Simultaneous pressure and strain sensing with stretchable capacitive sensors

Abstract

Abstract Stretchable pressure and strain sensors have been the focus of extensive research in recent years due to their significant potential. Several studies have explored different approaches to enhance their performance. However, most of these works focus on separate sensors for each purpose, and the research investigating the simultaneous measurement of both pressure and strain is limited. This paper presents a stretchable capacitive sensor capable of simultaneously measuring pressure (up to 245.5 kPa) and strain (up to 40%). Our design leverages the conductivity and piezoresistivity of an inexpensive carbon black and Ecoflex 00-30 composite, which serves as both the strain-detection element and the electrodes for the capacitive pressure detection element. To characterize the sensor’s response to both stimuli, we apply a range of pressures and strains concurrently and observed the corresponding capacitance and resistance changes. The characterization results show that the measured resistance change is primarily determined by the applied strain, while the measured capacitance change is dependent on both the pressure and the strain. A computationally efficient polynomial model is identified to capture the capacitance change as a joint function of the pressure and strain inputs, which enables the estimation of the pressure once the strain is inferred from the resistance measurement. Validation experiments show that the approach to simultaneous measurement of strain and pressure is feasible and effective. The proposed work holds promise for advances in soft robotics, wearable electronics, and biomedical monitoring.