Construction Of Polypyrrole-based Hybrid Conductive Network And Its Application In Flexible Sensor

With the rapid development of electronic equipment,people’s attention to health has also continued to rise,which has prompted the rapid development of electronic skin.As an important component of electronic skin,flexible sensor has also received widespread attention.However,the traditional tactile sensor often has limited sensitivity or insufficient linearity in a wide range of pressure or compressive strain.For the flexible strain sensor,due to the limitation of traditional rigid conductive materials,the conventional strain sensor has a narrow sensing area or a single sensing function,which is difficult to meet the practical needs,thus limiting the application of the sensor.Polypyrrole(PPy),as a kind of conductive polymer,has many excellent properties,such as simple and controllable synthesis method,non-toxic,high conductivity,and is widely used in flexible sensors.To resolve the existing problems in the conventional pressure sensor and strain sensor,this work puts forward some solutions from rational design of structures and selection of advanced materials.The main research contents are as follows:(1)Recently,wearable piezoresistive tactile sensors have attracted considerable attention owing to their potential applications,ranging from electronic skin to human-machine interaction.However,it is still difficult to mitigate the trade-off between sensitivity and linearity.Inspired by the hierarchical and gradient structures in natural systems,a versatile resistive pressure-sensing platform with controllable stress transfer and contact areas was fabricated by designing gradient styrene-butadiene-styrene triblock copolymer(SBS)sponges followed by the deposition of silver nanoparticles(Ag NPs)and polypyrrole(PPy).The synergistic effect of gradient stiffness and conductivity gradient porous structure endows biomimetic tactile sensors with excellent sensing performance,which is demonstrated by large sensing range(～80%),large linear range(～72%),high sensitivity(～1.07),low hysteresis behavior(7.66%),fast response time(177 ms),and excellent durability(more than1100 cycles).Important applications of tactile sensors,including wrist-pulse-signal detection,speech recognition,finger bending,and tactile interfaces,have been successfully demonstrated.This conceptually simple but powerful approach can be applied to other nanomaterial systems to develop next-generation electronics.(2)Human-machine interactive platforms that could sense mechanical stimuli visually and digitally are highly desirable,however,most existing interactive devices can not satisfy the demands of tactile feedback and extended integration due to their complex integration procedure and limited visualization flexibility.Inspired by the mechanoluminescence(ML)function of cephalopod skin and sensitive perception of micro-cracked slit-organ,a bioinspired stretchable interactive platform was developed by designing poly(styrene-block-butadiene-block-styrene)(SBS)/fluorescent molecule(SFM)composite followed by the in-situ polymerization of pyrrole(Py)and deposition of carbon nanotubes(CNTs)through spray-coating approach,which possessed simple multilayered structure and quantitatively sensed the applied strains via monitoring the variations of digital electrical resistance and visual fluorescence intensity.Taking advantage of the strain-dependent microstructures from the synergistic interactions of rigid PPy/CNTs conductive layer and stretchable SFM,the SFM/PPy/CNTs-based strain sensor exhibited excellent strain-sensing performance manifested by high gauge factor(GF=2.64×10~4),wide sensing range(～270%),fast response/recovery time(～125/27ms),excellent stability(>1600 cycles),and sensitive ML characteristics under ultraviolet illumination.Benefiting from the novel fusion of digital data and visual images,important applications,including detection of wrist pulse and finger bending,and information dual-encryption,have been demonstrated.This work demonstrated the superiority of advanced structures and materials to realize superior applications,showing the feasibility of advanced materials and structures in wearable electronics.