Design And Performance Study Of Polyacrylonitrile-doped Enhanced Flexible Pressure Sensors

As an important part of wearable electronic devices,flexible pressure sensors have attracted much attention.The integration with new technologies such as Internet of Things,cloud computing,block chain can effectively promote the intellectualization of today’s society.However,traditional sensors are usually powered by batteries,which attenuate charge over a long period of time and have a limited lifetime,thus failing to provide a stable and continuous energy supply for devices.Furthermore,although the flexible pressure sensor based on piezoelectric nanogenerator and triboelectric nanogenerator have been developed continuously in recent years,there are still various problems in energy supply,high sensitivity sensing and skin adaptability.In order to solve the above problems,this paper proposes three methods to enhance performances of flexible pressure sensors based on piezoelectricity effect and triboelectricity effect,PAN as the sensitive material,flexible silicon-based polymer as the substrate,and carries out the application exploration of intelligent sensor for human life activities.The main research contents are as follows.（1）Based on the piezoelectric synergistic enhancement effect of polyacrylonitrile and Ba Ti O₃,Ba Ti O₃ promote the conformational transformation of polyacrylonitrile,polyacrylonitrile improve the uniform dispersion of Ba Ti O₃ in the flexible substrate.And a piezoelectric self-driven flexible pressure sensor based on the polyacrylonitrile/Ba Ti O₃/Ecoflex composite film is constructed,which can be used to dynamically monitor the physiological and movement parameters such as plantar pressure,posture,etc.The output voltage/current of polyacrylonitrile/Ba Ti O₃/Ecoflex composite film prepared by mechanical stirring and coating process is 4.5/5.8 times that of Ba Ti O₃/Ecofelx composite film.Under the action of external pressure stress,the pressure sensor can reach a normalized voltage sensitivity and voltage linearity of 0.54 V/N and 0.984,respectively.Furthermore,a human-machine interaction test system is built,which can visually display the pressure distribution and changes of human body monitoring parts in real time according to voltage threshold and different color assignments.（2）Based on the piezoelectric synergistic enhancement effect of polyacrylonitrile and polyvinylidene fluoride,a piezoelectric self-driven flexible pressure sensor composed of silicone rubber,polyacrylonitrile,polyvinylidene fluoride and conductive silver-coated glass microspheres is proposed.The mass ratio of polyacrylonitrile/polyvinylidene fluoride and silicone rubber is up to 4:5 after mixing and vulcanization,which greatly improves the filling ratio of piezoelectric fillers in flexible substrates.The output voltage of the pressure sensor is49 V,which is 2.57 and 3.06 times higher than that of the single-component polyacrylonitrile and polyvinylidene fluoride,respectively.In the range from 0 to 800 k Pa,the sensor retains high voltage and current sensitivities respectively,and its linearity of voltage and current are all close to 0.986.In practical measurements,the designed sensor showed excellent recognition abilities for various gaits and different bending degrees of fingers.Through the home-made signal transmission and storage circuit,an information processing strategy is proposed to realize the intelligent wireless transmission and storage of human posture signals.（3）Based on the combination of piezoelectric effect and triboelectric effect,the triboelectric/piezoelectric charge in different spatial characteristic scales is zero-phase differential coupled.And an all-in-one conformal pressure sensor with a homogeneous integrated triboelectric-piezoelectric hybrid sensor was proposed to ensure its stable response to different external stimulations.Silver-coated glass microspheres and polyacrylonitrile were uniformly filleted into the silicone rubber substrate by hetero-doped method to prepare stretchable electrode layer and piezoelectric layer with flexible conformal characteristics,respectively.Meanwhile,the triboelectric layer was fabricated by the identical silicone rubber,which enables the sensor homogeneously bonded into an all-in-one structure with reliable durability.The test results show that the developed sensor achieves good sensitivity,high linearity,wide measurement range,and can accurately and continuously distinguish various movements.Additionally,with the help of home-made signal acquisition,transmission and control processing circuit,the designed sensors can be deployed in human body and the room as indoor body area network nodes,which successfully applied to the remote tracking of daily dynamic home life and the remote operation of small electrical equipment.In this study,the performance enhancement methods proposed from material doping,process optimization and structure integration solve the problem that the current flexible pressure sensor cannot take into account the high electrical characteristics and skin adaptability,improves the sensitivity and durability of the sensor.This research provides a new strategy for building intelligent sensing and recognition system based on the flexible pressure sensor,and has important application potential in human-machine interaction,physiological analysis and smart medical.