Adjustable electronic skin sensing ink as well as preparation method and application thereof
By preparing electronic skin sensing inks with core-shell structured composite nanoparticles, the problems of stability and single sensing mode of metal nanoparticle inks in electronic skin applications have been solved, achieving adjustable performance and reduced cost.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-03
- Publication Date
- 2026-03-24
AI Technical Summary
Existing metal nanoparticle inks suffer from poor long-term stability, fragile mechanical properties, and limited sensing modes in high-performance electronic skin applications, making it difficult to improve long-term stability and achieve programmable control of sensing performance.
By using core-shell structured composite nanoparticles, with metal nanoparticles as the core and copolymerized polymer monomers as the shell, electronic skin sensing inks suitable for different sensing needs can be prepared by controlling the shell thickness and crosslinking density.
The oxidation and aggregation of silver nanoparticles were inhibited, improving the long-term stability and mechanical properties of the ink, meeting the needs of high-sensitivity pressure sensing and wide-range tensile sensing, and reducing production costs.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of flexible electronic functional materials, specifically to an adjustable electronic skin-sensing ink, its preparation method, and its application. Background Technology
[0002] Electronic skin, a flexible sensing system that mimics human skin's ability to perceive external stimuli (such as pressure, tension, and temperature), is a core technology driving the development of next-generation human-computer interaction, health monitoring, intelligent robots, and wearable devices. One of the key materials for realizing the sensing function of electronic skin is conductive ink, which needs to possess excellent conductivity, good mechanical flexibility, environmental stability, and customizable sensing performance. Metal nanoparticle inks (especially silver nanoparticle (AgNPs) inks) have become a research hotspot due to their extremely high conductivity, relatively low cost, and mature synthesis processes.
[0003] However, existing metal nanoparticle inks face several bottlenecks that urgently need to be addressed when applying them to high-performance electronic skin applications: 1. Long-term stability challenges: Nanoparticles have extremely high surface energy, making them highly susceptible to oxidation and aggregation, especially under hot and humid environments. This leads to increased ink resistivity, performance degradation, and even failure; silver nanoparticles are more prone to oxidation than gold nanoparticles, making this problem particularly pronounced. 2. Limited mechanical properties and sensing modes: The conductive film formed after curing traditional inks is usually brittle and prone to cracking under repeated stretching or bending, resulting in irreversible breakage of the conductive pathway. Its resistance change mode is limited, making it difficult to achieve both high-sensitivity micro-pressure sensing and high-strain tensile sensing using the same technology platform. 3. Poor performance adjustability: Existing technologies typically introduce polymers through physical blending or simple encapsulation, making it difficult to precisely control key parameters such as the thickness of the encapsulation layer and crosslinking density. This prevents the ink's final performance from being "designed on demand," limiting its application range.
[0004] Currently, there is a lack of a universal solution that can precisely control the structure of the encapsulation layer at the molecular level, thereby simultaneously achieving improved long-term stability and programmable sensing performance. Summary of the Invention
[0005] To overcome the shortcomings of the prior art, the present invention provides an adjustable electronic skin-sensing ink, its preparation method, and its application. The specific technical solution is as follows: A method for preparing an adjustable electronic skin sensing ink, wherein the active ingredient of the electronic skin sensing ink is a core-shell structured composite nanoparticle; wherein the core structure of the core-shell structured composite nanoparticle is a metal nanoparticle; and the shell structure of the core-shell structured composite nanoparticle is a copolymerized polymer monomer; specifically including the following steps: S1. Synthesis and pretreatment of metal nanonuclei; S2. Preparation of aqueous dispersion of copolymer polymer monomers; S3. Surface initiation and polymerization reaction; S4. Post-reaction processing to obtain electronic skin sensing ink.
[0006] Preferably, the metal ions in the metal nanoparticles are silver ions.
