A hydrogel-based ultrastretchable flexible multifunctional input device and preparation and application thereof

Abstract

This invention discloses a hydrogel-based ultra-stretchable flexible multifunctional input device, its preparation, and its application. Based on a dual-crosslinking synthesis strategy involving hydrophilic polymer chains through hydrophobic crosslinking nodes and liquid metal electrostatic crosslinking nodes, this invention synthesizes conductive hydrogels using gamma-ray or electron beam radiation-induced polymerization and crosslinking methods, and successfully applies them to flexible multifunctional input devices. This device exhibits ultra-high tensile strength and self-healing properties, capable of withstanding significant cyclic stretching, achieving self-healing after repeated damage, and maintaining normal operation under certain stretching amplitudes and after self-healing. The device can function as both a touchscreen and a sensor, and can switch between these functions, offering advantages such as versatility, high sensitivity, and durability, and has broad application prospects in stretchable flexible electronic devices.

Description

Technical Field

[0001] This invention relates to flexible multifunctional input devices, specifically to a flexible touchscreen and sensor assembled from ultra-tensile conductive hydrogel, as well as its preparation method and application fields. Background Technology

[0002] Wearable electronic devices have wide applications in emerging fields such as human-computer interaction, smart entertainment, motion monitoring, and smart healthcare. With the development of wearable electronic devices, the requirements for the sensitivity, functionality, and deformation resistance of flexible input devices are gradually increasing. How to efficiently record and translate human physical and physiological signals and generate corresponding feedback on machines and computers is a key research challenge. Compared with traditional human-computer interfaces, hydrogel-based flexible human-computer interaction devices can better conform to the skin, have strong biocompatibility, and adapt to human movement.

[0003] Flexible touchscreens and flexible sensors are important human-computer interaction input devices. Currently, research has been conducted on the sensitivity, tensile strength, bending resistance, compression resistance, and freeze resistance of flexible touchscreens and sensors. Regarding touchscreens, Chinese invention patent application CN118939142A discloses a boron nitride-based capacitive flexible touchscreen, enabling flexible use. Kim et al. prepared a simple polyacrylamide / LiCl hydrogel electrolyte that can calculate the position of human touch by applying an external AC signal, achieving touch control, and can function normally under 300% one-dimensional stretching (Kim, C.-C., Lee, H.-H., Oh, KH & Sun, J.-Y. Highly Stretchable, Transparent Ionic Touch Panel. Science 353, 682-687, 2016). Regarding flexible sensors, Chinese invention patent application CN118955953A discloses a flexible cellulose hydrogel with good tensile and self-adhesive properties, which can be used to monitor movement signals of different human joints. Chinese invention patent application CN118999631A discloses a silver nanowire-based freeze-resistant, self-powered hydrogel flexible sensor capable of self-powered sensing with strain up to 600%, still able to monitor human movement at low temperatures. Currently, the tensile strength and self-healing properties of hydrogel materials have been extensively studied, but their application in flexible touchscreens and flexible sensors remains limited. In current research, most hydrogel flexible touchscreens and sensors have an elongation at break of less than 2000% and are difficult to self-heal. Furthermore, while hydrogel flexible touchscreens can provide touch signal feedback, their functional diversity is limited, restricting their application in flexible electronic devices. Although flexible sensors can detect human movement, their sensitivity is typically around 2, significantly different from traditional sensors. Moreover, current methods for preparing hydrogel flexible touchscreens and sensors require the addition of initiators, oxidants, or reducing agents. Therefore, the preparation and application of flexible touchscreens and flexible sensors still have many shortcomings worthy of further research and improvement. Summary of the Invention

[0004] The purpose of this invention is to design a novel flexible multifunctional input device and prepare a hydrophilic polymer-hydrophobic crosslinking agent-liquid metal double crosslinked conductive hydrogel to solve the problems of insufficient tensile strength, single function and limited sensitivity of current flexible touch screens and sensors, and overcome the shortcomings of existing conductive hydrogel preparation methods that require the addition of initiators, oxidants or reducing agents.

[0005] This invention develops a conductive hydrogel with high tensile strength, high sensitivity, and simultaneous touch screen and sensor functions. First, a precursor solution is prepared using ultrasonic dispersion, and then the conductive hydrogel is prepared by polymerization and crosslinking initiated by gamma ray or electron beam irradiation.

[0006] Specifically, the flexible multifunctional input device proposed in this invention is based on a conductive hydrogel mainly composed of hydrophilic polymer chains through hydrophobic and electrostatic cross-linking nodes, with the addition of liquid metal conductive fillers to improve conductivity and responsiveness. On one hand, this invention utilizes a hydrophobic cross-linking agent to polymerize and form unique hydrophobic cross-linking nodes, enabling the hydrophilic polymer chains to elongate under stretching conditions through the depolymerization of these nodes. On the other hand, by introducing liquid metal for electrostatic physical cross-linking, the hydrogel exhibits better tensile properties and self-healing capabilities, while simultaneously improving its conductivity and responsiveness. By connecting this hydrogel to specific circuits, it can be assembled into a flexible input device with functions such as a flexible touchscreen and sensors.

