Multilayered Fabric Pressure Sensor for Real-Time Piezo-Impedance Imaging of Pressure Distribution

We developed a multilayer fabric pressure distribution sensor, sensor interface, and electrical impedance imaging system for real-time pressure distribution imaging. The new pressure distribution sensor consists of conductive elastic fabrics and layered polyurethane (PU) nanoweb containing air shells to increase its pressure sensitivity. The sensitivity and hysteresis of three fabric sensors with different layer structures were measured to compare their electromechanical properties as a pressure sensor. The sensor with one PU nanoweb layer sandwiched by two conductive elastic fabrics showed the best performance and was chosen for real-time pressure distribution imaging experiments. The imaging system acquired the electrical impedance data along the boundary of the sensor by injecting ac currents and measuring induced voltages on its boundary. This enabled the system to detect both piezo-resistance and piezo-capacitance changes in the sensing area of the sensor subject to a vertically applied pressure distribution on the top surface of the sensor. Applying an impedance image reconstruction algorithm to the collected boundary data, impedance images of the sensing area were reconstructed in real time, which corresponded to the applied pressure distribution. Quantitative analyses of reconstructed impedance images were performed to evaluate the overall performance of the developed multilayer fabric pressure distribution sensor. The fabric sensor and the imaging system provide a new way of quantitatively visualizing pressure distributions in real time.