[0007] Preferably, the synthesis and pretreatment of the metal nanonucleus in S1 specifically includes the following sub-steps: S1.1 The sodium citrate reduction method was used. Under boiling conditions, the solution of trisodium citrate dihydrate was added to a three-necked flask containing silver nitrate solution and stirred at a speed of 300-600 rpm. After the reaction was carried out for 30-50 min, it was cooled to room temperature to synthesize silver nanoparticle hydrosol. S1.2 Centrifuge the silver nanoparticle hydrosol at 3000-5000 rpm for 5-10 min, collect the silver nanoparticle dispersion and store it at 4℃. S1.3 Take 5-10 mL of a silver nanoparticle dispersion with a concentration of 50-100 nM and add 0.05-0.1 g of sodium dodecyl sulfate solid for surface pretreatment.
[0008] Preferably, the volume of the silver nitrate solution is 95-100 mL and the concentration is 0.5-1.0 mM; the volume of the trisodium citrate dihydrate solution is 5-7 mL and the concentration is 17-22 mM.
[0009] Preferably, the preparation of the copolymer monomer aqueous dispersion in step S2 specifically includes: mixing the main monomer, functional monomer, and crosslinking agent monomer in a mass ratio of 65:33:5 and dissolving them in 4-6 mL of water to obtain the copolymer monomer aqueous dispersion; wherein, the main monomer is methyl methacrylate with a mass concentration of 60-70 wt%; the functional monomer is either methacrylic acid or 2-carboxyethyl acrylate with a mass concentration of 28-35 wt%; and the crosslinking agent monomer is ethylene glycol dimethacrylate with a mass concentration of 2-12 wt%.
[0010] Preferably, the surface initiation and polymerization reaction described in S3 specifically includes the following sub-steps: S3.1 Take 15-25 mL of the surface-pretreated solution from S1.3 and place it in a three-necked flask. Purge nitrogen gas while stirring magnetically to remove oxygen from the solution, and then heat to 75-80℃. S3.2 Add 120–160 μL of 0.8–1.2 M buffer salt solution to the three-necked flask and adjust the pH of the solution to 5.0–6.0; then add 90–110 μL of 17–22 mM initiator solution. S3.3 Take 30-40 mL of the aqueous dispersion of the copolymerized polymer obtained in S2 and add it dropwise to the mixture obtained in S3.2 at a rate of 0.7-0.9 mL / min using a syringe pump. The dropwise addition will be completed in 0.5-1 h.
[0011] Preferably, the buffer salt solution is a K2HPO4 solution; the initiator solution is an ammonium persulfate solution or a C6H2O solution. 13 One of the NO4S buffer solutions.
[0012] More preferably, the post-reaction treatment described in S4 to obtain the electronic skin sensing ink specifically involves: after the aqueous dispersion of the copolymer polymer monomer is added dropwise, the reaction continues for 3-4 hours, followed by natural cooling to room temperature; centrifugation is performed at 3000-5000 rpm for 10-15 minutes to obtain the final product composed of core-shell structured composite nanoparticles; the final product composed of core-shell structured composite nanoparticles is redispersed in water at a volume ratio of final product to water of 1:4 to form a stable electronic skin sensing ink.
[0013] An adjustable electronic skin-sensing ink is prepared by the above-described preparation method; the shell structure thickness of the core-shell composite nanoparticles is 10–20 nm.
[0014] An application of an adjustable electronic skin sensing ink, using the aforementioned electronic skin sensing ink to prepare an electronic skin sensor, wherein the electronic skin sensor is made by coating or printing the electronic skin sensing ink onto a flexible substrate: When the functional monomer is methacrylic acid and its mass ratio in the copolymer monomer is greater than 30 wt%, and the mass ratio of the crosslinking agent in the copolymer monomer is greater than 2 wt%, the electronic skin sensor is suitable for high-sensitivity pressure sensing. When the functional monomer is 2-carboxyethyl acrylate and its mass ratio in the copolymer monomer is higher than 50 wt%, and the mass ratio of the crosslinking agent in the copolymer monomer is lower than 2 wt%, the electronic skin sensor is suitable for a wide range of stretch sensing and motion capture.
