Piezoresistive Sensor Based On Ti₃C₂-MXenes

Pressure sensor is an important component of electronic touch display,intelligent health care and human-computer interaction system.As a type of pressure sensor,piezoresistive sensor has attracted extensive research because of its low cost,simple structure and good frequency response.At present,a new two-dimensional material MXenes(transition metal carbides,nitrides or carbonitrides)has been used in piezoresistive sensors due to its high conductivity and large specific surface area.The new piezoresistive sensor based on MXenes material has been proved to be a high-performance pressure sensor,which has advantages in response time,stability,sensitivity,and detection range.Piezoresistive sensor based on MXenes consists of the electrode,sensing layer and packaging layer.The preparation of sensing layer with micro/nano-structures has been proved to be an effective method to improve the sensitivity of the sensor.However,most of the fabrication methods of micro/nano-structures are complex,and the detection sensitivity of low pressure is weak.The electrical characteristics of active thin film transistor in subthreshold and saturation region can be used to improve the detection accuracy in low pressure range by integrating active thin film transistor with the piezoresistive sensor.Meanwhile,the packaging layer is also of great significance to the sensitivity and stability of the sensor.Therefore,it is necessary to explore a piezoresistive sensor with novel,simple micro/nano-structure,reliable packaging layer,and integrated with thin film transistor.The main works of this paper are as follows:(1)The piezoresistive material Ti₃C₂-MXenes is prepared by chemical liquid etching,and two kinds of piezoresistive sensors with stress crack micro/nano-structure and fiber paper micro/nano-structure are fabricated.The influence of micro/nano-structure on the performance of the sensor is also studied.The sensor with crack structure shows the sensitivity of 516.74 kpa^-1,the response/recovery time of 15 ms/25ms,and durability for 1400 sensing cycles.The sensor with fiber paper micro/nano-structure shows the sensitivity of 7.4 kpa^-1,the response/recovery time of 26 ms/26 ms,and durability for 1400 sensing cycles.(2)Piezoresistive sensors based on glass,PI and PDMS packaging materials are fabricated,and effects of the materials on the sensors are compared and analyzed.The PI packaged sensor shows the sensitivity of 0.11 kpa^-1,the response/recovery time of100 ms/100 ms,and durability for 1400 sensing cycles.The PDMS packaged sensor shows the sensitivity of 8.01 kpa^-1,the response/recovery time of 25 ms/25 ms,and durability for 1900 sensing cycles.(3)The piezoresistive sensor integrated with active thin film transistors is designed based on the amplified current characteristics of transistors.The integrated piezoresistive sensor is fabricated by analyzing the principle of the sensor and developing lithography micro/nano manufacturing layout.The highest sensitivity of the integrated piezoresistive sensor based on MXenes/fiber paper micro/nano-structure and glass package is 4636.1 kpa^-1,which is 626.5 times higher than that of the single piezoresistive sensor.The highest sensitivity of the integrated sensor based on MXenes/fiber paper micro/nano-structure and PDMS package is 7953.7 kpa^-1,which is 993times higher than that of the single piezoresistive sensor.The durability of both sensors is more than 1500 sensing cycles.