| Stimulus-responsive actuators have great potential for applications in soft robotics,artificial muscles,sensors,etc.due to their ability to change their shape in response to external stimuli.Moisture responsive actuators are limited in their responsiveness and mechanical properties due to the stiffness of the material and the limited specific surface area and weak interlayer interfacial forces due to dense stacking of the material.In this thesis,MXene nanosheets and MXene（3D-MXene）with a three-dimensional folded structure formed by spray freeze-drying were used as the base unit to construct a humidity-responsive actuator with a MXene/3D-MXene bilayer structure through vacuum-assisted filtration,which can quickly respond to changes in environmental humidity.In addition,a programmable humidity-responsive actuator was developed based on GO nanomaterials combined with aerosol jet printing technology.A programmable humidity-responsive actuator that can achieve the desired deformation effect.The specific work is as follows:（1）MXene and 3D folded MXene dispersions were deposited on a cellulose filter membrane by vacuum-assisted filtration,dried at room temperature and then uncovered to produce a two-layer homogeneous humidity-responsive actuator.The same material has better bonding between the two layers due to the van der Waals forces between the nanosheets.The introduction of this structure increases the specific surface area of the device and enhances its ability to absorb moisture while ensuring improved mechanical properties,making the MXene/3D-MXene actuator sensitive to changes in humidity.During the exploration of the optimum thickness of the film,it was found that the film corresponding to 40 mg could reach a maximum bending angle of 171°at a 65%humidity gradient and a bending speed greater than 34°s-1 in 2 s,with a high cycling stability.Comparing the humidity response tests of the MXene,3D-MXene and MXene/3D-MXene films,the MXene/3D-MXene film has the best humidity response performance and is able to cycle over gauze that is permeable to water vapour quickly.Finally,a bionic flower prepared from the actuator simulates the closing and opening of a flower;combined with MXene’s excellent electrical conductivity,a humidity-actuated smart switch was designed that can control the on/off of the circuit.（2）After aerosol jet printing,the GO nanosheets changed from a flat two-dimensional layer structure to a three-dimensional structure under the action of capillary forces during deposition and drying,and during the stacking process there was a larger gap between the nanosheet layers compared to the filtered part,which made the film in the printed area less rigid and more inclined to bend along the area in response to humidity,achieving control of the bending direction of the film to achieve the purpose of programmability.The film prepared from 19 mg GO nanosheets had the maximum bending angle,and by adjusting the number of layers of GO ink printed on the film,the30-layer GO film had the maximum bending angle and better response performance compared to the unprinted film.In addition,the bending direction of the film is influenced by the print angle,which is perpendicular to the print direction,and the integration of each print angle on the strip film allows for complex deformations.Finally,an aerosol jet print pattern on GO film was designed to create a four-leaf clover with leaves that open and shrink when stimulated by humidity and to simulate the“shy”behaviour of a mimosa grass with curled leaves. |