[0007] The monomers used to synthesize the hydrophilic polymer chains must be water-soluble and can be acrylic acid, acrylamide, methacrylamide, methacrylic acid, vinylpyrrolidone, hydroxyethyl methacrylate, etc., with acrylic acid being preferred.

[0008] The hydrophobic crosslinking agent needs to have multiple crosslinking sites and be hydrophobic. It can be divinylbenzene, polyethylene glycol dimethacrylate, triallyl isocyanurate, octadiene, etc., with divinylbenzene being preferred.

[0009] To promote the formation of micelles by hydrophobic crosslinking agents, surfactants need to be added. These surfactants can be sodium dodecyl sulfate, sodium stearate, benzalkonium chloride, trimethylbenzyl ammonium hydroxide, polyoxyethylene dehydrated sorbitan monolaurate, etc., with sodium dodecyl sulfate being preferred.

[0010] Liquid metals enhance the conductivity of hydrogels and provide physical cross-linking nodes. They can be low-melting-point alloys with melting points of 10–30°C, such as GaIn alloys, GaSn alloys, GaNi alloys, and GaInSn alloys, which are composed of Ga and other metals in various proportions. Preferably, alloys with a Ga:In mass ratio of 3:1 are used.

[0011] The method for preparing the conductive hydrogel for flexible multifunctional input devices according to the present invention includes the following steps:

[0012] 1) Prepare a precursor solution, wherein the precursor solution is an aqueous solution containing a water-soluble polymer monomer, a surfactant, and a hydrophobic crosslinking agent;

[0013] 2) Add liquid metal to the precursor solution prepared in step 1) and sonicate it to disperse it evenly;

[0014] 3) Irradiate the solution prepared in step 2) with γ-rays or electron beams to prepare a conductive hydrogel.

[0015] In the precursor solution prepared in step 1) of the above method, the preferred concentration of the water-soluble polymer monomer is 30-300 g / L, the preferred concentration of the surfactant is 1-10 g / L, and the preferred concentration of the hydrophobic crosslinking agent is 0.1-10 g / L.

[0016] In step 2) of the above method, the preferred concentration of the liquid metal is 10 to 1000 mg / mL.

[0017] In step 3) of the above method, the absorbed dose rate of the γ-ray irradiation is preferably 1-100 Gy / min, and the absorbed dose is preferably 100-10000 Gy; the absorbed dose rate of the electron beam irradiation is preferably 5-20 kGy / pass, and the absorbed dose is preferably 100-10000 Gy.

[0018] This invention tested the tensile and application properties of the above-mentioned flexible conductive hydrogel, which provides touch control and strain sensing applications under normal and tensile conditions, and can be applied to flexible multifunctional input devices.

[0019] The flexible multifunctional input device of the present invention has the following advantages compared with currently disclosed flexible touch screens and flexible sensor materials:

[0020] 1) The flexible multifunctional input device of the present invention has significant advantages in stretchability, self-healing, functional diversity and sensitivity;

[0021] 2) The flexible multifunctional input device of the present invention has a one-dimensional tensile strainability of over 5500% and a two-dimensional tensile strainability of 7000%.

[0022] 3) The flexible multifunctional input device of the present invention can achieve self-healing within 30 minutes of cutting and bonding, and can restore 1600% of tensile strainability after full healing;

[0023] 4) The flexible multi-functional input device of the present invention can realize the basic functions of a touch screen, including drawing, button pressing and mouse control;

[0024] 5) The flexible multifunctional input device of the present invention can respond to strains such as tension, compression, and bending, and its sensitivity exceeds 10.0 at 500% strain.

[0025] 6) The flexible multi-functional input device of the present invention can switch functions under changes in external electrical signal input.

[0026] In summary, this invention employs a hydrophilic polymer-hydrophobic / electrostatic double crosslinked hydrogel synthesis strategy. The conductive hydrogel prepared by radiation synthesis can be applied to flexible multifunctional input devices, achieving a breakthrough in the stretchability of input devices. It can achieve large-scale one-dimensional and two-dimensional stretching without breakage, and can self-heal and function normally under damage. It has unique application advantages and broad application prospects in the field of flexible electronic devices. Attached Figure Description

[0027] To better illustrate the technical solution of the present invention, some aspects of the flexible multifunctional input device prepared according to the embodiments of the present invention are described in detail with accompanying drawings, but these drawings should not be construed as limiting the scope of the present invention. Those skilled in the art can obtain other related drawings based on these drawings without any creative effort.

