Thin Hydrogel–Elastomer Multilayer Encapsulation for Soft Electronics

Abstract

In the exciting race to design and engineer biointegrated and body-like electronic systems, many efforts concentrate on the integration of hydrogels in electronic assemblies. The versatility of hydrogels chemistry combined with their tissue-mimicking properties inspires numerous demonstrations of hydrogel-based touch panels, robots, and sensors over the years. However, their long-term integration in a thin and functional electronic assembly remains a challenge: their sensitivity to both air-drying and water swelling leads to important volume change of the network that is incompatible with the cohesion of a multilayer system, and has irreversible impact on the electronic properties of the assembly. To tackle this issue, proposed is a method to fabricate a hydrogel–elastomer micrometric bilayer with a stable interface, using of a low-swelling type of hydrogel, i.e., poly(2-hydroxyethyl methacrylate) and silicone rubber. The bilayer can sustain multiple hydration/dehydration cycles without delamination and can be kept for several months in its dry configuration. Combined with soft metallization technology, the bilayer can be readily integrated into a soft electronic circuit thereby opening a technological route for microfabricated, on-demand morphing systems.