Structural design of flexible interdigital capacitor based upon 3D printing and spraying process

Abstract

Traditional substrates of metallic interdigital electrodes (IEs) are rigid and undeformable, flexible interdigital capacitors are therefore appealing as strain sensors. In this study, interdigital capacitors were parametrically designed by 3D printing and encapsulated by spraying process. The interdigital circuits of the structure were printed with conductive silicone rubber filled with silver-coated glass fiber and carbon fiber, and the circuits were encapsulated with polydimethylsiloxane. Herein, the interdigital-flexible structures were parametrically designed and firstly served as capacitive sensor, namely flexible interdigital capacitive sensors (FICSs). The spaces between IEs, are extremely sensitive to strain, therefore provide the capacitors with excellent electromechanical behaviors. The optimized FICS benefited for a wide working range of strain (0%∼45%), high sensitivity (gauge factor = 2.7) to a tiny strain of 0.3%, stable working duration at different stretching speeds (18 mm min−1, 36 mm min−1 and 72 mm min−1), prolonged service life (>800 cycles), as well as excellent capability to detect human movement (bulging, grasping and bending). Response mechanism of the FICS was modeled based upon its microstructure evolution, including the distances between IEs and the fillers migration. The printed FICSs with optimized structure provide a comprehensive thought in the design of electronics, further would inspire the branch of 3D printed electronics.