2D Percolation Design with Conductive Microparticles for Low-Strain Detection in a Stretchable Sensor

Abstract

Although a variety of stretchable strain sensors based on electrical percolation have been reported, stretchable sensors detecting low strains have been rarely demonstrated. This is because large stretchability of a strain sensor conflicts with high strain resolution at low strains. Here, the electrical percolation into 2D is confined and a strain sensor that is highly sensitive at low strains and simultaneously highly stretchable is presented. The 2D confinement of the electrical percolation is accomplished by a close-packed monolayer assembly of conductive microparticles (MPs) on an elastomer substrate. The current profiles of the MP monolayer at low strains are in situ visualized using conductive atomic force microscopy. When the lattice of the MP monolayer is aligned vertically to the strain direction, the resistance is highly sensitive to low-strain deformations (epsilon = 0 - 0.05), but the sensor has reasonable stretchability (epsilon = 0.3). The simultaneous achievement of the high sensitivity at low strains and the reasonable stretchability is explained by the relationship between the strain-dependent current profile and the relative position changes of the MPs. A high-precision pulse sensor clearly showing the representative peaks is demonstrated.