A single-layer stitched electrotextile as flexible pressure mapping sensor

In this paper, a stitched fabric for decoding the pressure distribution information by means of resistive sensing is introduced. The proposed fabric-structured sensor is constructed by a distributed resistive array of two orthogonally contacted electrical conductive yarns system, which needs not any external sensing elements to be attached on the fabric. The conductive yarns served as the sensing and wiring elements simultaneously, which in turn simplify the fabrication process and decrease the cost, make the production of large area flexible pressure sensor possible. The topology of the sensing elements distributed on the fabric can be set by stitching the conductive yarn on the substrate fabric by sewing or embroidery machine. The location and pressure applied on the fabric can be obtained by detecting the position where the change of the resistances occurs between two embroidered yarns system. Meanwhile, the magnitude of the pressure can be acquired by measuring the variations of the resistance under pressure. Coating is applied on the contact points of the two yarns system to increase the sensitivity and stability. It is found from the experimental results that the sensitivity and stability are improved dramatically after coating. The resistance vs. pressure exhibits a nonlinear two stages mode and the contacting resistance is unstable at small pressure region. The electronics system that picks up the signal of the resistance matrix is also introduced. Flexible, robust, light weight, and breathable provide the sensor advantages to be used as wearable sensors. Meanwhile, easy fabrication and low costs make large area sensing such as sensing carpet possible.