[0028] Figure 1 A schematic diagram of the preparation method of polyacrylic acid-divinylbenzene-GaIn alloy hydrogel in Example 1.

[0029] Figure 2 Optical photographs of the polyacrylic acid-divinylbenzene-GaIn alloy hydrogel prepared in Example 1, (a), (b), and (c) show the hydrogel in its flat, folded, and twisted states, respectively.

[0030] Figure 3 The compositional characterization of the polyacrylic acid-divinylbenzene-GaIn alloy hydrogel prepared in Example 1, wherein (a) and (b) are X-ray photoelectron spectra of Ga and In, respectively, (c) is an X-ray diffraction pattern, and (d) is a Fourier transform infrared spectrum.

[0031] Figure 4 The morphology and elemental distribution of the polyacrylic acid-divinylbenzene-GaIn alloy hydrogel prepared in Example 1 are characterized, wherein (a) and (b) are scanning electron microscope images of the hydrogel, (c) is a scanning electron microscope image of the hydrogel after self-healing, and (d) is an EDS elemental distribution map of the polyacrylic acid-divinylbenzene-GaIn alloy hydrogel.

[0032] Figure 5The tensile properties of polyacrylic acid-divinylbenzene-GaIn alloy hydrogels prepared under different conditions in Examples 2 to 5 are shown in (a) for polyacrylic acid-divinylbenzene-GaIn alloy hydrogels prepared under different acrylic acid concentrations, (b) for polyacrylic acid-divinylbenzene-GaIn alloy hydrogels prepared under different irradiated absorbed doses, (c) for polyacrylic acid-divinylbenzene-GaIn alloy hydrogels prepared under different divinylbenzene concentrations, and (d) for polyacrylic acid-divinylbenzene-GaIn alloy hydrogels prepared under different GaIn alloy concentrations.

[0033] Figure 6 Tensile curve (a) and cyclic tensile curve (b) of the polyacrylic acid-divinylbenzene-GaIn alloy hydrogel prepared in Example 6.

[0034] Figure 7 Optical photographs of the polyacrylic acid-divinylbenzene-GaIn alloy hydrogel prepared in Example 7 before (a) and after (b) two-dimensional stretching.

[0035] Figure 8 Compression curve of the polyacrylic acid-divinylbenzene-GaIn alloy hydrogel prepared in Example 8.

[0036] Figure 9 Optical photographs of the polyacrylic acid-divinylbenzene-GaIn alloy hydrogel prepared in Example 9 after cutting and after self-healing.

[0037] Figure 10 The circuit diagram (a) and physical diagram (b) of the polyacrylic acid-divinylbenzene-GaIn alloy hydrogel prepared in Example 10 assembled into a one-dimensional touch screen.

[0038] Figure 11 The touch performance of the polyacrylic acid-divinylbenzene-GaIn alloy hydrogel prepared in Example 10 after being assembled into a one-dimensional touch screen is shown in (a), where (b) is the electrical signal diagram of touching different positions, (c) is the signal delay diagram after touching, (d) is the electrical signal diagram of touching different positions under stretching, and (d) is the electrical signal diagram of touching different positions after multiple self-healing.

[0039] Figure 12 The circuit diagram (a) and physical diagram (b) of the polyacrylic acid-divinylbenzene-GaIn alloy hydrogel prepared in Example 11 assembled into a two-dimensional touch screen.

[0040] Figure 13Optical photographs of the practical application of the polyacrylic acid-divinylbenzene-GaIn alloy hydrogel prepared in Example 11 assembled into a two-dimensional touch screen, including character writing (a), button control (b), and mouse control (c).

[0041] Figure 14 The sensing performance of the polyacrylic acid-divinylbenzene-GaIn alloy hydrogel assembled into a strain sensor in Example 12 includes the resistance change graphs of the polyacrylic acid-divinylbenzene-GaIn alloy hydrogel under tension (a), bending (b) and compression (c), and the resistance change graph (d) after 1000 cycles of cyclic stretching.

[0042] Figure 15 The polyacrylic acid-divinylbenzene-GaIn alloy hydrogel prepared in Example 13 was assembled into a strain sensor to record signals of various muscle and joint movements in the human body, including swallowing (a), arm bending (b), fist clenching (c), finger bending (d), leg kicking (e), and foot pedaling (f).

[0043] Figure 16 The circuit diagram and function conversion diagram of the polyacrylic acid-divinylbenzene-GaIn alloy hydrogel prepared in Example 14 assembled into a flexible multifunctional input device. Detailed Implementation

[0044] The following examples illustrate the invention in detail, but the invention is not limited thereto. Unless otherwise specified, the experimental methods described in the examples are conventional methods; the reagents and materials described are commercially available unless otherwise specified. The material testing machine used in the examples is an Instron 5969 from Instron Corporation, USA, and the signal acquisition and amplification system uses a Lingzhi Electronics DAQ-122 device.

