Development of a nonintrusive pressure sensor for polymer tubes based on dielectric elastomer membranes

Abstract

In this work, a nonintrusive pressure sensor for contrast fluid injection in medical applications is developed, based on a dielectric elastomer (DE) membrane transducer. A DE is essentially a highly deformable capacitor, consisting of a thin elastomer membrane coated with compliant electrodes. A novel solution is proposed to perform a nonintrusive pressure measurement, in which a DE membrane is wrapped around the injection tube (patient line). While pressure is applied to the tube it expands, leading to an extension of the sensor and therefore to a significant increase in DE capacitance. First, a test rig is designed in order to measure the expansion of the polymer tube during pressure application. Multiple experiments are then performed to evaluate the tube deformation at different pressure levels. Subsequently, analytical models are developed for both fabric-reinforced injection tube and DE sensor, in order to predict the resulting capacitive change of the DE as well as to approximate the mechanical properties of the tube. Based on model predictions and tube characterization results, membrane DEs with different sensor geometries are developed, manufactured, and characterized. The sensor performance is finally assessed by means of several experiments, showing remarkable performance for pressures up to 62 bar.