Pressure monitoring inside a polymer tube based on a dielectric elastomer membrane sensor

Abstract

Dielectric Elastomers (DE) represent an attractive technology for the realization of low cost and highly stretchable capacitive sensors. The novel contribution of this work is the development of a nonintrusive DE sensor (DES) for polymer tubes, capable of measuring pressure levels inside the tube up to 60 bar. A novel solution is proposed to perform the measurement, in which a membrane DES is wrapped around the tube. While the tube expands due to high pressure, the DES capacitance increases accordingly. To perform system characterization, a test rig is designed to measure the expansion of a polymer tube while applying an external pressure. Several experiments are performed to obtain the tube characteristics at different pressure levels. Based on theoretical predictions and tube characterization, membrane DES are developed, manufactured, and then characterized. Finally, it is shown how the change in capacitance can be related to the pressure inside the tube, allowing to obtain the desired measurement. The performance of the device is assessed by means of several experiments.