High-Performance\nAuxetic Bilayer Conductive Mesh-Based\nMulti-Material Integrated Stretchable Strain Sensors

Abstract

High-performance\nstretchable strain sensors, particularly those\nwith high sensitivity and broad sensing range, are highly important\nfor wearable devices. Herein, a novel auxetic bilayer conductive mesh\nstrain sensor (ABSS), composed of multi-hardness silicones, is proposed\nand fabricated by the direct ink writing 3D printing and ink spraying\ntechnique. The bilayer conductive mesh comprises a thin layer of high-conductive\nand crack-prone single-walled carbon nanotubes (SWCNTs) coated on\na stretchable carbon-black-doped Ecoflex silicone rubber (CB/Ecoflex)\nmesh. The former serves as the dominant sensing material by generating\nSWCNT cracks in the full strain range, while the latter mainly plays\nthe roles of both generating the resistance change and maintaining\nthe conductive paths under high strain conditions. The presence of\nhigh-hardness auxetic frame contributes to the formation of longitudinal\nSWCNT cracks on transverse meshes, enhancing the sensitivity of the\nsensors. It is shown that the synergistic effect of the bilayer conductive\nmesh, strain concentration, and auxetic deformation strategy endow\nABSS with a high gauge factor (∼ 13.4) that is 6.6 times larger\nthan that of the common sensor. Additionally, this study demonstrates\nthe superior sensing performance of the ABSS for wearable applications\nincluding swallowing recognition, respiration monitoring, and joint\nmovement detection.