Scalable Electrodeposition of Liquid Metal from An Acetonitrile-Based Electrolyte for Highly-Integrated Stretchable Electronics.

The advancement of highly-integrated stretchable electronics requires the development of scalable (sub)-micrometer conductor patterning. Eutectic gallium indium (EGaIn) is an attractive conductor for stretchable electronics, as its liquid metallic character grants it high electrical conductivity upon deformation. However, its high surface energy makes its patterning with sub-micron resolution challenging. Herein, we overcome this limitation by reporting for the first time the electrodeposition of EGaIn. We use a non-aqueous acetonitrile-based electrolyte that exhibits high electrochemical stability and chemical orthogonality. The electrodeposited material led to low-resistance lines that remained stable upon (repeated) stretching to a 100% strain. Because electrodeposition benefits from the resolution of mature nanofabrication methods used to pattern the base metal, the proposed "bottom-up" approach achieved a record-high density integration of EGaIn regular lines of 300 nm half-pitch on an elastomer substrate by plating on a gold seed layer pre-patterned by nanoimprinting. Moreover, vertical integration was enabled by filling high aspect ratio vias. This capability was conceptualized by the fabrication of an omnidirectionally stretchable 3D electronic circuit, and demonstrates a soft-electronic analogue of the stablished damascene process used to fabricate microchip interconnects. Overall, this work proposes a simple route to address the challenge of metallization in highly-integrated (3D) stretchable electronics. This article is protected by copyright. All rights reserved.