Development of a Novel Direct Ink Writable, Skin-mounted, Wearable Strain Sensor for Human Motion Monitoring
Abstract
Flexible strain sensors have seen significant research for applications in motion monitoring, soft robotics, and wearable electronics. However, issues like conformability, recyclability, and long-term stretchability remain. This thesis introduces a novel, sustainable composite strain sensor made from polyvinyl alcohol (PVA), silk fibroin (SF), and multi-walled carbon nanotubes (MWCNT) for wearable motion sensing. Inspired by viscoelastic silly putty, the addition of hygroscopic calcium chloride (CaCl2) allows the sensor to absorb ambient moisture and conform to various surfaces while maintaining stretchability and sensitivity. Using direct ink writing (DIW) for 3D printing, specific sensor geometries are created for easy application to three-dimensional substrates, such as human skin. This work covers material synthesis, sensor fabrication, mechanical and electrical performance testing, material characterization, and the sensor’s DIW printability. The sensor offers longevity, moldability, self-healability, and gauge factors from 0.1 to 0.8. This thesis also examines different PVA to SF ratios and ink viscoelastic properties at various temperatures, enhancing its usability in diverse environments.