[0015] The beneficial effects of this invention are: 1. The dense polymer shell of this invention effectively isolates oxygen and moisture, significantly inhibits the oxidation of silver nanoparticles and the aggregation of all nanoparticles, and the ink has a shelf life of more than 6 months. 2. This invention utilizes a basic preparation process to generate various specialized inks by adjusting the formulation parameters, thereby achieving the adjustment of ink performance. Specifically, a high cross-linking degree formulation produces a high-modulus shell layer, suitable for pressure sensing; a low cross-linking degree and highly flexible monomer formulation produces a low-modulus shell layer, suitable for tensile sensing. This effectively meets the needs of different sensing dimensions of electronic skin and reduces research and development and production costs. Detailed Implementation
[0016] To overcome the shortcomings of the prior art, the present invention provides an adjustable electronic skin-sensing ink, its preparation method, and its application. The specific technical solution is as follows: A method for preparing an adjustable electronic skin sensing ink, wherein the active ingredient of the electronic skin sensing ink is a core-shell structured composite nanoparticle; wherein the core structure of the core-shell structured composite nanoparticle is a metal nanoparticle; preferably, the metal ions in the metal nanoparticle are silver ions. The shell structure of the core-shell structured composite nanoparticle is a copolymer polymer monomer.
[0017] The preparation method specifically includes the following steps: S1. Synthesis and pretreatment of metal nanonuclei, specifically including the following sub-steps: S1.1 The sodium citrate reduction method was used. Under boiling conditions, the trisodium citrate dihydrate solution was added to a three-necked flask containing silver nitrate solution and stirred vigorously at a speed of 300-600 rpm. After the reaction was carried out for 30-50 minutes, it was cooled to room temperature to synthesize silver nanoparticle hydrosol. S1.2 Centrifuge the silver nanoparticle hydrosol at 3000-5000 rpm for 5-10 min, collect the silver nanoparticle dispersion and store it at 4℃. S1.3 Take 5-10 mL of a silver nanoparticle dispersion with a concentration of 50-100 nM and add 0.05-0.1 g of sodium dodecyl sulfate solid for surface pretreatment.
[0018] Preferably, the volume of the silver nitrate solution is 95-100 mL and the concentration is 0.5-1.0 mM; the volume of the trisodium citrate dihydrate solution is 5-7 mL and the concentration is 17-22 mM.
[0019] S2. Preparation of an aqueous dispersion of the copolymerized polymer monomer, specifically including: The main monomer, functional monomer, and crosslinking agent monomer are mixed at a mass ratio of 65:33:5 and dissolved in 4-6 mL of water to obtain an aqueous dispersion of the copolymer monomer; wherein the main monomer is methyl methacrylate (MMA) with a mass concentration of 60-70 wt%; the functional monomer is either methacrylic acid (MAA) or 2-carboxyethyl acrylate (CEA) with a mass concentration of 28-35 wt%; and the crosslinking agent monomer is ethylene glycol dimethacrylate (EGDMA) with a mass concentration of 2-12 wt%.
[0020] S3. Surface initiation and polymerization reaction, specifically including the following sub-steps: S3.1 Take 15-25 mL of the surface-pretreated solution from S1.3 and place it in a three-necked flask. Purge nitrogen gas while stirring magnetically to remove oxygen from the solution, and then heat to 75-80℃. S3.2 Add 120–160 μL of 0.8–1.2 M buffer salt solution to the three-necked flask and adjust the pH of the solution to 5.0–6.0; then add 90–110 μL of 17–22 mM initiator solution. S3.3 Take 30-40 mL of the aqueous dispersion of the copolymerized polymer obtained in S2 and add it dropwise to the mixture obtained in S3.2 at a rate of 0.7-0.9 mL / min using a syringe pump. The dropwise addition will be completed in 0.5-1 h.
