A wearable piezocapacitive pressure sensor with a single layer of silver nanowire-based elastomeric composite electrodes

A highly stretchable and transparent pressure sensor based on a single layer silver nanowire (AgNW) electrode was successfully fabricated. In order to achieve this, we synthesized a stretchable and transparent adhesive, polyurethane urea (PUU), which was designed to firmly adhere to the AgNWs by incorporating 2,2-bis(hydroxymethyl)butyric acid with a carboxylic group. A patterned AgNW-based sensing electrode could be completely transferred to a PUU film deposited on a poly(dimethylsiloxane) (PDMS) substrate, resulting in a AgNW/PUU/PDMS pressure-sensitive capacitor. The capacitance was developed on a AgNW tandem compound electrode pattern by the fringing effect, which decreased with increasing pressure applied to the surface of the sensor. The sensitivity did not significantly deteriorate, even when the sensor was stretched up to a strain of 35% or when the stretching was cycled up to 10 000 times. A wearable acupressure sensor with a pressure sensitive matrix of nine pixels was successfully demonstrated.