[0045] Example 1: Preparation of polyacrylic acid-divinylbenzene-GaIn alloy hydrogel

[0046] Preparation process as follows Figure 1 As shown, the details are as follows:

[0047] 1) Prepare a mixed aqueous solution containing 280 g / L acrylic acid, 6 g / L sodium dodecyl sulfate, and 13 g / L divinylbenzene;

[0048] 2) Add 80 g / L of GaIn alloy with a Ga:In mass ratio of 3:1 to the solution obtained in step 1), and disperse it evenly by ultrasonication;

[0049] 3) The solution obtained in step 2) was irradiated with γ-rays at an absorbed dose rate of 16 Gy / min for 25 min to form a double crosslinked polyacrylic acid network with divinylbenzene as the chemical crosslinking node and GaIn alloy as the physical crosslinking node, thus obtaining polyacrylic acid-divinylbenzene-GaIn alloy hydrogel.

[0050] Figure 2 Optical photographs of the prepared polyacrylic acid-divinylbenzene-GaIn alloy hydrogel are shown, which exhibits good flexibility and can be freely bent, folded, and twisted.

[0051] Figure 3 A series of characterizations of the polyacrylic acid-divinylbenzene-GaIn alloy hydrogel revealed its composition and structure. X-ray photoelectron spectroscopy (XPS) of the polyacrylic acid-divinylbenzene-GaIn alloy hydrogel (a) and In spectrum (b) showed that it simultaneously possessed +3 and 0 valence states, indicating that the GaIn alloy, while maintaining its metallic elemental state, also acted as a physical crosslinking node within the hydrogel. (c) showed the X-ray diffraction spectra of the polyacrylic acid-divinylbenzene-GaIn alloy hydrogel, the GaIn alloy, Ga metal, and In metal. The GaIn crystal peak disappeared after alloy formation, indicating its liquid composition. (d) showed the Fourier transform infrared spectra of the polyacrylic acid-divinylbenzene-GaIn alloy hydrogel, the polyacrylic acid-divinylbenzene hydrogel, acrylic acid, and divinylbenzene. The carboxyl peak and carboxylate peak in the polyacrylic acid-divinylbenzene-GaIn alloy hydrogel had similar intensities, while in the polyacrylic acid-divinylbenzene hydrogel and the monomeric acrylic acid, the carboxyl peak intensity was significantly higher than that of the carboxylate peak, confirming the physical crosslinking effect between the GaIn alloy and the carboxylate. The disappearance of the carbon-carbon double bond peak indicates that the polymerization and cross-linking reaction is complete and the monomer conversion is complete.

[0052] Figure 4 The morphology and composition of the polyacrylic acid-divinylbenzene-GaIn alloy hydrogel are shown. (a) indicates that the hydrogel has a porous three-dimensional network structure with a pore size of approximately 5 μm; (b) shows that spherical GaIn alloy particles are uniformly distributed in the network framework and pores, with a particle size of approximately 1–3 μm; (c) shows that the hydrogel self-heals after being cut, with new gel networks forming on top of the damaged old network, confirming its self-healing properties; (d) the elemental distribution on the hydrogel surface was analyzed using energy dispersive spectroscopy (EDS). The carbon element in the gel framework is uniformly distributed, while Ga and In are concentrated in the spherical particles and are also uniformly distributed throughout the hydrogel.

[0053] Example 2: Tensile properties of polyacrylic acid-divinylbenzene-GaIn alloy hydrogels prepared under different acrylic acid concentrations

[0054] Polyacrylic acid-divinylbenzene-GaIn alloy hydrogels were prepared under the following synthesis conditions: 140–420 g / L acrylic acid, 13 g / L divinylbenzene, 6 g / L sodium dodecyl sulfate, 80 g / L GaIn alloy, and an absorbed dose of 400 Gy. Dumbbell-shaped samples with a gauge length of 6.0 mm, a width of 2.0 mm, and a thickness of 1.5 mm were cut using a dumbbell-shaped cutter. The tensile properties of the samples were then tested using a material testing machine at a tensile rate of 50 mm / min.

[0055] Figure 5 Figure (a) shows the tensile properties of polyacrylic acid-divinylbenzene-GaIn alloy hydrogels prepared under different acrylic acid concentrations. When the acrylic acid concentration is 140–420 g / L, the tensile strength of the hydrogel is 20–300 kPa and the elongation at break is 1800–5500%.

