Gold nanowire-based breathable self-supporting electronic skin and preparation method thereof

Abstract

The invention discloses a breathable self-supporting electronic skin based on gold nanowires and a preparation method of the breathable self-supporting electronic skin, and belongs to the field of flexible electrodes and electronic skins, the electronic skin is composed of a vertically arranged gold nanowire array and has excellent breathability and self-supporting characteristics, and by regulating and controlling the adhesion difference between the gold nanowires and a substrate, the self-supporting performance of the electronic skin is improved. The stable gold nanowire array is achieved, the process is simple and efficient, the material performance is controllable, the gold nanowires are vertically arranged to form a porous structure, the breathability is greatly improved, discomfort caused by long-time wearing is avoided, the requirement for a substrate material is reduced due to the self-supporting characteristic, the fitting degree with the skin is enhanced, and the gold nanowire array can stably work in the complex bending and stretching environment; good biocompatibility is ensured through the stability of the gold nanowires, skin stimulation is avoided, the safety in the fields of health monitoring and biosensing is improved, and the electronic skin is excellent in conductivity, stretchability and comfort, has wide application prospects and is particularly suitable for the fields of wearable equipment and intelligent medical treatment.

Description

Technical Field

[0001] The present invention belongs to the field of flexible electrode technology and electronic skin, and specifically relates to breathable self-supporting electronic skin based on gold nanowires and a preparation method thereof. Background Art

[0002] In recent years, the rapid development of the field of flexible electronic devices has promoted the research and application of electronic skin. Electronic skin is a kind of flexible intelligent device that mimics the functions of human skin and can sense a variety of external stimuli, such as pressure, temperature, humidity and strain. It is widely used in medical health monitoring, wearable devices, human-computer interaction and intelligent robots. However, the performance of existing electronic skin still has many limitations, such as poor air permeability, insufficient mechanical properties and insufficient adaptability in complex application scenarios, which restrict its long-term wear and practical application. Traditional electronic skin usually uses a dense film or elastic substrate as a supporting layer. Although this design can provide a certain mechanical strength, it often sacrifices the air permeability of the material. For wearable sensors that are worn for a long time, poor air permeability can cause discomfort and even skin problems at the wearing site. At the same time, the structural design that relies on the external substrate also limits the lightweight and flexibility of the device.

[0003] As an emerging nanomaterial, gold nanowires have attracted much attention due to their excellent conductivity, chemical stability, stretchability and biocompatibility. The high specific surface area and one-dimensional nanostructure of gold nanowires make them show excellent potential in the fields of sensors, energy devices and flexible electronics. Especially in flexible sensors, gold nanowires can provide highly sensitive electrical responses while having excellent flexibility and stability, and are suitable for various bending, stretching and complex deformation scenarios. However, in the actual application of gold nanowires, they usually need to be based on an external supporting substrate, which limits their advantages in flexibility and permeability. Summary of the invention

[0004] In order to solve the problems raised in the above background technology, the present invention provides a breathable self-supporting electronic skin based on gold nanowires and a preparation method thereof, so as to solve the problems in the prior art of poor biocompatibility and poor air permeability of traditional electronic skin and how to achieve integration with flexible sensors.

[0005] The present invention provides the following technical solutions: The breathable self-supporting electronic skin based on gold nanowires is a gold nanowire film attached to the surface of the skin.

[0006] Preferably, the diameter of the gold nanowires in the gold nanowire film is 5-20 nm and the length is 0.5-2 μm.

[0007] A method for preparing a breathable self-supporting electronic skin based on gold nanowires comprises the following steps: S1: The Si / SiO2 substrate is ultrasonically cleaned using deionized water and isopropanol solution, and then stored in a constant temperature oven; S2: spin coating, printing or spraying a polymethyl methacrylate solution on the cleaned surface of the Si / SiO2 substrate, and performing thermal annealing to obtain a PMMA layer consisting of a polymethyl methacrylate film; S3: spin-coating, printing or spraying a positive photoresist on the thermally annealed polymethyl methacrylate film, exposing and developing the positive photoresist with ultraviolet light and a developer, and then performing secondary thermal annealing to obtain a photoresist layer; S4: After the Si / SiO2 substrate treated in the previous step is subjected to oxygen plasma surface treatment, it is immersed in an anhydrous ethanol solution containing 3-aminopropyltriethoxysilane, or placed in a vacuum oven, octadecyltrichlorosilane is dropped into it and heated; S5: After cleaning with anhydrous ethanol and drying with nitrogen, the Si / SiO2 substrate is immersed in the precursor solution; S6: After washing with deionized water and drying with nitrogen, the Si / SiO2 substrate is immersed in a gold nanowire growth solution to obtain a gold nanowire film consisting of gold nanowires vertically grown on the Si / SiO2 substrate; S7: After cleaning with anhydrous ethanol and drying with nitrogen, the Si / SiO2 substrate and gold nanowires were attached to the skin surface and peeled off after oxygen plasma surface treatment to obtain a breathable self-supporting electronic skin based on gold nanowires; S8: Use gold nanowire electronic skin as electrodes and attach flexible sensor devices to obtain a wearable device based on gold nanowire electronic skin.

