Large-area photo-patterning of initially conductive EGaIn particle-assembled film for soft electronics

Eutectic-gallium-indium particle (EGaIn*) is considered one of the promising conducting materials for soft electronics due to its enhanced stability compare to bulk EGaIn and constant conductance under strain. However, its practical implementation has thus far been limited due to the challenges of achieving initial electrical conductivity and the incompatibility with well-developed fabrication strategies. Here, we report materials and manufacturing methods that allow large-area multi-layered patterning of ‘polystyrene sulfonate (PSS)-attached EGaIn* (EGaIn*:PSS)’ thin-film with the conventional cleanroom process. PSS enhances the stability of EGaIn*, which allow uniform thin-film coating and photographic lift-off at a wafer-scale down to 10 μm features of varying thicknesses. Using dimethyl sulfoxide as the solvent during lift-off induces cohesion between EGaIn*:PSS, resulting in initial electrical conductivity without an additional activation process. Demonstrations of stretchable display, multilayer pressure sensing systems, and soft artificial finger validate the versatility and reliability of this manufacturing strategy for soft electronics.