[0056] Example 3: Tensile properties of polyacrylic acid-divinylbenzene-GaIn alloy hydrogels prepared under different absorbed dosage conditions

[0057] Polyacrylic acid-divinylbenzene-GaIn alloy hydrogels were prepared under the following synthesis conditions: 280 g / L acrylic acid, 13 g / L divinylbenzene, 6 g / L sodium dodecyl sulfate, 80 g / L GaIn alloy, and an absorbed dose of 0–800 Gy. Dumbbell-shaped samples with a gauge length of 6.0 mm, a width of 2.0 mm, and a thickness of 1.5 mm were cut using a dumbbell-shaped cutter. The tensile properties of the samples were then tested using a material testing machine at a tensile rate of 50 mm / min.

[0058] Figure 5 Figure (b) shows the tensile properties of polyacrylic acid-divinylbenzene-GaIn alloy hydrogels prepared under different absorbed dose conditions. At an absorbed dose of ~800 Gy, the tensile strength of the hydrogel is 50-300 kPa and the elongation at break is 3000-5500%.

[0059] Example 4: Tensile properties of polyacrylic acid-divinylbenzene-GaIn alloy hydrogels prepared under different divinylbenzene concentrations

[0060] Polyacrylic acid-divinylbenzene-GaIn alloy hydrogels were prepared under the following synthesis conditions: 280 g / L acrylic acid, 6–26 g / L divinylbenzene, 6 g / L sodium dodecyl sulfate, 80 g / L GaIn alloy, and an absorbed dose of 400 Gy. Dumbbell-shaped samples with a gauge length of 6.0 mm, a width of 2.0 mm, and a thickness of 1.5 mm were cut using a dumbbell-shaped cutter. The tensile properties of the samples were then tested using a material testing machine at a tensile rate of 50 mm / min.

[0061] Figure 5Figure (c) shows the tensile properties of polyacrylic acid-divinylbenzene-GaIn alloy hydrogels prepared under different divinylbenzene concentrations. When the divinylbenzene concentration is 6–26 g / L, the tensile strength of the hydrogel is 70–300 kPa and the elongation at break is 3200–5500%.

[0062] Example 5: Tensile properties of polyacrylic acid-divinylbenzene-GaIn alloy hydrogels prepared under different GaIn alloy concentrations

[0063] Polyacrylic acid-divinylbenzene-GaIn alloy hydrogels were prepared under the following synthesis conditions: 280 g / L acrylic acid, 13 g / L divinylbenzene, 6 g / L sodium dodecyl sulfate, 0–240 g / L GaIn alloy, and an absorbed dose of 400 Gy. Dumbbell-shaped samples with a gauge length of 6.0 mm, a width of 2.0 mm, and a thickness of 1.5 mm were cut using a dumbbell-shaped cutter. The tensile properties of the samples were then tested using a material testing machine at a tensile rate of 50 mm / min.

[0064] Figure 5 Figure (d) shows the tensile properties of polyacrylic acid-divinylbenzene-GaIn alloy hydrogels prepared under different divinylbenzene concentrations. When the GaIn alloy concentration is 0–240 g / L, the tensile strength of the hydrogel is 40–300 kPa and the elongation at break is 2800–5500%.

[0065] Example 6: Tensile and cyclic tensile properties of polyacrylic acid-divinylbenzene-GaIn alloy hydrogel

[0066] Polyacrylate-divinylbenzene-GaIn alloy hydrogels were prepared under the following synthesis conditions: 280 g / L acrylic acid, 13 g / L divinylbenzene, 6 g / L sodium dodecyl sulfate, 80 g / L GaIn alloy, and an absorbed dose of 400 Gy. Dumbbell-shaped samples with a gauge length of 6.0 mm, a width of 2.0 mm, and a thickness of 1.5 mm were cut using a dumbbell-shaped cutter. The tensile properties of the samples were tested using a material testing machine at a tensile rate of 50 mm / min and the cyclic tensile properties at 4000%.

[0067] Figure 6 In Figure (a), the tensile curve of the prepared polyacrylic acid-divinylbenzene-GaIn alloy hydrogel is shown, which can achieve a tensile strength of 300 kPa and an elongation at break of 5500%. Figure 6 Figure (b) shows the cyclic tensile curves of the prepared polyacrylic acid-divinylbenzene-GaIn alloy hydrogel after five cycles of 4000% stretching, revealing a hysteresis curve related to its physical cross-linking. The stress did not decrease during the cyclic stretching process, indicating that large-amplitude stretching did not significantly damage the hydrogel structure, and the stretch-recovery exhibits good reversibility.

[0068] Example 7: Two-dimensional stretchability of polyacrylic acid-divinylbenzene-GaIn alloy hydrogel

[0069] Polyacrylate-divinylbenzene-GaIn alloy hydrogels were prepared under the following synthesis conditions: 280 g / L acrylic acid, 13 g / L divinylbenzene, 6 g / L sodium dodecyl sulfate, 80 g / L GaIn alloy, and an absorbed dose of 400 Gy. Circular samples with a diameter of 6.0 cm and a thickness of 1.5 mm were prepared using a circular mold, and the samples were then stretched in multiple directions to a radius greater than 50 cm.