[0008] Preferably, in S2, the thermal annealing temperature ranges from 180 to 230° C., and the time ranges from 2 to 10 min.

[0009] Preferably, in S3, the positive photoresist is any one of AZ5214E ​​and AZ1500 series, the secondary thermal annealing temperature ranges from 80-120° C., and the time ranges from 2-15 min.

[0010] Preferably, in S4, the treatment power of the oxygen plasma surface treatment is 100-200 W, the oxygen flow rate is 80-150 ml / min, and the treatment time is 5-10 min.

[0011] Preferably, in S4, when the Si / SiO2 substrate is immersed in an anhydrous ethanol solution containing 3-aminopropyltriethoxysilane, the concentration of 3-aminopropyltriethoxysilane (APTMS) is 5-50 mM, and the immersion time is 2-4 hours. When the Si / SiO2 substrate is placed in a vacuum oven, octadecyltrichlorosilane is dropped and heated, the heating temperature is 80-150°C, and the heating time is 2-4 hours.

[0012] Preferably, in S5, the precursor solution is obtained by reacting a chloroauric acid solution with a weak reducing agent, sodium citrate, and a strong reducing agent, sodium borohydride. The concentration of chloroauric acid in the precursor solution is 0.25-0.8 mM, the concentration of sodium citrate is 0.25-0.8 mM, the concentration of sodium borohydride is 3-10 mM, and the immersion time in the precursor solution is 2-4 hours.

[0013] Preferably, in S6, the concentration of chloroauric acid in the gold nanowire growth solution is 6.9-12 mM, the concentration of 4-mercaptobenzoic acid is 1.1-3.3 mM, the concentration of L-ascorbic acid is 16.4-30 mM, and the immersion time in the gold nanowire growth solution is 1-2 hours.

[0014] The beneficial effects of the present invention are: 1. The process is simple and can be prepared on a large scale at room temperature.

[0015] 2. The breathable self-supporting electronic skin based on gold nanowires does not require an additional substrate as a supporting layer, achieving a high degree of fit between the electrode and the human skin, and can more freely adapt to deformations such as bending, stretching and twisting.

[0016] 3. Due to the overall porous structure of the gold nanowire film, the electronic skin has excellent breathability, avoiding the stuffiness or skin discomfort caused by traditional substrates, and maintaining stable performance even during dynamic movement.

[0017] 4. High conductivity and sensitivity: The excellent conductivity of gold nanowires ensures the high sensitivity of electronic skin to collect physiological signals.

[0018] 5. Good biocompatibility: Since gold itself has excellent redox inertness, electronic skin based on gold nanowires has excellent stability and good biocompatibility and is suitable for long-term wear.

[0019] 6. Multifunctional integration: Electronic skin based on gold nanowires can combine multiple sensing modules to provide comprehensive health monitoring and interactive functions. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the structure of this application; Figure 2Schematic diagram of peeling the electronic skin from the Si / SiO2 substrate and attaching it to human skin; Figure 3 Transfer characteristic curve for attaching organic electrochemical transistors on gold nanowire breathable self-supporting electronic skin to detect human glucose content; Figure 4 This is a scanning electron microscope image of a porous gold nanowire film grown vertically on a Si / SiO2 substrate; The markings in the figure are: Gold nanowire film-1; photoresist layer-2; polymethyl methacrylate (PMMA) layer-3; Si / SiO2 substrate-4. DETAILED DESCRIPTION

[0021] In order to facilitate those skilled in the art to understand the technical content of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific examples. It should be understood that the specific examples described herein are only used to explain the present invention and are not used to limit the present invention.

[0022] The concentration unit mM used in this application is an abbreviation for millimole per liter.