[0021] Preferably, the buffer salt solution is a K2HPO4 solution; the initiator solution is an ammonium persulfate solution (APS) or a C6H2O solution. 13 One of the NO4S buffer solutions.
[0022] S4. Post-reaction processing to obtain electronic skin-sensing ink, specifically: After the aqueous dispersion of the copolymer polymer monomers is added dropwise, the reaction continues for 3-4 hours, and then it is naturally cooled to room temperature. The final product composed of core-shell structured composite nanoparticles is obtained by centrifugation at 3000-5000 rpm for 10-15 minutes. By redispersing the final product, which consists of core-shell composite nanoparticles, in water at a volume ratio of 1:4, a stable electronic skin sensing ink can be formed.
[0023] An adjustable electronic skin-sensing ink is prepared by the above-described method; it is worth noting that the shell structure thickness of the core-shell composite nanoparticles is 10–20 nm.
[0024] An application of an adjustable electronic skin sensing ink, using the aforementioned electronic skin sensing ink to prepare an electronic skin sensor, wherein the electronic skin sensor is made by coating or printing the electronic skin sensing ink onto a flexible substrate: When the functional monomer is methacrylic acid and its mass ratio in the copolymer monomer is greater than 30 wt%, and the mass ratio of the crosslinking agent in the copolymer monomer is greater than 2 wt%, the electronic skin sensor is suitable for high-sensitivity pressure sensing. When the functional monomer is 2-carboxyethyl acrylate and its mass ratio in the copolymer monomer is higher than 50 wt%, and the mass ratio of the crosslinking agent in the copolymer monomer is lower than 2 wt%, the electronic skin sensor is suitable for a wide range of stretch sensing and motion capture.
[0025] It is worth noting that the flexible substrate includes, but is not limited to, polyimide (PI) film, polydimethylsiloxane (PDMS) film, polyethylene terephthalate (PET) film, polyurethane (PU), biodegradable substrate, hydrogel substrate, 3D sponge substrate, or fabric or natural material substrate, etc., and is not intended to further limit the present invention.
[0026] The invention will be further described below with reference to specific embodiments 1-2 and comparative examples 1-2: Example 1: Synthesis of highly crosslinked silver-based inks (Ag-MAA15 NPs) suitable for pressure sensing; Synthesis and pretreatment of S1.Ag NPs: The Turkevich method was used to synthesize Ag NPs sol by adding sodium citrate solution to boiling silver nitrate solution and cooling to room temperature after the reaction. The Ag NPs sol was centrifuged and washed, and 10.0 mL of Ag NPs dispersion with a concentration of 3.2 nM was collected. Sodium dodecyl sulfate was added for surface pretreatment.
[0027] S2. Preparation of copolymer monomer dispersion: Weigh out 50 mg of MMA (65.0 wt%), MAA (33.0 wt%) and EGDMA (2.0 wt%) and dissolve them in 5 mL of water.
[0028] S3. Surface initiation and polymerization reaction: Take 20 mL of the pretreated Ag NPs dispersion and place it in a three-necked flask. Purge with nitrogen while stirring magnetically to remove oxygen from the solution, and then heat to 80 °C. Then add 140 μL of 1.0 M K2HPO4 solution (adjust pH ≈ 5.5) to the three-necked flask, followed by 100 μL of 20 mM APS solution. Use a syringe pump to add the copolymer monomer dispersion dropwise at a rate of 0.08 mL / min, and complete the addition in 1 hour.
[0029] S4. Post-reaction treatment: The reaction was continued for 3 hours, cooled to room temperature and centrifuged. The resulting final product was labeled Ag-MAA15.
[0030] Example 2: Synthesis of low crosslinking silver-based inks (Ag-CEA3 NPs) suitable for motion capture: S1. Ag NPs synthesis and pretreatment are the same as in Example 1; S2. Preparation of copolymer monomer dispersion: Weigh out 60 mg of MMA (45.2 wt%), CEA (53.2 wt%) and EGDMA (1.6 wt%) and dissolve them in 5 mL of water.
