CN111561971A - A multifunctional electronic skin based on conductive cellulose liquid crystal hydrogel - Google Patents

Abstract

The invention relates to a multifunctional electronic skin based on a conductive cellulose liquid crystal hydrogel, comprising a conductive cellulose liquid crystal hydrogel, a wire and a flexible transparent protective film; the conductive cellulose liquid crystal hydrogel is encapsulated in the flexible transparent protective film , with wires inserted at both ends. The multifunctional electronic skin based on the conductive cellulose liquid crystal hydrogel of the present invention can respond to external stimuli such as temperature, pressure, tension and torsion, and convert them into electrical signals and visualized optical signals. The multifunctional electronic skin based on the conductive cellulose liquid crystal hydrogel of the present invention can not only quantitatively output stimulation through electrical signals, but also position the stimulation through visual optical signals, and has the advantages of wear resistance, low cost, and reusability. , multi-function, convenient and reliable, etc., can be used in the field of visual user interface.

Description

A multifunctional electronic skin based on conductive cellulose liquid crystal hydrogel

technical field

The invention relates to the field of biological materials, in particular to a multifunctional electronic skin based on conductive cellulose liquid crystal hydrogel.

Background technique

The skin is the physical barrier between the human body and the external environment, converting external stimuli such as temperature, pressure, tension and twisting forces into electrical signals that the brain receives to generate safe and effective instructions. Due to its high applicability in fields such as artificial prostheses, smart robots, wearable devices, and medical diagnostics, this multisensory function has motivated researchers to develop artificial flexible electronic skins with similar responsiveness. By incorporating different conductive agents, such as metals, alloys, liquid metals, ions, semiconductors, and carbon nanomaterials, many electronic skins have been developed that can feedback external stimuli. Among the above conductive agents, carbon nanotubes (CNTs) are widely used due to their excellent electrical conductivity, heat permeability and mechanical properties. However, most flexible electronic skins with integrated carbon nanotubes lack the function of visualizing data, so electronic instruments need to be connected externally to process and display electrical signals. Furthermore, the single electrical signal output of these devices is difficult to locate the stimulation site and prone to causing errors under interference. The above-mentioned defects greatly limit the application scope of electronic skins containing carbon nanotubes.

To endow the electronic skin with the characteristics of data visualization, smart structural color hydrogels can be used as scaffold materials. The material has periodic nanostructures that can tune the light propagation path. Among them, intelligent responsive polymers can provide materials with responsiveness to external stimuli. In particular, when cellulose liquid crystals were combined with smart hydrogel scaffolds, the resulting composite hydrogels could generate structural colors at specific cellulose concentrations, and these colors also changed with the internal nanostructures under external stimuli changes due to changes. In addition, as the most abundant natural polymer in nature, cellulose has low cost, good biodegradability and biocompatibility, and has great research value.

Therefore, in the present invention, we use the smart cellulose liquid crystal hydrogel as the main material of the electronic skin doped with carbon nanotubes, and design and invent a kind of electronic skin that can respond to various external stimuli and can convert the stimuli signal. Visualized new electronic skin can be used in fields such as health care and biosensing.

SUMMARY OF THE INVENTION

In order to solve the shortcoming that the current electronic skin cannot visualize the stimulation signal and locate the stimulation site, the present invention provides a multifunctional electronic skin based on a conductive cellulose liquid crystal hydrogel.

For achieving the above object, the technical scheme provided by the present invention is:

A multifunctional electronic skin based on a conductive cellulose liquid crystal hydrogel, comprising a conductive cellulose liquid crystal hydrogel, a wire and a flexible transparent protective film; the conductive cellulose liquid crystal hydrogel is encapsulated in the flexible transparent protective film, and is Wires are inserted at both ends.

Its preparation method comprises the following steps:

(1) preparing the precursor solution of conductive cellulose liquid crystal hydrogel;

(2) Pour the prepolymer solution of the conductive cellulose liquid crystal hydrogel into the mold, and conduct photopolymerization by ultraviolet light; take the polymerized hydrogel out of the mold, and then insert two wires at both ends of the hydrogel. The hydrogel was encapsulated with a flexible transparent protective film.

The prepolymer solution of the conductive cellulose liquid crystal hydrogel described in step (1) is formed by mixing hydroxypropyl cellulose nanocrystals, carbon nanotubes and the prepolymer solution of the smart hydrogel; The mass fraction of cellulose nanocrystals is 50%-70%, and the mass fraction of carbon nanotubes is 0.15%-5%.

The prepolymer solution of the smart hydrogel described in step (1) is selected from one or more of acrylic acid, acrylamide, isopropylacrylamide and methacrylate gelatin.

If the prepolymer solution of the conductive cellulose liquid crystal hydrogel described in step (1) needs to be stored after being configured, it should be stored at an ambient temperature of 4°C in the dark, and stirred evenly once a week for 24 hours each time.

