| Wearable pressure sensors have been widely used in human-machine interfaces,smart robots and virtual reality technologies in recent years.In order to broaden its application,it is of vital significance to develop flexible pressure sensors with high sensitivity,broad sensing range,short response time and high cycling stability.However,there is a conflict between the high sensitivity and wide sensing range.High-sensitivity pressure sensors usually employ active layer with elastic microstructures to improve the compressibility of active layers.However,the pressure sensors usually exhibited sensitivity decay in high-pressure regime when the elastic microstructures are flattened during the loading process.Therefore,it is still challenging to fabricate pressure sensors with high sensitivity through wide sensing range.Based on this situation,we carried out a series of work to reconcile the contradiction between sensitivity and sensing range,and demonstrate various applications of flexible pressure sensors.The detailed research information is as follows:1.A novel pressure sensor based on inelastic metallic microstructures and flat polymer films with different elastic modulus was fabricated to realize ultra-wide pressure sensing range and high sensitivity of piezoresistive pressure sensors.The sensing performance could be tuned through employing polymers with different elastic modulus.The pressure sensor exhibited ultrawide sensing range,high sensitivity,fast response time and excellent sensing stability,demonstrating potential applications in the detection of human dynamic physiological signals,such as wrist pulse,human movements and gait states.The accelerometer designed based on the GPVDF pressure sensor exhibits a large detection range and has potential applications in human motion recognition and vehicle safety monitoring.2.Bioinspired from the hair-epidermis-dermis structures of human skin,a reduced graphene oxide/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(rGO/PEDOT:PSS)aerogel with skin-like hierarchical structures is proposed to reconcile the conflict between high sensitivity and wide linearity of e-skin tactile sensors.The aerogel is prepared by a combination of in situ chemical reduction and an ion-induced interfacial gelation process on the surface of electrodeposited zinc microstructures.On the basis of these hair-epidermis-dermis hierarchical structures,the as-fabricated e-skin sensors achieve high sensitivity(137.7 kPa-1)and a wide linearity range from 100 Pa to 30 kPa.In addition,the e-skin sensor exhibits excellent ability for precise detection of tiny pressures below 100 Pa,fast response and excellent cycling stability,showing applications in the field of artery monitoring and voice detection.3.A piezoelectric PVDF layer was wrapped around silicon rubber cylinder,which can convert an applied pressure into a horizontal force amplified by flextensional mechanism,causing significantly amplified piezoelectric output voltage and pressure sensing sensitivity compared with conventional flat structure-based pressure sensor.It is worthwhile noted that the uniaxial elongation PVDF film was employed as piezoelectric layer,the improved content of β phase as well as tensile strength of which help to boost the piezoelectric effect and mechanical property of the active layer,increasing the sensitivity and sensing range of the pressure sensor respectively.In addition,the pressure sensor shows ability to analyze the dynamic pressures,including frequency,contact speed and detach speed,exhibiting potentials in human sports.What’s more,the piezoelectric device could be used as generator to charge capacitors and light LEDs.4.To realize dynamic-static pressure detection in high-pressure regime,uniaxial elongation PVDF film was employed as piezoelectric layer,and PU/Au film was employed as piezoresistive layer,both of which were wrapped around the silicon rubber cylinder to fabricate a piezoelectric-piezoresistive sensor for dynamic-static pressure detection.In this work,the piezoresistive sensor exhibited fast response time,large sensing detection range and excellent cycling stability.Based on the above advantages,the sensor can be integrated onto the insole as gait detector,which is expected to show great potential in the fields of human movement analysis and sports rehabilitation. |
