Design,Fabrication And Properties Of Flexible Triboelectric Self-Powered Pressure Sensors

With the rapid development of wearable electronic technology,sensors,as one of their most important components,have become a hot research topic.Flexible pressure sensors can be attached to different parts of the human body to achieve real-time monitoring of the human body’s movement and multiple physiological health information,which has an excellent development prospect in the field of human-computer interaction and health monitoring.However,the service life of traditional pressure sensors is limited by external power sources,and the problem of poor battery life has become a bottleneck restricting their development.The self-powered pressure sensors based on the triboelectric power generation effect can convert mechanical energy into electrical energy and provide feedback on all information related to external forces.Coupled with appropriate energy storage and power management technologies,it can effectively extend the continuous working time of the sensing system.However,there are still some problems that need to be solved urgently for triboelectric pressure sensors.Firstly,its sensing signals are extremely susceptible to external interference,seriously reducing reliability and stability;Secondly,due to the complex micro/nano processing technology,the sensitivity and other performance of frictional electric pressure sensors still need to be improved.Therefore,developing a strategy that can eliminate the impact of external charged objects and the environmental atmosphere on the sensing signals,thereby improving the long-term stability of the triboelectric pressure sensors is the first research point of this paper;The second research point of this paper is to design a dielectric layer that is easy to prepare and used to improve the sensing performance of a triboelectric pressure sensor,allowing the sensor to have extremely high sensitivity in the low-pressure range,while increasing the maximum pressure that can be monitored and the corresponding sensitivity.Based on the above research points,starting from optimizing the overall sensing performance and wearable application requirements of friction electric pressure sensors,this paper developed flexible and stretchable functional materials for triboelectric pressure sensors,and studied the structure-activity relationship between the mechanical properties of the dielectric layer and the sensing performance,thereby constructing a flexible friction electric pressure sensor with high sensitivity,wide pressure detection range,and wonderful anti-interference ability.The main results are as follows:（1）A high-performance flexible triboelectric pressure sensor based on liquid metal（LM-TPS）has been designed and prepared.Firstly,a tapered structure that is easy to compress was constructed on the surface of the silicone rubber triboelectric layer through laser printing technology and reverse molding method to enhance the amplitude of change in the distance between the triboelectric layers when the sensor is under pressure,resulting in a sensitivity of 1.70 kPa^-1 at the low-pressure range of 0.52～4.8 kPa,and a sensitivity of 0.63 kPa^-1 at the high-pressure range of 4.8～116 kPa.By heating and melting the liquid metal（LM-48,bismuth-indium-tin-lead-cadmium alloy）electrode with a melting point of 48℃,the sensitivity under high pressure can be improved,enabling it to flexibly meet the high sensitivity requirements under different pressure ranges.The mechanism of the oxide layer existing at the interface between the LM-48 electrode and silicone rubber to enhance the sensing signal strength and signal-to-noise ratio was explored.A conductive shielding layer with ultra-high elongation（760%）was prepared by uniformly mixing liquid metal（Galinstan,gallium-indium-tin alloy）with a melting point of-19℃ and organic silicone rubber.The resistance during the entire stretching process was maintained below 0.25 Ω,and the electromagnetic interference shielding efficiency（EMI SE）reached over 10 dB.After the sensor was completely covered by this shielding layer,it was almost unaffected by other objects and the charges on the packaging surface.The sensing signal could maintain stability at a humidity of 35%RH to 80%RH,and there was no significant change in the sensing signal within 2 months.Finally,the pressure sensor is fixed to different parts of the human body to monitor real-time physiological signals such as human joint motion,pulse,and respiration.It can also be used for accurate gesture recognition,demonstrating its application prospects in the field of human-computer interaction and physiological health monitoring.（2）A flexible triboelectric patch（FTEP）with a porous reinforced structure was designed and prepared for remote physiological signal monitoring.A silicone rubber triboelectric layer with a porous reinforcement network structure was constructed by using a polyurethane（PU）porous sponge as a template and coating its surface and inner wall with a diluted silicone rubber solution.The triboelectric layer has great compression space and overall mechanical properties are enhanced under pressure,enabling the prepared FTEP to achieve an ultra-high pressure sensing sensitivity of 6.20 kPa^-1 in a wide pressure range of 0.04～4.25 kPa,and the silicone rubber on the surface of the triboelectric layer,as an excellent negative triboelectrification material,can increase the voltage signal strength by more than 200%,significantly increasing the signal-to-noise ratio of pressure sensing.A mechanoelectrical coupling model was constructed to study the structure-activity relationship between the mechanical properties and sensing properties of the dielectric layer.Theoretical calculations showed that the sensitivity would be affected by the equivalent stiffness coefficient of the dielectric layer,which theoretically supported the experimental results.Finally,the impedance mismatch problem has been solved through four steps:signal amplification,low-pass filtering,data acquisition,and data processing.The FTEP is fixed to different parts of the human body,which can monitor both high pressures such as plantar pressure,and weak physiological signals such as pulse waves.At the same time,a wearable Internet of Healthcare（IoH）system for pulse wave detection has been proposed,which can provide direct and realtime pulse waves to medical personnel and users by transmitting the processed signal to the mobile end through Bluetooth,demonstrating its application prospects in dynamically personalized cardiovascular disease prevention and monitoring.