[0070] Figure 7 The two-dimensional tensile properties of the prepared polyacrylic acid-divinylbenzene-GaIn alloy hydrogel were shown. It did not break or fracture even when the area was expanded to more than 7000% of the original size, indicating that the polyacrylic acid-divinylbenzene-GaIn alloy hydrogel has excellent two-dimensional tensile properties.

[0071] Example 8: Compression properties of polyacrylic acid-divinylbenzene-GaIn alloy hydrogel

[0072] Polyacrylate-divinylbenzene-GaIn alloy hydrogels were prepared under the following synthesis conditions: 280 g / L acrylic acid, 13 g / L divinylbenzene, 6 g / L sodium dodecyl sulfate, 80 g / L GaIn alloy, and an absorbed dose of 400 Gy. Cylindrical samples with a radius of 7 mm and a height of 8 mm were cut using a circular cutter, and the compressibility of the hydrogels was tested using a material testing machine at a compression rate of 1.0 mm / min.

[0073] Figure 8 The compression curve of the prepared polyacrylic acid-divinylbenzene-GaIn alloy hydrogel is shown. The hydrogel can be compressed to more than 98%, reaching a compressive strength of 10 MPa.

[0074] Example 9: Self-healing properties of polyacrylic acid-divinylbenzene-GaIn alloy hydrogel

[0075] Polyacrylate-divinylbenzene-GaIn alloy hydrogels were prepared under the following synthesis conditions: 280 g / L acrylic acid, 13 g / L divinylbenzene, 6 g / L sodium dodecyl sulfate, 80 g / L GaIn alloy, and an absorbent dose of 400 Gy. The hydrogels were cut into strips 6.0 cm long, 1.0 cm wide, and 1.5 mm thick, cut in the middle, and then bonded together. Figure 9 The study demonstrated that the hydrogel showed significant healing after 30 minutes of application.

[0076] Example 10: Polyacrylic acid-divinylbenzene-GaIn alloy hydrogel used as a one-dimensional touch screen

[0077] Polyacrylate-divinylbenzene-GaIn alloy hydrogels were prepared under the following synthesis conditions: 280 g / L acrylic acid, 13 g / L divinylbenzene, 6 g / L sodium dodecyl sulfate, 80 g / L GaIn alloy, and an absorbent dosage of 400 Gy. The hydrogels were cut into strips 6.0 cm long, 1.0 cm wide, and 1.5 mm thick. Figure 10 The circuit connection is shown in Figure (a). Electrodes are connected to both ends of the strip hydrogel. A current / voltage signal amplifier is connected in series and then connected to the positive terminal of a sinusoidal AC power supply. A signal acquisition card is used to collect and record the generated electrical signals. The negative terminal of the power supply is grounded. The actual device is shown in Figure (a). Figure 11 As shown in (b).

[0078] Figure 11 Figure (a) shows the changes in electrical signals when the touch is applied to different locations on the hydrogel one-dimensional touchscreen. V1 and V2 represent the magnitudes of the electrical signals generated at the two ends, respectively. When the hand touches from left to right, the signal strength increases on one side and decreases on the other side. Figure 11 (b) shows that the delay in signal generation is no more than 30ms. Figure 11 Figure (c) shows the intensity changes of electrical signals at different locations on the one-dimensional touchscreen with hydrogel under 500% and 1000% stretching, indicating that the touchscreen can still function normally under stretching. Figure 11 Figure (d) shows that after 1 to 5 self-healing cycles, the intensity trend of the electrical signal at the same touch location did not change significantly, indicating that it has good working stability.

[0079] Example 11: Polyacrylic acid-divinylbenzene-GaIn alloy hydrogel used as a two-dimensional touch screen

[0080] Polyacrylate-divinylbenzene-GaIn alloy hydrogels were prepared under the following synthesis conditions: 280 g / L acrylic acid, 13 g / L divinylbenzene, 6 g / L sodium dodecyl sulfate, 80 g / L GaIn alloy, and an absorbent dosage of 400 Gy. The hydrogels were cut into squares with a length and width of 6.0 cm and a thickness of 1.5 mm. Figure 12 The circuit connection is shown in Figure (a). Electrodes are connected to the four corners of the square hydrogel. After connecting the current / voltage signal amplifier in series, it is connected to the positive terminal of a sinusoidal AC power supply. The generated electrical signal is collected and recorded using a signal acquisition card. The negative terminal of the power supply is grounded. The actual device is as shown. Figure 12 As shown in (b).

