Enhancing sensitivity in wireless capacitive pressure sensors via highly flexible LC circuits utilizing porous polydimethylsiloxane dielectric layer

Abstract

In this study, we introduce a highly flexible LC circuit-based wireless capacitive pressure sensor (CPS) that utilizes porous polydimethylsiloxane (PDMS) as a dielectric layer, demonstrating its transformative potential in tactile sensing, physiological monitoring, and flexible electronics. To optimize sensor performance, various porous PDMS thin films (100 mu m) with different porosities (ranging from 0 % to 75 %) were prepared using a novel steaming method, and their properties were thoroughly analyzed using field emission scanning electron microscopy (FE-SEM) and capacitance measurements. Remarkably, the sensor with a 75 % porous PDMS film demonstrated enhanced sensitivity up to 11 times compared to the 0 % porous (pristine) PDMS film when subjected to a 300 g weight. High sensitivities of 0.046 kPa"-1, 0.036 kPa"-1, and 0.028 kPa"-1 were attained for the pressure sensor in the pressure ranges of 0-9.8 kPa, 0-19.6 kPa, and up to 29.4 kPa, respectively. Additionally, a real-time resonance frequency analysis was conducted using a network analyzer, allowing the detection of tiny pressure changes in an artificial blood vessel. Finally, the flexibility of the wireless CPS was investigated by studying various parameters, including body temperature, facial expressions such as smiling, selected speech characters (M, N, T, L), and swallowing actions.