A skin-like pressure sensor array based on silver nanowires and conductive elastomer

In this research, we developed a skin-like tactile sensor array to measure the contact pressure of curved surfaces. The sensor array is laminated into a thin film with 3mm in thickness and can easily be wrapped around a pencil without damaging its skin-like structure. So far we have achieved the array containing 8×16 sensor elements. Its spatial resolution is 1 element per 9mm ² area and it can measure the pressure up to 360kPa. The sensor-array patch contains three layers. The upper and lower layers are polydimethylsiloxane (PDMS) thin films embedded with conductor strips formed by PDMS-based silver nanowires (AgNWs) networks. The middle layer is formed by the mixing of nickel powder with liquid PDMS for contact force measurement. Experimental tests have demonstrated that conductor strips on the upper layer can maintain their resistances around 23Ω with less than 4Ω increase when the tensile strain is up to 50%. Noted is that conductors made with carbon nanotubes can keep its conductivity unchanged for up to only 40% tensile strain. Through fatigue tests, it is observed that the measured AgNWs/PDMS conductor strip exhibits low and stable resistances. This is one of the desired behaviors of the stretchable interconnects for signal transmission. The integrated sensor system can successfully measure the contact pressure induced by objects of different shapes. It can be applied on curved or non-planar surfaces in robots or medical devices for force detection and feedback.