▎ 摘　　要

NOVELTY - Triple stimulus responsive double-layer hydrogel actuator comprises e.g. two layers of hydrogel. The first layer of hydrogel is composed of polyacrylic acid, polyacrylamide, graphene oxide nanoribbons, dispersant. The polymerization is initiated by a lignin-potassium persulfate-metal ion initiation system. The second layer of hydrogel is composed of poly-N-isopropylacrylamide, carboxymethyl cellulose, and the polymerization is initiated using a photo-initiated method. The two-layer hydrogel exhibits good mechanical properties based on the incorporation of graphene oxide nanoribbons and the construction of a double network structure. The first layer of hydrogel also exhibits good strain sensing properties and self-healing properties. The poly N-isopropylacrylamide molecular chain contains hydrophobic isopropyl group and hydrophilic amide group, which has excellent temperature response ability. USE - The hydrogel actuator is useful in soft robot, drug delivery, smart sensing, biological medicine, tissue engineering, drug controlled release, separation extraction, sensor and bionic field. ADVANTAGE - The poly-N-isopropylacrylamide carboxymethylcellulose layer adopts photo-initiated polymerization; and provide temperature-responsive and pH-responsive capabilities for the bilayer hydrogel. The hydrogel actuator exhibits triple stimulus response properties of temperature, pH, and near-infrared light, and has potential applications in soft robotics and valve switching, improved mechanical property, self-healing ability, conductive performance, and photo-thermal conversion ability, and can realize a large angle of almost 360℃. DETAILED DESCRIPTION - Triple stimulus responsive double-layer hydrogel actuator comprises two layers of hydrogel. The first layer of hydrogel is composed of polyacrylic acid, polyacrylamide, graphene oxide nanoribbons, dispersant. The polymerization is initiated by a lignin-potassium persulfate-metal ion initiation system. The second layer of hydrogel is composed of poly-N-isopropylacrylamide, carboxymethyl cellulose, and the polymerization is initiated using a photo-initiated method. The two-layer hydrogel exhibits good mechanical properties based on the incorporation of graphene oxide nanoribbons and the construction of a double network structure. The first layer of hydrogel also exhibits good strain sensing properties and self-healing properties. The poly N-isopropylacrylamide molecular chain contains hydrophobic isopropyl group and hydrophilic amide group, which has excellent temperature response ability. The graphene oxide nanoribbons provide photothermal conversion capabilities for bilayer hydrogel actuators, and their combination with poly-N-isopropylacrylamide enables bilayer hydrogel actuators to respond to near-infrared light. The both carboxymethyl cellulose and polyacrylic acid contain carboxy groups and thus are able to respond to changes in pH to impart pH responsiveness to bilayer hydrogels. An INDEPENDENT CLAIM is included for a method for preparing triple stimulus responsive double-layer hydrogel actuator comprising (1) dispersing a certain mass of multi-walled carbon nanotubes in concentrated sulfuric acid, slowly adding potassium permanganate to it, stirring evenly under magnetic stirring, and raising the system to a certain temperature to continue stirring, adding ice water containing hydrogen peroxide to complete the reaction, allowing to stand, separating the product, and then sequentially washing many times with deionized water, hydrochloric acid solution, ethanol and diethyl ether to obtain graphene oxide nanobelts, (2) adding different amounts of two monomers, acrylic acid and acrylamide, dispersant, pre-initiation system and graphene oxide nanoribbons into a beaker and add water, stirring uniformly, adding metal ion solution under the condition of ice-water bath, stirring vigorously in a short time and pour into the mold for polymerization, and controlling the thickness of this layer of hydrogel, (3) placing N-isopropylacrylamide, cross-linking agent, graphene oxide nanoribbons, and carboxymethyl cellulose in deionized water, stirring, and adding photoinitiator and stirring for a certain period of time in an ice-water bath, pouring the obtained pregel solution on the polyacrylic acid-polyacrylamide layer, allowing to stand for a period of time, carrying out photo-initiated polymerization under an ultraviolet lamp to obtain a double-layer hydrogel, (4) cutting the bilayer hydrogel was cut into strips, and bending the strip hydrogel toward the poly-N-isopropylacrylamide-containing layer under the irradiation of near-infrared light or in hot water environment, placing the curved strip-shaped hydrogel in an acidic solution, and bending the bilayer hydrogel toward the polyacrylic acid-containing layer.