High-Performance Capacitive Tactile Sensors Enabled by Self-Healing PDMS Networks with Enhanced Dielectric Properties via Cross-linking Density and Organic Salt Engineering

Abstract

The demand for flexible tactile sensors in wearable electronics and soft robotics has significantly increased, necessitating the development of dielectric materials that provide not only high performance but also long-term durability. Herein, we present a self-healing polydimethylsiloxane (PDMS) network engineered to improve dielectric properties through increased cross-linking density and the integration of an organic salt. In the polymer network, ester-functionalized cross-linkers serve as high-permittivity units, facilitating dipolar polarization and thus elevating the overall dielectric constant. To systematically evaluate the influence of cross-linking density, a range of cross-linkers with different numbers of ester groups was incorporated into the self-healing PDMS matrix. Despite the improvements, higher cross-linking density often results in increased stiffness, potentially compromising the flexibility of the material. To address this limitation, we incorporated the organic salt nickel(II) acetylacetonate (Ni(acac)₂), which substantially decreased the Young’s modulus and further promoted dielectric enhancement through the formation of an electric double layer. The optimized PDMS film, when implemented in a capacitive tactile sensor, demonstrated a rapid response time (<0.2 s), elevated sensitivity (0.1898 kPa^–1), and robust self-healing capability at 50 °C within 2 h, recovering up to 96% of its original electrical performance.