Design And Performance Research Of Wearable Piezoelectro-triboelectric Composite Sensor

Piezoelectric-triboelectric energy conversion technology can convert mechanical energy into electrical energy to power electronic components,or be used as a self-powered sensor to detect the physiological state of the human body.In this paper,the doping and thin film technology in the MEMS process is used to prepare nanocomposite electrodes,and a wearable sensor is designed to detect human pulse and cadence signals by using this electrode.This article explores the performance of this sensor through physical field tests such as no field,temperature field,ultraviolet field,magnetic field,and compound field,as well as human body wear experiments.The piezoelectric effect of Polyvinylidene Fluoride(PVDF)material is studied,and its piezoelectric conversion mechanism is analyzed.The force-electric conversion model of piezoelectric cantilever beam is established from the perspective of dynamics,and the electromechanical coupling model of piezoelectric beam is derived by using the lumped parameter method.The generation mechanism of friction power generation is analyzed,and its equivalent capacitance model is established.The electromechanical coupling relationship between the output voltage and the separation distance of the friction layer is derived,which provides a theoretical basis for the design of wearable sensors.The finite element model of piezoelectric cantilever beam and triboelectric element is constructed.The parameterized design of the piezoelectric cantilever beam is completed with copper as the base material,and the output voltage,stability,hysteresis characteristics and sensitivity of the piezoelectric beam in each physical field under the first-order resonance frequency are analyzed.The simulation studies the influence of the selection of friction layer materials,the size and the separation distance of the friction layers on the performance indicators of the triboelectric unit under various physical field conditions,which lays the foundation for the design and application of the composite sensor.Based on the nano-particle doping and thin film technology in MEMS preparation process,the preparation of nano-composite electrode is completed.It is combined with PVDF piezoelectric material,Polydimethylsiloxane(PDMS)and Al friction electrical material to form the piezoelectric unit and friction electrical unit of the bracelet structure composite sensor.The signal processing circuit is designed,and the filtering effect and cutoff frequency are simulated and analyzed.The vibration frequency matching test of piezoelectric cantilever beam is carried out,and the comparative experiment of nano-composite electrode specimen and general single Cu foil electrode specimen is completed.The experimental results show that the sensitivity of the nano-composite electrode specimen is 1.4V/g,which is 1.67 times that of the single electrode specimen,the stability is 1.93?2.29 times,the hysteresis error is reduced by more than 50%,and the output performance is improved nearly twice.In addition,the combination of the piezoelectric unit and the signal processing circuit realizes the effective detection of the human pulse signal.The performance test of the triboelectric unit is carried out,and the influence of the different separation distance of the friction layer material on its performance indicators under various physical fields is studied.The experimental results show that the sensitivity of the nano-composite electrode specimen is10%?30% higher than that of the single electrode specimen,and the stability is1.3?4.54 times higher than that of the single electrode specimen.The output performance of the nano-composite electrode specimen is improved to some extent,and the hysteresis characteristics are well suppressed.Through the wearable experiment test,the triboelectric unit has realized the effective recognition of the stride frequency signal.The wearable piezoelectric-triboelectric composite sensor studied in this paper uses nanoparticle doping and thin film technology to effectively overcome the shortcomings of single-electrode sensors such as low sensitivity,poor stability,large hysteresis error,and low output voltage.The anti-interference ability of the sensor is improved,which provides theoretical and experimental basis for the application of piezoelectric and triboelectric mechanisms in wearable devices.