[0031] S3. Surface initiation and polymerization reaction: Take 20 mL of the pretreated Ag NPs dispersion and place it in a three-necked flask. Purge with nitrogen while stirring magnetically to remove oxygen from the solution, and then heat to 80 °C. Then add 120 μL of 1.0 M K2HPO4 solution to the three-necked flask (adjust pH ≈ 5.3), followed by 100 μL of 20 mM APS solution. Use a syringe pump to add the copolymer monomer dispersion dropwise at a rate of 0.08 mL / min, and complete the addition in 1 hour.
[0032] S4. The post-reaction treatment is the same as in Example 1, and the resulting final product is labeled as Ag-CEA3.
[0033] Comparative Example 1: Synthesis of gold nanoparticle-based pressure sensing ink (Au-MAA15 NPs); The preparation steps were exactly the same as in Example 1, except that the silver ions in the metal nanoparticles were replaced with pretreated gold nanoparticles (Au NPs, concentration 2.97 nM), and the resulting final product was labeled Au-MAA15.
[0034] Comparative Example 2: Synthesis of silver-based inks (Ag-MAA10 NPs) with moderate performance; The preparation steps were similar to those in Example 1, except that the proportions of the copolymer monomers were adjusted to: MMA (78.0 wt%), MAA (20.0 wt%) and EGDMA (2.0 wt%), and the amount of K2HPO4 added was changed to 100 μL (to adjust the pH to approximately 5.6). The final product was labeled as Ag-MAA10.
[0035] The resistive sensors fabricated using Examples 1-2 and Comparative Examples 1-2 were subjected to performance tests, and the results are detailed in Table 1 below: In summary, this invention enables the preparation of a series of inks (Ag-MAA15, Ag-CEA3, Ag-MAA10, etc.) with silver nanoparticles as the core, and their performance can be precisely controlled through formulation parameters. Comparing Ag-MAA15 and Au-MAA15, their pressure sensing performance is similar, thus proving that this invention can replace gold ions with silver ions at a lower cost, while the silver core is effectively protected by a polymer shell. In addition, the low crosslinking degree silver-based ink Ag-CEA3 exhibits excellent tensile properties, fully meeting the requirements of motion capture. Furthermore, the performance of Comparative Example 2 further confirms that continuous and controllable performance changes can be achieved by adjusting the mass ratio of MAA.
[0036] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.
Claims
1. A method for preparing an adjustable electronic skin-sensing ink, characterized in that, The active ingredient of the electronic skin sensing ink is a core-shell structured composite nanoparticle; wherein, the core structure of the core-shell structured composite nanoparticle is a metal nanoparticle; and the shell structure of the core-shell structured composite nanoparticle is a copolymer polymer monomer. Specifically, the following steps are included: S1. Synthesis and pretreatment of metal nanonuclei; S2. Preparation of aqueous dispersion of copolymerized polymer monomers; S3. Surface initiation and polymerization reaction; S4. Post-reaction processing to obtain electronic skin sensing ink.
2. The method for preparing the adjustable electronic skin-sensing ink according to claim 1, characterized in that, The metal ions in the metal nanoparticles are silver ions.
3. The method for preparing the adjustable electronic skin-sensing ink according to claim 2, characterized in that, The synthesis and pretreatment of the metal nanonuclei described in S1 specifically includes the following sub-steps: S1.1 The sodium citrate reduction method was used. Under boiling conditions, the solution of trisodium citrate dihydrate was added to a three-necked flask containing silver nitrate solution and stirred at a speed of 300-600 rpm. After the reaction was carried out for 30-50 min, it was cooled to room temperature to synthesize silver nanoparticle hydrosol. S1.2 Centrifuge the silver nanoparticle hydrosol at 3000-5000 rpm for 5-10 min, collect the silver nanoparticle dispersion and store it at 4℃. S1.3 Take 5-10 mL of a silver nanoparticle dispersion with a concentration of 50-100 nM and add 0.05-0.1 g of sodium dodecyl sulfate solid for surface pretreatment.