[0081] Figure 13 Image (a) demonstrates the use of a two-dimensional touchscreen device to enable handwriting of the letters "PKU". Figure 13 Figure (b) demonstrates the implementation of hand-touched numeric keypad response using a two-dimensional touchscreen device. Figure 13(c) illustrates the use of a two-dimensional touchscreen device to implement hand-touch mouse control for game operation.

[0082] Example 12: Sensing signal of polyacrylic acid-divinylbenzene-GaIn alloy hydrogel under strain

[0083] Polyacrylate-divinylbenzene-GaIn alloy hydrogels were prepared under the following synthesis conditions: 280 g / L acrylic acid, 13 g / L divinylbenzene, 6 g / L sodium dodecyl sulfate, 80 g / L GaIn alloy, and an absorbed dose of 400 Gy. The hydrogels were cut into strips 3.0 cm long, 1.0 cm wide, and 1.5 mm thick. Both ends of the strips were connected to a 0.1 V DC power supply. The generated electrical signals were acquired using a data acquisition card, assembled into a strain sensor, and the current flowing through the sensor was measured and the resistance calculated.

[0084] Figure 14 (a) shows the resistance change of the device under tension, (b) shows the resistance change of the device under bending, (c) shows the resistance change of the device under compression, and (d) shows the resistance change of the device after 1000 cycles of tension.

[0085] Example 13: Polyacrylic acid-divinylbenzene-GaIn alloy hydrogel used as a human motion sensor

[0086] Polyacrylate-divinylbenzene-GaIn alloy hydrogels were prepared under the following synthesis conditions: 280 g / L acrylic acid, 13 g / L divinylbenzene, 6 g / L sodium dodecyl sulfate, 80 g / L GaIn alloy, and an absorbed dose of 400 Gy. The hydrogels were cut into strips 3.0 cm long, 1.0 cm wide, and 1.5 mm thick. Both ends of the strips were connected to a 0.1 V DC power supply. The generated electrical signals were acquired using a data acquisition card, assembled into a strain sensor, and the current flowing through the sensor was measured and the resistance calculated.

[0087] Figure 15 The results of sensing the movements of multiple joints and muscles in the human body using the device are shown. (a) swallowing, (b) arm bending, (c) fist clenching, (d) finger bending, (e) kicking, and (f) foot pedaling.

[0088] Example 14: Polyacrylic acid-divinylbenzene-GaIn alloy hydrogel used as a flexible multifunctional input device

[0089] Polyacrylate-divinylbenzene-GaIn alloy hydrogels were prepared under the following synthesis conditions: 280 g / L acrylic acid, 13 g / L divinylbenzene, 6 g / L sodium dodecyl sulfate, 80 g / L GaIn alloy, and an absorbent dosage of 400 Gy. The hydrogels were cut into squares with a length and width of 6.0 cm and a thickness of 1.5 mm. Figure 16 The circuit connection is shown below. The four corners of the square hydrogel are connected to electrodes, and a current / voltage signal amplifier is connected in series before connecting it to the power supply. When using the touch screen function, the power supply inputs the same AC sine wave signal; when using the sensing function, the power supply inputs a DC signal with a higher potential to the two electrodes on one side, and a DC signal with a lower potential to the two electrodes on the other side.

[0090] Figure 16 This demonstrates the function switching process of a polyacrylic acid-divinylbenzene-GaIn alloy hydrogel used as a flexible multifunctional input device: when connected to an external AC signal, it can function as a touchscreen to perform operations such as music switching and volume adjustment; when connected to an external DC signal, it can function as a motion sensor to record motion signals. Functional switching of the same device can be achieved by adjusting the external electrical signal without changing the circuit connections.

[0091] Example 15: Tensile properties, self-healing properties, touchscreen properties, strain sensing properties, and functional conversion properties of polyacrylic acid-divinylbenzene-GaIn alloy hydrogel synthesized by electron beam irradiation.

[0092] Polyacrylate-divinylbenzene-GaIn alloy hydrogels synthesized using electron accelerators under electron beam irradiation conditions of 1–10 kGy / pass dose rates and 0.1–10 kGy doses exhibit tensile properties, self-healing properties, touchscreen properties, strain sensing properties, and functional conversion properties that are almost identical to those synthesized using gamma-ray radiation methods.

[0093] Example 16: Tensile properties, self-healing properties, touchscreen properties, strain sensing properties, and functional conversion properties of polyacrylamide-divinylbenzene-GaIn alloy hydrogels synthesized by gamma ray or electron beam irradiation.

[0094] Polyacrylamide-divinylbenzene-GaIn alloy hydrogels synthesized by gamma ray or electron beam irradiation exhibit almost identical tensile properties, self-healing properties, touchscreen properties, strain sensing properties, and functional conversion properties to polyacrylic acid-divinylbenzene-GaIn alloy hydrogels.

