High Resolution Soft and Stretchable Circuits with PVA/Liquid‐Metal Mediated Printing

Abstract

AbstractA novel technique that permits, for the first time, fabrication of stretchable traces with linewidths as low as 20 µm and line‐spacing of 30 µm, based on simple coating and printing techniques, performed entirely at ambient condition, is demonstrated. By relying on existing inkjet printing technique, the proposed sinter‐free method is a step toward scalable fabrication of high‐resolution stretchable circuits, with application in logic gates, transparent conductors, and solar panels. This is accomplished by coating a layer of poly(vinyl alcohol) (PVA) over an elastic substrate, inkjet printing a circuit with silver nanoparticle (AgNP) ink, and then coating the printed circuit with a thin film of eutectic gallium‐indium‐tin (Galinstan) alloy. The Galinstan coating selectively wets to the printed AgNPs, resulting in highly conductive (6.65 × 106 S m−1) circuits that can withstand over 100% of strain with a modest gauge factor of ≈2.7. The process does not need thermal sintering, thanks to the Galinstan fusion with AgNPs, thus being compatible with heat‐sensitive substrates. The PVA coating has a critical role as a hydrophilic surface that absorbs the water‐based ink but resists wetting of the Galinstan. This method is demonstrated over a variety of substrates, including ultrasoft polyurethanes, ultra‐stretchable styrene–ethylene/butylynestyrene, and polyimide.