(603b) Liquid Metal Multi-Material Dielectric Composites for Multimodal, Deformable Capacitive Pressure Sensing

Deformable dielectric composites for capacitive pressure sensing are a promising alternative to traditional rigid dielectric materials. In particular, deformable dielectrics have the potential to enhance device sensitivity/responsiveness, increase human−machine interface biocompatibility and conformability, and improve material durability. To advance dielectric composites for pressure sensing, soft robotics, and stretchable electronics, this work utilizes the room-temperature liquid metal galinstan, a gallium-indium-tin alloy, as liquid metal offers the combination of both metallic conductivity and intrinsic liquid deformability. Dispersing galinstan into elastomers creates dielectric composites that possess tunable mechanical and electrical behavior, including modulus and relative permittivity. Prior work has shown that these dielectric elastomer composites have minimal impact on bulk modulus while concurrently achieving remarkable permittivity. While promising, galinstan composites tend to be costly and have challenges associated with decreased electrical and mechanical material reliability (i.e., dielectric aging). To address these barriers to implementation, this work investigates novel multi-material dielectric composites that combine galinstan and a rigid filler, either iron (conductive) or barium titanate (dielectric) to develop tunable design parameters, including fabrication method, morphology, mechanical deformation, dielectric behavior, and capacitive pressure sensing performance. These multi-material composites were found to have highly responsive sensing behaviors, which depended on material modulus and permittivity leading to improved sensitivity and linearity. Through developing tunable material behaviors, a balance between superior electric performance and lower modulus can be precisely calibrated for specific user needs in deformable capacitive pressure sensing applications that will advance current abilities of deformable dielectric materials.