Strain-Dependent Dielectric Properties of Liquid Metal Polymer Composites for Stretchable Electronics

Dielectric materials used in soft electronics must withstand mechanical strain without compromising electrical reliability, which introduces a challenge for current systems, where deformation can trigger premature failure. Liquid metal polymer composites (LMPCs) offer a promising solution by combining the high conductivity of galinstan with the intrinsic deformability of silicone-based elastomers. Although LMPCs have been widely studied for their strain-dependent conductivity and static mechanical behavior, their dielectric insulation performance under mechanical strain remains poorly understood. Most prior studies assume constant dielectric behavior, which overlooks the influence of deformation on the internal structure and polarization mechanisms. In applications where materials are routinely deformed, understanding how deformation affects the dielectric behavior is essential. LMPCs were fabricated by dispersing galinstan droplets within polydimethylsiloxane (PDMS) matrices to produce three distinct droplet sizes and were then subsequently diluted to targeted concentrations. This study investigates the effect of tensile strain on key dielectric properties, including permittivity, dissipation factor, dielectric strength, and partial discharge inception electric field (PDIE). Results show that the dielectric behavior of LMPCs is highly strain-dependent. Under increasing strain, LMPCs exhibit a decrease in permittivity, accompanied by an increase in dielectric strength and PDIE. Additionally, composites with larger droplets initially display higher permittivity due to enhanced interfacial polarization but suffer from lower dielectric strength, revealing a key trade-off between dielectric performance and electrical durability. These findings provide valuable insight into the strain-sensitive dielectric response of LMPCs for high-voltage, stretchable electronic systems.