Research On Surface Microstructure Design And Sensing Mechanism Of Flexible Mxene Film

With the advent of the intelligent age,people’s demand for flexible and soft electronic devices is increasing.Intelligent sensors with excellent sensing performance and satisfying mechanical performance have always been the focus of attention by suitable material selection and exquisite structure design.In this paper,MXene(Ti3C2Tx),an emerging two-dimensional material with excellent conductivity and abundant surface-active groups,was obtained by wet chemical method firstly.Then,two kinds of MXene film-based pressure sensors with different microstructures were designed and fabricated by the substrate shrinkage method which is simple and easy-to-use.It was investigated that the impact of material properties and sheets structure on sensing performance,when pristine MXene film had been assembled to the flexible pressure sensor.It also focuses on the gain effects of films’ surface microstructure design on sensing performance.The sensing mechanism was further analyzed,and its application prospect was predicted according to the sensing characteristics of the sensor.The specific contents are as follows:(1)MXene dispersion was prepared by the wet chemical method.The etching degree of MXene obtained was relatively complete,and the existence of Al element from its parent phase(Ti3AlC2)was not detected.The MXene single sheet can meet micron-sized.The MXene self-supporting film was obtained by vacuum pumping and filtration.The obtained self-supporting film has a certain degree of flexibility,and its cross-section images show the structure of sheets inter-stack.By exploring the experimental parameters in the preparation process of MXene,it can be seen that the sheets size and yield of the product could be controlled by different stratification methods.Therefore,the parameters can be adjusted to get the MXene products suitable for the target requirements.(2)Based on the MXene dispersion obtained earlier,the MXene flexible film with continuous wrinkled structure was designed and prepared by the method of uniaxial pre-stretching and shrinkage of substrate.By applying the pleated MXene film to the flexible sensors,it can be evaluated that the assembled sensor shows extremely high sensitivity(593.25 kPa-1)with slight pressure and a wide detect range(0.49 Pa-29.4 kPa).Under the continuous pressure,the sensor can output relatively stable electrical signals,showing cycling stability.The sensor can measure the pressure of as little as one grain of millet(2.4 mg).The response and recovery time is 40/53 ms under the small pressure.According to the sensitivity characteristic curve and mechanical principle of the sensor,the sensing mechanism of the pleated MXene film-based pressure sensor is further discussed.A simple mechanical model is established for the analysis and demonstration of sensing mechanism.Furthermore,combining with the sensing characteristics,the precise recognition and quality testing of small objects by the sensor are realized.And it is explored that the sensor could be applied in the testing of human physiological signals.(3)A MXene film-based flexible pressure sensor with kink structure was designed and fabricated by a two-mode shrinkage method of stress shrinkage combined with temperature shrinkage.Under continuous pressure,this pressure sensor can output more stable electrical signals than the pleated MXene filmbased sensor.And it has more excellent cycle stability.According to the comparison,the comprehensive performance of the sensor obtained from the flexible film assembled with 100%pre-stretching ratio is the best.The working sensitivity of the sensor is 64.56 kPa-1,the sensing range is 4.9 Pa-98 kPa.The sensor can also recognize the small objects and output stable electrical signals.The response and recovery time is 59/15 ms under the small pressure.Considering that the sensor has more stable circulating electrical signals(18000 cycles),the influence of different membrane surface microstructure design on the sensing characteristics of the sensor is discussed compared with the previous chapter.According to the sensitivity characteristic curve,and combined with the analysis of the sensing mechanism of the pleated MXene film-based sensor in the previous chapter,the sensing mechanism of the kink MXene film-based sensor is explained by establishing a model.Further combined with the sensing characteristics of the sensor to realize the recognition of human facial emotions,it can be explored that the sensor has the potential in the field of humancomputer interaction and robotics.