are fabricated on porous flexible substrates using surface functionalization units and temperature-controlled screen printing units. The surface functionalization units transform hydrophobic interfaces into hydrophilic interfaces through plasma activation and silanization modification, enhancing ink anchoring capabilities. The temperature-controlled screen printing unit integrates a constant temperature platform and a screen gap fixing mechanism, optimizing ink rheological properties through temperature regulation and suppressing capillary diffusion.

5. The method for manufacturing the flexible breathable epidermal biosensor according to claim 4, characterized in that: It is produced by combining substrate surface functionalization modification with temperature-controlled screen printing. The specific processing steps are as follows: Step S1: Cleaning the substrate: The electrospun polyimide porous material is ultrasonically cleaned with chemical reagents and dried with nitrogen to obtain a clean electrospun polyimide porous material. Step S2: Plasma activation: The electrospun polyimide porous material is treated with oxygen plasma to generate hydroxyl groups on its surface; Step S3: Preparation of silane modified solution: Mix deionized water and ethanol, add acetic acid to adjust the pH of the solution to 4-6, add 3-aminopropyltriethoxysilane at a concentration of 15-35 wt% to the solution, and stir for 2-6 minutes; Step S4: Silane modification spraying: The silane modification solution is sprayed onto the surface of the treated electrospun polyimide porous material using a pneumatic spraying method, and a thermal dehydration reaction is carried out at 50-100℃ to form an amino-containing silane network, thereby modifying the substrate surface and obtaining a functionalized porous polyimide flexible material. Step S5: Temperature-controlled screen printing: The functionalized porous polyimide flexible material is fixed on a heating platform of 25 ℃-65 ℃, and conductive silver paste, Ag / AgCl electrode ink and Prussian blue modified carbon ink are printed sequentially by screen printing to form a microstructure conductive electrode pattern; the printed electrodes are cured at 200-300 ℃ for 30-45 minutes to obtain a flexible breathable epidermal biosensor circuit; Step S6: A chitosan solution containing enzymes and platinum nanoparticles is dropped onto the surface of the working electrode, and a Nafion coating is applied to form a protective layer, thereby obtaining the flexible breathable epidermal biosensor.

6. The method for manufacturing the flexible breathable epidermal biosensor according to claim 5, characterized in that: Oxygen plasma modification of the material surface disrupts its inert chemical layer, transforming it into a hydrophilic hydroxyl interface.

7. The method for manufacturing the flexible breathable epidermal biosensor according to claim 5, characterized in that: The preferred concentration of the 3-aminopropyltriethoxysilane solution is 20 wt%, and it is applied to the material surface using a pneumatic spraying method.

8. The method for manufacturing the flexible breathable epidermal biosensor according to claim 5, characterized in that: The temperature-controlled screen printing module regulates the rheological state of the ink printing by controlling the printing temperature.

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