[0095] Example 17: Tensile properties, self-healing properties, touchscreen properties, strain sensing properties, and functional conversion properties of polyacrylic acid-polyethylene glycol dimethacrylate-GaIn alloy hydrogels synthesized by gamma ray or electron beam irradiation.

[0096] Polyacrylic acid-polyethylene glycol dimethacrylate-GaIn alloy hydrogels synthesized by gamma ray or electron beam irradiation exhibit almost the same tensile properties, self-healing properties, touch screen properties, strain sensing properties, and functional conversion properties as polyacrylic acid-divinylbenzene-GaIn alloy hydrogels.

[0097] Example 18: Tensile properties, self-healing properties, touchscreen properties, strain sensing properties, and functional conversion properties of polyacrylic acid-divinylbenzene-GaSn alloy hydrogels synthesized by gamma ray or electron beam irradiation.

[0098] Polyacrylate-divinylbenzene-GaSn alloy hydrogels synthesized by gamma ray or electron beam irradiation exhibit almost identical tensile properties, self-healing properties, touchscreen properties, strain sensing properties, and functional conversion properties to polyacrylate-divinylbenzene-GaIn alloy hydrogels.

Claims

1. An electrically conductive hydrogel consisting essentially of hydrophilic polymer chains through hydrophobic cross-linking nodes and electrostatic cross-linking nodes, characterized in that, The hydrogel is added with liquid metal as conductive filler, wherein the hydrophobic cross-linking nodes between the hydrophilic polymer chains are formed by hydrophobic cross-linking agent, and the electrostatic cross-linking nodes between the hydrophilic polymer chains are provided by liquid metal.

2. The conductive hydrogel of claim 1, wherein, The hydrophilic polymer chains are obtained by polymerization of water-soluble polymer monomers selected from one or more of the following monomers: acrylic acid, methacrylic acid, hydroxyethyl methacrylate.

3. The conductive hydrogel of claim 1, wherein, The hydrophobic cross-linking agent is selected from one or more of the following compounds: divinylbenzene, polyethylene glycol dimethacrylate, triallyl isocyanurate, octadiene.

4. The conductive hydrogel of claim 1, wherein, The liquid metal is a low-melting-point alloy composed of Ga and other metals.

5. The conductive hydrogel of claim 4, wherein, The low-melting-point alloy is selected from GaIn alloy, GaSn alloy, GaNi alloy, GaInSn alloy.

6. The conductive hydrogel of claim 4, wherein, The liquid metal is an alloy with Ga:In mass ratio of 3:

1.

7. The conductive hydrogel of claim 1, wherein, The conductive hydrogel is prepared by adding liquid metal into an aqueous solution containing water-soluble polymer monomers, surfactants and hydrophobic cross-linking agents, ultrasonic dispersion, and then initiating polymerization and cross-linking by γ-ray or electron beam irradiation.

8. The preparation method of the conductive hydrogel according to any one of claims 1-7, comprising the following steps: 1) preparing a precursor solution, which is an aqueous solution containing water-soluble polymer monomers, surfactants and hydrophobic cross-linking agents; 2) adding liquid metal into the precursor solution prepared in step 1) and ultrasonic dispersion to make it uniformly dispersed; 3) preparing the conductive hydrogel by γ-ray or electron beam irradiation of the solution prepared in step 2).

9. The production method according to claim 8, wherein The surfactant in step 1) is selected from one or more of the following compounds: sodium dodecyl sulfate, sodium stearate, benzalkonium chloride, trimethylbenzylammonium hydroxide, polyoxyethylene sorbitan monolaurate.

10. The production method according to claim 8, wherein In the precursor solution prepared in step 1), the concentration of water-soluble polymer monomers is 30-300 g / L, the concentration of surfactants is 1-10 g / L, and the concentration of hydrophobic cross-linking agents is 0.1-10 g / L; in the solution obtained in step 2), the concentration of liquid metal is 10-1000 mg / mL.

11. The production method according to claim 8, wherein In step 3), γ-ray irradiation is used with an absorbed dose rate of 1-100 Gy / min and an absorbed dose of 100-10000 Gy; or electron beam irradiation is used with an absorbed dose rate of 5-20 kGy / pass and an absorbed dose of 100-10000 Gy.

12. The conductive hydrogel according to any one of claims 1-7 for use in a flexible input device.

13. A flexible input device, comprising: The flexible input device comprises the conductive hydrogel according to any one of claims 1-7 and a circuit connected thereto.

14. The flexible input device of claim 13, wherein, The flexible input device is a touch screen or a sensor.

15. The flexible input device of claim 13, wherein, The flexible input device is a flexible multifunctional input device, which realizes touch screen and sensor function switching by changing external input electric signals.

Images