The flexible transparent protective film described in step (2) is made of polydimethylsiloxane PDMS.

The thickness of the flexible transparent protective film described in step (2) is 50-100 nm.

The thickness of the hydrogel after polymerization in step (2) is 100-500 nm.

Compared with the prior art, the beneficial effects of the present invention are:

1) The conductive cellulose liquid crystal hydrogel prepared by the present invention has the characteristic of optically responding to external stimuli such as temperature, pressure, tension and torsion force, and its versatility makes it applicable to various practical scenarios.

2) The multifunctional electronic skin based on the conductive cellulose liquid crystal hydrogel of the present invention can not only quantitatively output the stimulation through electrical signals, but also locate the stimulation through visual optical signals, and has the advantages of wear resistance, low cost, and flexibility. Reusable, multi-functional, convenient and reliable. It can be applied to the field of visual user interaction interface. In addition to the output of electrical signals, it can also convert external stimuli into visual optical signals, so as to realize the localization of the stimulation site.

3) The stimulation response of the multifunctional electronic skin based on the conductive cellulose liquid crystal hydrogel of the present invention is reversible, and can be restored to the original state after the stimulation ends, and the outer layer is wrapped with a flexible protective film, which is not easy to damage and can be repeated use many times.

Description of drawings

Figure 1 is a cross-sectional view of a multifunctional electronic skin based on conductive cellulose liquid crystal hydrogels.

Figure 2 is a top view of a multifunctional electronic skin based on conductive cellulose liquid crystal hydrogels.

Figure 3 is a schematic diagram of the structure of the conductive cellulose liquid crystal hydrogel.

FIG. 4 is a scanning electron microscope picture of a cross section of a conductive cellulose liquid crystal hydrogel.

Figure 5 is a graph of the real-time change of resistance of the multifunctional electronic skin based on conductive cellulose liquid crystal hydrogel for real-time temperature sensing experiments.

Figure 6 is a graph of the real-time change in resistance of a multifunctional electronic skin based on conductive cellulose liquid crystal hydrogel for real-time pressure sensing experiments.

The parts in the drawings are marked as follows: 1- flexible transparent protective film, 2- conductive cellulose liquid crystal hydrogel, 3- cellulose liquid crystal, 4- wire.

Detailed ways

The present invention will be described in further detail below with reference to specific embodiments. The following examples are only used to illustrate the present invention and not to limit the scope of the present invention.

The above scheme will be further described below in conjunction with specific embodiments. It should be understood that these examples are intended to illustrate the invention and not to limit the scope of the invention. All equivalent transformations or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention. The implementation conditions not specified in the examples are usually the conditions in routine experiments.

Example 1 Multifunctional electronic skin based on conductive cellulose liquid crystal hydrogel

(1) Preparation steps of the precursor solution of the conductive cellulose liquid crystal hydrogel:

The mass fraction of 5% acrylamide (AAm, polymer monomer), 5% of acrylic acid (AAc, polymer monomer) mass fraction of 0.3% N,N'-methylenebisacrylamide (Bis, cross-linking agent), 0.1% α-hydroxyisobutyryl benzene (HMPP, photoinitiator) and deionized water were mixed to obtain the precursor solution of polyacrylamide hydrogel; % hydroxypropyl cellulose, carbon nanotubes with a mass fraction of 2% are mixed with the prepolymer solution of polyacrylamide hydrogel to obtain the prepolymer solution of conductive cellulose liquid crystal hydrogel; during the stirring process, The stirrer continued to work continuously, adding 50 mg of cellulose nanocrystals every 30 minutes to ensure that it was evenly dispersed in the solution; after all the powders were evenly mixed, the stirrer continued to stir for more than a week; before the obtained conductive cellulose liquid crystal hydrogel If the polymer solution needs to be stored after configuration, it should be stored at an ambient temperature of 4 °C in the dark, and stirred evenly once a week for 24 hours each time.

(2) Preparation steps of multifunctional electronic skin based on conductive cellulose liquid crystal hydrogel:

Pour the prepolymer solution of the conductive cellulose liquid crystal hydrogel into a mold with a size of 500mm*400mm*5mm (length*width*height), and photopolymerize it with ultraviolet light. The polymerization time is 1min. The hydrogel was taken out from the mold, and then two wires with a length of 200 mm were inserted at both ends, and the hydrogel was encapsulated with a flexible transparent protective film, and finally an electronic skin with a visual user interface was obtained.