4. The method for preparing the adjustable electronic skin-sensing ink according to claim 3, characterized in that, The silver nitrate solution has a volume of 95–100 mL and a concentration of 0.5–1.0 mM. The volume of the trisodium citrate dihydrate solution is 5–7 ml; the concentration is 17–22 mM.
5. The method for preparing the adjustable electronic skin-sensing ink according to claim 4, characterized in that, The preparation of the copolymer polymer monomer aqueous dispersion described in S2 specifically includes: The main monomer, functional monomer and crosslinking agent monomer are mixed in a mass ratio of 65:33:5 and dissolved in 4-6 mL of water to obtain an aqueous dispersion of the copolymer polymer monomer. The main monomer is methyl methacrylate with a mass concentration of 60-70 wt%; the functional monomer is either methacrylic acid or 2-carboxyethyl acrylate with a mass concentration of 28-35 wt%; and the crosslinking agent monomer is ethylene glycol dimethacrylate with a mass concentration of 2-12 wt%.
6. The method for preparing the adjustable electronic skin-sensing ink according to claim 5, characterized in that, The surface initiation and polymerization reaction described in S3 specifically includes the following sub-steps: S3.1 Take 15-25 mL of the surface-pretreated solution from S1.3 and place it in a three-necked flask. Purge nitrogen gas while stirring magnetically to remove oxygen from the solution, and then heat to 75-80℃. S3.2 Add 120–160 μL of 0.8–1.2 M buffer salt solution to the three-necked flask and adjust the pH of the solution to 5.0–6.0; then add 90–110 μL of 17–22 mM initiator solution. S3.3 Take 30-40 mL of the aqueous dispersion of the copolymerized polymer obtained in S2 and add it dropwise to the mixture obtained in S3.2 at a rate of 0.7-0.9 mL / min using a syringe pump. The dropwise addition will be completed in 0.5-1 h.
7. The method for preparing the adjustable electronic skin-sensing ink according to claim 5, characterized in that, The buffer salt solution used is a K2HPO4 solution; The initiator solution is an ammonium persulfate solution or a C6H solution. 13 One of the NO4S buffer solutions.
8. The method for preparing the adjustable electronic skin-sensing ink according to claim 6, characterized in that, The post-reaction processing described in S4 yields the electronic skin-sensing ink, specifically as follows: After the aqueous dispersion of the copolymer polymer monomers is added dropwise, the reaction continues for 3-4 hours, and then it is naturally cooled to room temperature. The final product composed of core-shell structured composite nanoparticles is obtained by centrifugation at 3000-5000 rpm for 10-15 minutes. By redispersing the final product, which consists of core-shell composite nanoparticles, in water at a volume ratio of 1:4, a stable electronic skin sensing ink can be formed.
9. An adjustable electronic skin-sensing ink, characterized in that, It is prepared by the method of preparing the adjustable electronic skin sensing ink according to claim 8; The shell structure thickness of the core-shell composite nanoparticles is 10–20 nm.
10. An application of an adjustable electronic skin sensing ink, employing the electronic skin sensing ink of claim 9, characterized in that, For fabricating electronic skin sensors, the electronic skin sensors are made by coating or printing electronic skin sensing ink onto a flexible substrate: When the functional monomer is methacrylic acid and its mass ratio in the copolymer monomer is greater than 30 wt%, and the mass ratio of the crosslinking agent in the copolymer monomer is greater than 2 wt%, the electronic skin sensor is suitable for high-sensitivity pressure sensing. When the functional monomer is 2-carboxyethyl acrylate and its mass ratio in the copolymer monomer is higher than 50 wt%, and the mass ratio of the crosslinking agent in the copolymer monomer is lower than 2 wt%, the electronic skin sensor is suitable for a wide range of stretch sensing and motion capture.