Fabrication And Properties Study Of Piezoelectric Composite Film Based Flexible Pressure Sensor

With the rapid development of information technology,the application of Internet of Things is in the ascendant,and various emerging technologies have sprung up.Wearable electronics are one of the most crucial application inthe field of the Internet of Things,which are of great significance for medical care monitoring and human-computer interaction.The research object of this article is a flexible piezoelectric pressure sensor,aims at developing piezoelectric composite film based pressure sensor composed of inorganic piezoelectric ceramic materials such as barium titanate（Ba Ti O₃,BTO）,lead magnesium niobate titanate（PMN-PT）and organic piezoelectric polymer material,i.e.polyvinylidene difluoride Ethylene（PVDF）.Herein,the polydopamine（PDA）surface coating was introduced for the modification of BTO,and the effect of PDA doping amounts on the sensing performance including piezoelectric response,dielectric properties and mechanical capability was studied.In addition,since piezoelectric materials with high-voltage electrical coefficients are the main factor to improve the performance of piezoelectric sensors,a PMN-PT ceramic material with a piezoelectric coefficient up to 2000 p C/N together with MXene were employed to develop high-performance pressure sensor.Connective-tissue inspired piezoelectric composite（CIPC）film and MXene/PMN-PT/PVDF nanofiber composite film were prepared by electrospinning technology,respectively,where a"sandwich"structure was adopted for the wearable flexible pressure sensor.The main research results and innovation of this work are listed as follows:1.The CIPC-based pressure sensor with various PDA doping amount was prepared by electrospinning method.Firstly,the influence of PDA coating amount on the piezoelectric,dielectric and mechanical properties of electrospun CIPC nanofibers was analyzed by phase-field simulation,in which the optimal doping amount of PDA was 1.44Vf%.Then the piezoelectric,dielectric,and mechanical properties of the CIPC film were studied through experiments.The results followed a similar trend of the simulation,with a slight discrepancy in terms of optimal value.The optimal doping amount in experiment was 2.15 Vf%.Futhermore,the CIPC-based sensors demonstrate an excellent performance on human health monitoring,human-machine interfacing,voice regonition and external dynamic force detection.2.The MXene/PMN-PT/PVDF flexible piezoelectric nanofiber based pressure sensor was prepared by the electrospinning method with different MXene doping concentration and diverse spinning time.The impact of MXene doping concentration and spinning time on the piezoelectric and dielectric properties of electrospun MXene/PMN-PT/PVDF nanofibers was systematically analyzed,where the optimal doping concentration of MXene and spinning time was 2.5 wt%and 2 h,respectively.Then the piezoelectric,dielectric and mechanical properties of the piezoelectric composite film are studied through experiments,which are basically consistent with the simulation results.Moreover,the MXene/PMN-PT/PVDF nanofiber sensors exhibit good performance on the self-powered gesture identification on keyboard and touchscreen of smart phone.Therefore,the nanofiber pressure sensors demonstrate great application potential in the fields of human-computer interaction,electronic skin,personal healthcare,smart robots,and portable wearable devices.