Optimization of conductive elastomeric composites for directly printed intrinsically stretchable conductors


 Intrinsically stretchable solid-state conductors can shed light on the realization of further biocompatible and reliable wearable electronics. However, their material composition should be optimized considering the compatibility of target stretchable platforms. In this paper, we report directly printable conductive elastomeric composites for intrinsically stretchable conductors. Pneumatic direct ink writing (DIW) system is employed to deposit well-defined patterns. Polydimethylsiloxane (PDMS), Ag particles, and multi-walled carbon nanotubes (MWCNTs) were used as elastomeric matrix, conductive filers, and auxiliary fillers, respectively. Because there is a critical trade-off between the conductivity and stretchability depending on the concentration of conductive fillers, we optimize the Ag concentration to 77.5 wt% to fulfill these requirements. Especially, we introduce multi-solvent Ag composite inks to deliver excellent printability and enhanced conductivity simultaneously. We further investigate the electromechanical reliability of the encapsulated conductors undergoing cyclic strains, and they exhibited stable R/RO values over 50% strain.