Effect of Additive Manufacturing on beta-Phase Poly(Vinylidene Fluoride)-Based Capacitive Temperature Sensors

Additive manufacturing, commonly known as 3D printing, significantly simplifies the manufacturing process for soft electronics. This work demonstrates the feasibility of a fully 3D-printed flexible poly(vinylidene fluoride) (PVdF) capacitive temperature sensor. The sensor is constructed using fused deposition modeling (FDM)-printed PVdF film as the dielectric (thickness approximate to 180-280 mu m) sandwiched between two parallel Direct Ink Writing (DIW) printed silver electrodes (entire device thickness approximate to 200-380 mu m). The motion of the nozzle can facilitate mechanical drawing to the molten PVdF filament, which is a necessary condition to increase the beta-phase content (critical for the sensitivity of the sensor). With optimized printing parameters, the highest beta-phase content (21.30%) is achieved when printing with a nozzle temperature of 200 degrees C and a print speed of 70 mm s(-1). The research demonstrates the application of the device as a temperature sensor by applying heating-and-cooling cycles from room temperature (25 degrees C) up to 140 degrees C while measuring the capacitance as a function of frequency under different temperatures. The sensor exhibits a stable sensitivity of 3 pF degrees C-1 at 10(2) Hz and higher frequencies and improved sensitivities at frequencies higher than 10(2) Hz after dielectric polarization via the corona poling method.