Fully screen printed stretchable liquid metal multilayer circuits using green solvents and scalable water-spray sintering

Abstract

Stretchable circuits based on liquid metals are promising for wearables but the lack of scalable processes for sintering of printed liquid metal dispersions constitutes a challenge for large-area and high-volume manufacturing. In this work, materials and methods for fully screen printed stretchable liquid metal multilayer circuits have been developed. The ink is based on liquid metal droplets dispersed in the green solvent propylene glycol using the harmless dispersion agent polyvinylpyrrolidone. The development of a scalable water-spray sintering method in combination with ink optimization yielded highly conductive prints of ≈7.3 × 10⁵S/m. Interestingly, the printed conductors experienced a resistance increase of less than 10% during 50% strain cycling, which is far below the expected 125% increase due to the geometry factor. The process allows for printing of high-performance multilayer circuits, which is demonstrated by the development of printed stretchable near-field communication tags.