Fabrication And Performance Research Of Flexible Pressure Sensor Based On MXene

In recent years,flexible pressure sensors have attracted more and more attention,which can convert pressure signals into electrical signals and have been widely used in tactile perception,health monitoring,electronic skin,human-machine interaction and other fields.The key to fabricate high performance flexible pressure sensors lies in the selection of force-sensitive materials and the design of device structures.MXene is an emerging class of2D materials whose excellent electrical conductivity makes them ideal candidates for force-sensitive layers.At the same time,the abundant functional groups on its surface are helpful for MXene to combine with other functional materials.In this paper,MXene（Ti₃C₂T_X）nanosheets are used as force-sensitive materials to prepare composite pressure sensors with 2D fiber membranes and three-dimensional（3D）aerogel structures,respectively.They have good sensing performance and can be used in health monitoring,speech recognition,and pressure distribution detection.The main research contents and results are as follows:（1）2D fiber membrane flexible pressure sensor based on chitosan（CS）/polylactic acid（PLA）@MXene.First,the precursor MAX phase Ti₃Al C₂was etched with a mixed solution of hydrochloric acid and lithium fluoride,and then single-layer MXene（Ti₃C₂T_X）nanosheets were obtained by ultrasonic exfoliation.The CS/PLA composite nanofiber membrane was then obtained by electrospinning,and then the MXene was suction filtered onto the fiber membrane.The surfaces of MXene and CS have negative and positive charges,respectively.Therefore,they are combined by electrostatic interaction and MXene can be firmly adsorbed on the fiber membrane.The CS/PLA@MXene-based 2D fiber membrane flexible pressure sensor exhibits high sensitivity(103.55 k Pa^-1),fast response（response time and recovery time of 58 ms and 56ms,respectively）,and good cycling stability（2000 cycles of testing）.It can be used to monitor large-scale human activities in real time,such as bending of fingers,elbows and knees.（2）3D aerogel flexible pressure sensor based on CS/MXene.Through freeze-drying technology,CS/MXene composite aerogels were prepared,which are extremely light and have good resilience.The 3D composite aerogel flexible pressure sensor based on CS/MXene exhibits extremely high sensitivity,reaching 709.38 k Pa^-1 and 252.37 k Pa^-1 in the low-pressure range（less than 1k Pa）and high pressure range（greater than 1 k Pa）,respectively.The sensitivity in both high-pressure and low-pressure range is ahead of the same type of aerogel pressure sensor.Meanwhile,the detection range of the sensor is as high as 20 k Pa,the minimum detection limit is as low as 1.41 Pa,the response and recovery time are 144 ms and 140 ms,respectively,and the performance is almost no degradation after 10000 cycle tests.The above excellent performance not only enables the sensor to detect large-scale pressure signals,such as limb movement and pressure distribution,but also accurately detect small pressures such as pulse and voice.This versatile and flexible pressure sensor greatly broadens the application scope of wearable electronics in many fields such as speech recognition,health monitoring,and human-computer interaction.