[0023] Example 1 (control group) Step (1): ultrasonically clean and dry the Si / SiO2 substrate 4 with isopropyl alcohol, and perform surface treatment on the Si / SiO2 substrate 4 for 15 minutes using an ultraviolet ozone cleaning machine; Step (2): Spin-coating polymethyl methacrylate (950, A6) on the wafer surface of the Si / SiO2 substrate 4 at 3000 rpm / s, and annealing at 180° C. for 2 minutes to obtain a PMMA layer 3 composed of a polymethyl methacrylate film; Step (3): after spin coating the positive photoresist AZ5214E ​​on the surface of the polymethyl methacrylate film at 3000 rpm / s, secondary annealing is performed at 110° C. for 2 minutes to obtain a photoresist layer 2; Step (4): patterning is performed on AZ5214E ​​using a standard photolithography process. Specifically, after covering AZ5214E ​​with a photolithography mask, a 300W, 365nm ultraviolet lamp is used to irradiate for 10 seconds. After exposure, the Si / SiO2 substrate 4 is immersed in a developer (MIF300) for 30 seconds, and then immersed in deionized water for another 30 seconds to obtain a patterned area. Step (5): After the Si / SiO2 substrate 4 is subjected to plasma treatment for 5 minutes, it is immersed in a 5 mM APTMS solution for 2 hours and then rinsed with anhydrous ethanol and nitrogen; Step (6): soak the cleaned Si / SiO2 substrate 4 in a precursor solution having a chloroauric acid concentration of 0.3 mM, a sodium citrate concentration of 0.25 mM, and a sodium borohydride concentration of 8 mM for 2 hours, and then rinse with deionized water and nitrogen gas; Step (7): soaking the cleaned Si / SiO2 substrate 4 in a gold nanowire growth solution having a chloroauric acid concentration of 12 mM, a 4-mercaptobenzoic acid concentration of 1.1 mM, and an L-ascorbic acid concentration of 30 mM for 5 minutes, and then flushing with anhydrous ethanol and nitrogen to obtain a gold nanowire film 1 consisting of gold nanowires vertically grown on the Si / SiO2 substrate 4; Step (8): After 5 minutes of oxygen plasma surface treatment, the Si / SiO2 substrate 4 containing gold nanowires is attached to the elbow joint of the human body to obtain a self-supporting electronic skin based on gold nanowires. A flexible electrochemical sensor is attached to the surface of the electronic skin to analyze the glucose content in human sweat. The obtained transfer characteristic curve is as follows: Figure 3 shown.

[0024] Embodiment 2: The difference from Example 1 is that in step (2), polymethyl methacrylate is spin-coated on the surface of the Si / SiO2 wafer at 2000 rpm / s.

[0025] Embodiment 3: The difference from Example 1 is that in step (2), polymethyl methacrylate is spin-coated on the surface of the Si / SiO2 wafer at 4000 rpm / s.

[0026] Embodiment 4: The difference from Example 1 is that in step (6), the concentration of chloroauric acid in the precursor solution is 0.6 mM, the concentration of sodium citrate is 0.5 mM, and the concentration of sodium borohydride is 16 mM.

[0027] Embodiment 5: The difference from Example 1 is that in step (6), the concentration of chloroauric acid in the precursor solution is 0.9 mM, the concentration of sodium citrate is 0.75 mM, and the concentration of sodium borohydride is 24 mM.

[0028] Embodiment 6: The difference from Example 1 is that in step (7), the concentration of chloroauric acid in the gold nanowire growth solution is 6 mM, the concentration of 4-mercaptobenzoic acid is 0.55 mM, and the concentration of L-ascorbic acid is 15 mM.

[0029] Embodiment 7: The difference from Example 1 is that in step (7), the concentration of chloroauric acid in the gold nanowire growth solution is 24 mM, the concentration of 4-mercaptobenzoic acid is 2.2 mM, and the concentration of L-ascorbic acid is 60 mM.

[0030] The test results of the gold nanowire breathable self-supporting electronic skin of Examples 1-7 are shown in Table 1.

[0031]

[0032] Table 1 It can be seen that: by comparing Examples 1-3 respectively, the adhesion of the self-supporting gold nanowire electronic skin to the surface of human skin is related to the spin coating speed of polymethyl methacrylate (PMMA). When the spin coating speed is too fast, the surface adhesion deteriorates, and the gold nanowires fall off the human body surface. The optimal spin coating speed is 3000rpm / s. Comparing Example 1 and Examples 4-7, the concentration of the precursor solution will change the diameter of the gold seed, and the concentration of the gold nanowire growth solution will change the diameter and length of the nanowire. As a result, the resistance will change significantly under large-range bending conditions. The optimal precursor solution concentration is: 0.3mM chloroauric acid, 0.25mM sodium citrate, and 8mM sodium borohydride; the optimal gold nanowire growth solution concentration is: 12mM chloroauric acid, 1.1mM 4-mercaptobenzoic acid, and 30mM L-ascorbic acid. At the same time, the air permeability test of the gold nanowire electronic skin in different embodiments was carried out. As a preferred embodiment, Figure 4 It can be seen from the SEM image that the porous gold nanowires prepared by the concentration of the precursor solution and the concentration of the gold nanowire growth solution in Example 1 have stable resistance and strain adaptability, taking into account the conductivity characteristics and air permeability of the electronic skin.

