A 3D-Printed Flexible Radio Frequency Strain Sensor Based on Complementary Split Ring Resonator

Abstract

This paper presents a 3D printed flexible strain sensor, and the resonant frequency of the sensor changes with its own deformation. The sensor is a coplanar waveguide composed of a conductive material and a flexible substrate material with an open ring resonator structure. Simulation results built on solid mechanics and radio frequency show that the resonant frequency of the designed resonator will be changed as its stretched length transformed. The sensor is manufactured by a self-developed 3D printing platform, which uses the droplet spray process to print conductive liquid metal materials, compared with the traditional process of using a syringe, the printing process has better operability and accuracy. The prepared sensor has a maximum strain range <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varepsilon ={115}$ </tex-math></inline-formula> %, and the goodness of fit ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{R}^{{2}}$ </tex-math></inline-formula> ) of the relationship between the strain length change and the resonant frequency change is higher than 0.995. It can be seen that the sensor has excellent stretchability and linearity.