Meter-scale large-area capacitive pressure sensors with fabric with stripe electrodes of conductive polymer-coated fibers

Abstract

We developed meter-scale large-area capacitive fabric pressure sensors for floor sensors to monitor human position. In the fabric pressure sensor, two fabrics with stripe electrodes of conductive polymer-coated fibers woven into them were stacked vertically, and the capacitance changes between the top and bottom stripe electrodes were measured when pressure was applied. By using the die-coating of a conductive polymer and weaving the resultant fibers with meter-scale automatic looming machines, the 1 m × 1 m area with stripe electrodes at a 20 cm pitch was constructed. The pressure sensitivity, which depends on the number of the sensor fibers forming the stripe electrodes, was characterized and optimized to increase output capacitance change. The stripe electrodes with five sensor fibers were found to exhibit a capacitance change of 1.37 pF when pushed with the average foot pressure (i.e., 2.6 N/cm2), which is large enough to detect with conventional capacitance measurement circuits. Finally, pressure sensing with our woven pressure sensor fabric is demonstrated. Our meter-scale pressure sensor fabric technology will be used for bed and floor sensors for monitoring old people in nursing homes and hospitals.