[0033] The present invention has been described through the above embodiments, but it should be understood that the above embodiments are only for the purpose of example and description, and are not intended to limit the present invention to the scope of the described embodiments. In addition, it can be understood by those skilled in the art that the present invention is not limited to the above embodiments, and more variations and modifications can be made according to the teachings of the present invention, and these variations and modifications all fall within the scope of the protection claimed by the present invention.

Claims

1. Breathable self-supporting electronic skin based on gold nanowires, characterized in that It is a gold nanowire film (1) attached to the surface of the skin.

2. The breathable self-supporting electronic skin based on gold nanowires according to claim 1, characterized in that: The diameter of the gold nanowires in the gold nanowire film (1) is 5-20 nm and the length is 0.5-2 μm.

3. The method for preparing a breathable self-supporting electronic skin based on gold nanowires according to any one of claims 1 to 2, characterized in that: The following steps are involved: S1: ultrasonically clean the Si / SiO2 substrate (4) using deionized water and isopropanol solution, and store it in a constant temperature oven after cleaning; S2: spin coating, printing or spraying a polymethyl methacrylate solution on the cleaned surface of the Si / SiO2 substrate (4), and performing thermal annealing to obtain a PMMA layer (3) composed of a polymethyl methacrylate film; S3: spin coating, printing or spraying a positive photoresist on the thermally annealed polymethyl methacrylate film, exposing and developing the positive photoresist with ultraviolet light and a developer, and then performing secondary thermal annealing to obtain a photoresist layer (2); S4: After the Si / SiO2 substrate (4) treated in the previous step is subjected to oxygen plasma surface treatment, it is immersed in an anhydrous ethanol solution containing 3-aminopropyltriethoxysilane, or placed in a vacuum oven, octadecyltrichlorosilane is dropped into it and heated; S5: After cleaning with anhydrous ethanol and drying with nitrogen, the Si / SiO2 substrate (4) is immersed in the precursor solution; S6: After washing with deionized water and drying with nitrogen, the Si / SiO2 substrate (4) is immersed in a gold nanowire growth solution to obtain a gold nanowire film (1) consisting of gold nanowires vertically grown on the Si / SiO2 substrate (4); S7: After washing with anhydrous ethanol and drying with nitrogen, the Si / SiO2 substrate (4) and the gold nanowires are attached to the skin surface and peeled off after oxygen plasma surface treatment to obtain a breathable self-supporting electronic skin based on gold nanowires; S8: Use gold nanowire electronic skin as electrodes and attach flexible sensor devices to obtain a wearable device based on gold nanowire electronic skin.

4. The method for preparing a breathable self-supporting electronic skin based on gold nanowires according to claim 3, characterized in that: In S2, the thermal annealing temperature ranges from 180 to 230°C and the time ranges from 2 to 10 minutes.

5. The method for preparing a breathable self-supporting electronic skin based on gold nanowires according to claim 3, characterized in that: In S3, the positive photoresist is any one of the AZ5214E ​​and AZ1500 series, the secondary thermal annealing temperature ranges from 80 to 120° C., and the time ranges from 2 to 15 min.

6. The method for preparing a breathable self-supporting electronic skin based on gold nanowires according to claim 3, characterized in that: In S4, the treatment power of the oxygen plasma surface treatment is 100-200 W, the oxygen flow rate is 80-150 ml / min, and the treatment time is 5-10 min.

7. The method for preparing a breathable self-supporting electronic skin based on gold nanowires according to claim 3, characterized in that: In S4, when the Si / SiO2 substrate (4) is immersed in an anhydrous ethanol solution containing 3-aminopropyltriethoxysilane, the concentration of 3-aminopropyltriethoxysilane (APTMS) is 5-50 mM, and the immersion time is 2-4 hours. When the Si / SiO2 substrate (4) is placed in a vacuum oven, octadecyltrichlorosilane is dropped into it and heated, the heating temperature is 80-150°C, and the heating time is 2-4 hours.

8. The method for preparing a breathable self-supporting electronic skin based on gold nanowires according to claim 3, characterized in that: In S5, the precursor solution is obtained by reacting a chloroauric acid solution with a weak reducing agent, sodium citrate, and a strong reducing agent, sodium borohydride. The concentration of chloroauric acid in the precursor solution is 0.25-0.8 mM, the concentration of sodium citrate is 0.25-0.8 mM, and the concentration of sodium borohydride is 3-10 mM. The immersion time in the precursor solution is 2-4 hours.

9. The method for preparing a breathable self-supporting electronic skin based on gold nanowires according to claim 3, characterized in that: In S6, the concentration of chloroauric acid in the gold nanowire growth solution is 6.9-12 mM, the concentration of 4-mercaptobenzoic acid is 1.1-3.3 mM, and the concentration of L-ascorbic acid is 16.4-30 mM. The immersion time in the gold nanowire growth solution is 1-2 hours.

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