Outward- And inward-distinguishable bending sensor with silver nanowires sandwiched between polydimethylsiloxane layers

A bending sensor having a structure in which silver nanowires (AgNWs) are located between polydimethylsiloxane (PDMS) layers, which can distinguish outward bending and inward bending directions, was fabricated. As the absolute value of curvature increased during outward bending, the relative change in resistance increased, and at a curvature of 0.24 mm-1, it increased by 36% compared to the flat state. In inward bending, the relative change in resistance decreased as the curvature increased. In order to analyze the reason for the opposite resistance change depending on the bending direction, the birefringence of the PDMS polymer during bending was measured using the Stokes polarimetry method. Due to the different locations of the neutral plane with the asymmetric position of the AgNWs, the PDMS polymers were aligned differently. The opposite resistance change during outward and inward bending could be explained as the effect of the different realignments of the AgNWs imprinted by the PDMS polymers.