Research On 3D Printing Process Of Flexible Sensor Based On Piezoelectric Microjet And Pneumatic Extrusion

Compared with the existing sensors,the flexibility,malleability and foldability of the flexible sensor make it widely used in many emerging fields.Compared with the traditional fabrication methods of flexible sensors such as photolithography and mold reversal,the fabrication method based on three-dimensional printing has the advantages of low cost,easy customization and easy preparation of three-dimensional structures,and has become an important research direction of flexible sensor.However,existing flexible sensor fabrication solutions generally only use a single three-dimensional printing process to complete the manufacturing of sensitive components or packages,which are difficult to simultaneously take advantages of multiple processes and cannot achieve integrated sensor formation.This research has developed a set of 3D printing system for flexible sensor which is based on the composite process of piezoelectric micro-injection and air pressure extrusion.In order to verify the feasibility of the developed composite fabrication process for the flexible sensors,the research designed a new type of flexible radio frequency(RF)strain sensor,fabricated the flexible sensor through the built molding system,and compared the measured performance with the simulated performance.The main research of this paper is as follows:(1)The principle of the flexible radio frequency strain sensor is analyzed.Based on the correlation between the geometric dimensions and the resonant frequency of the resonator,a flexible RF strain sensor was designed.The sensor can be regarded as a CPW(coplanar waveguide)with a CSRR(complementary split ring resonator)structure.The use of CSRR structure and CPW effectively reduces the volume of the sensor.The finite element radio frequency and mechanical simulation results of the sensor model show that the designed sensor has obvious resonance in the predetermined frequency band.With the increase of the stretch length,the resonance frequency of the sensor will decrease significantly and the relationship between the two is approximately linear.(2)In order to realize the integrated fabrication of flexible sensors,a set of 3D printing platform based on composite process was built in this research.The piezoelectric micro-jet and air pressure extrusion process suitable for low-viscosity liquids and high-viscosity colloids is used for printing of sensor molding materials with different viscosities.Use ARM core ATSAME70Q20B-AN 32-bit microprocessor as the core to design the processor module,power supply module and communication module of the control board.Based on the control board,the main functions of the electrical control system such as the movement of the forming platform,the switching and spraying of nozzles,and the heating of the bottom plate are realized.The electrical control system with the air pressure control system and the host computer control system constituted the complete molding system.(3)The flexible radio frequency strain sensor designed in this subject selects liquid metal(gallium indium eutectic alloy,EGa In)and platinum-catalyzed silicone rubber(Ecoflex00-30)as conductive and packaging materials,respectively.The Ecoflex00-30 mixed encapsulation material with viscosity suitable for air pressure extrusion is configured by doping nano-silica.The optimal printing parameters of the composite process were tested,and the designed flexible radio frequency strain sensor was prepared based on the optimal printing parameters.The strain range,linearity and sensitivity of the fabricated strain sensor were tested,and the test results were better than the model simulation,which verified the superiority of the composite process molding platform built for the preparation of flexible sensors.The 3D printing process of flexible sensor based on piezoelectric micro-jet and air pressure extrusion proposed in this research will promote the further development of flexible electronics.