I-wi: Multifunctional 3D-printable stretchable ionogel and ionic eutectogel wires with AC and DC signal transmission

Abstract

Recent advances in technologies based on soft matter functionality have spurred the demand for flexible and stretchable conductors. However, state-of-the-art stretchable conductors suffer from trade-offs between material compositions, design and scale factors, electrical properties, durability, and precise fabrication methods, thus sacrificing critical parameters and hindering performance. The longstanding challenge in the field has been co-developing reliable, stretchable, and highly electrically conductive bulk elastomers with precise fabrication methods for transferring diverse signals over distances, while both at rest and in a stretched state under both DC and AC conditions. In this study, we developed, characterized, and showcased i-wi (ionic wires) — soft, stretchable, and 3D-printable ionogels and ionic eutectogels designed for applications in soft stretchable electronics under both DC and AC. We combined imidazolium-based ionic liquids (ILs) or ethaline and glyceline deep eutectic solvents (DESs) with photopolymer compositions to obtain ionogels or eutectogels, respectively, that combine elastic deformation with high ionic conductivity and that can be precisely 3D-printed using the vat photopolymerization method. We showed that i-wi can transfer both DC and AC signals in various implementation scenarios, extending the horizon for myriad applications. We demonstrated the multifunctionality of i-wi in multimaterial connectors, which conducted signals to light LEDs, play music, and perform electric guitar, while both at rest and under stretching, and which functioned as precise temperature and strain sensors. We suggest that i-wi may become a core component of physically intelligent systems, including morphological computing, advanced wearable and medical devices, and the broader field of soft robotic systems.