Example 2 Multifunctional electronic skin based on conductive cellulose liquid crystal hydrogel for real-time sensing

(1) Multifunctional electronic skin based on conductive cellulose liquid crystal hydrogel for real-time temperature sensing

The multifunctional electronic skin based on conductive cellulose liquid crystal hydrogel prepared in Example 1 was attached to the arm, the wires at both ends were connected to the two poles of the multimeter, and the resistance of the electronic skin was measured with the multimeter. Touch the electronic skin repeatedly with an ice cube with a size of 100mm*100mm*100mm for about 5 seconds each time, then remove it and wait for about 25 seconds. During this period, the color change of the electronic skin was observed, and a multimeter was used to record the real-time change of the electronic skin resistance. It was observed that each time the ice cube touched the electronic skin, the color of the material at the touch location changed, and the color gradually recovered after the ice cube was removed. And the resistance of the electronic skin will also change in real time, and the change range is related to the real-time temperature, as shown in Figure 5. It can be seen that the prepared electronic skin can respond to temperature in real time, locate the stimulation site through color, and reflect the real-time temperature change of the material through real-time resistance change. The experimental results demonstrate that the multifunctional electronic skin based on conductive cellulose liquid crystal hydrogel has a good application function in real-time temperature sensing.

(2) Multifunctional electronic skin based on conductive cellulose liquid crystal hydrogel for real-time pressure sensing

The multifunctional electronic skin based on conductive cellulose liquid crystal hydrogel prepared in Example 1 was attached to the arm, the wires at both ends were connected to the two poles of the multimeter, and the resistance of the electronic skin was measured by the multimeter. Press the electronic skin with your finger at a pressure of about 20kPa for about 3 seconds each time, then remove it and wait for about 15 seconds. During this period, the color change of the electronic skin was observed, and a multimeter was used to record the real-time change of the electronic skin resistance. It was observed that each time the finger pressed the electronic skin, the color of the material at the touch location changed, and the color gradually recovered when the finger was removed. And the resistance of the electronic skin will also change in real time, and the change range is related to the real-time pressure, as shown in Figure 5. It can be seen that the prepared electronic skin can respond to the pressure in real time, locate the stimulation site by color, and reflect the real-time pressure change of the material through the real-time resistance change. The experimental results demonstrate that the multifunctional electronic skin based on conductive cellulose liquid crystal hydrogel has good application function in real-time pressure sensing.

The above are only preferred embodiments of the present invention, and do not limit the present invention in any form. Any person skilled in the art, without departing from the scope of the technical solution of the present invention, according to the technical essence of the present invention, Any simple modifications, equivalent replacements and improvements made in the above embodiments still fall within the protection scope of the technical solutions of the present invention.

Claims (8)

1. a kind of multifunctional electronic skin based on conductive cellulose liquid crystal hydrogel, is characterized in that: comprise conductive cellulose liquid crystal hydrogel, wire and flexible transparent protective film; Described conductive cellulose liquid crystal hydrogel is encapsulated in flexible transparent protective film with wires inserted at both ends. 2. The multifunctional electronic skin based on conductive cellulose liquid crystal hydrogel according to claim 1, wherein the preparation method comprises the following steps: (1) preparing the precursor solution of conductive cellulose liquid crystal hydrogel; (2) Pour the prepolymer solution of the conductive cellulose liquid crystal hydrogel into the mold, and conduct photopolymerization by ultraviolet light; take the polymerized hydrogel out of the mold, and then insert two wires at both ends of the hydrogel. The hydrogel was encapsulated with a flexible transparent protective film. 3. The multifunctional electronic skin based on conductive cellulose liquid crystal hydrogel according to claim 2, characterized in that: the prepolymer solution of the conductive cellulose liquid crystal hydrogel described in step (1) is composed of hydroxypropyl Cellulose nanocrystals, carbon nanotubes and the prepolymer solution of smart hydrogel are mixed; wherein, the mass fraction of hydroxypropyl cellulose nanocrystals is 50%-70%, and the mass fraction of carbon nanotubes is 0.15% -5%. 4 . The multifunctional electronic skin based on conductive cellulose liquid crystal hydrogel according to claim 3 , wherein the precursor solution of the smart hydrogel is selected from the group consisting of acrylic acid, acrylamide, and isopropylacrylamide. 5 . and one or more of methacrylate gelatin. 5. The multifunctional electronic skin based on conductive cellulose liquid crystal hydrogel according to claim 1, characterized in that: after the prepolymer solution of the conductive cellulose liquid crystal hydrogel described in step (1) is configured, if necessary For storage, it should be stored at an ambient temperature of 4°C in the dark, and stirred evenly once a week for 24 hours each time. 6 . The multifunctional electronic skin based on conductive cellulose liquid crystal hydrogel according to claim 1 , wherein the material of the flexible transparent protective film in step (2) is polydimethylsiloxane PDMS. 7 . 7 . The multifunctional electronic skin based on conductive cellulose liquid crystal hydrogel according to claim 1 , wherein the thickness of the flexible transparent protective film in step (2) is 50-100 nm. 8 . 8 . The multifunctional electronic skin based on conductive cellulose liquid crystal hydrogel according to claim 1 , wherein the thickness of the hydrogel after polymerization in step (2) is 100-500 nm. 9 .

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