All-Liquid Metal Microparticles as Conductors, Solders, Vias Towards Stretchable Hybrid Electronics

The increasing demand for flexible hybrid electronics (FHE) has driven innovations in materials and fabrication methods to improve both efficiency and reliability. Among the challenges affecting reliability, repeated compression-induced failure is the major obstacle to scalable on-skin applications of FHE.
In this work, we present a novel approach using liquid metal microparticles (LMMPs) as conductors, solders, and vias to fabricate stretchable electronic circuits. LMMPs, ranging in diameter from 30 μm to 1 mm, are produced using a cryo-injection technique and selectively aligned to predefined circuit patterns. These LMP-connected circuits demonstrate stable conductivity under repeated tensile deformation, with resistance changes of less than 0.02 Ω after 1000 compression cycles at 150 kPa. The LMMPs-based circuits exhibit enhanced fatigue resistance compared to traditional gold wire connections, which fail under similar conditions. Additionally, we address the challenge of uncontrolled particle merging by utilizing a PSS acid layer, which stabilizes the LMPs and improves fabrication repeatability. Our method facilitates multilayer circuit production and offers a scalable solution for mass production of FHE, notably improving assembly speed with the use of a pick-and-place machine.