Three-dimensional morphology in localized Joule heating-induced structured films for enhanced sensitivity in soft pressure sensors

Manufacturing well-designed three-dimensional (3D) structures on the surface a soft elastomer is essential for achieving a highly sensitive soft pressure sensor and for pursuing advanced applications. While soft pressure sensors with 3D structures have previously been developed through methods such as prefabricated micro-pattern molds and elastomer replication, challenges such as limited geometric flexibility and the necessity for multi-step fabrication processes remain. This study demonstrates a novel approach for fabricating 3D structures by employing localized Joule heating on thermoset elastomers, aimed at enhancing the sensitivity of the soft pressure sensors. The thermal fields generated by localized Joule heating apply heat only to a designed area of the thermoset elastomer, enabling the formation of 3D structures in specific shapes. The localized Joule heating-induced 3D-structured film (LHSF) is utilized in a piezocapacitive soft pressure sensor. The sensor exhibits a high sensitivity of 1.352 kPa^-1 in the low-pressure range with a fast response time (0.59 s), excellent repeatability, and long-term stability. Finally, the advanced applicability of the proposed soft pressure sensors in diverse plans including grip pressure detection, motion monitoring, and multi-pixel pressure array pads is demonstrated.