Fabrication of a Flexible Strain Sensor with High‐Aspect‐Ratio Liquid‐Metal Galinstan

Abstract Flexible electronic devices containing gallium‐based liquid metal (GbLM) play an important role in human–computer interaction and the sensing elements of motion monitoring owing to the intrinsic fluidity and metallic conductivity of the GbLM. High‐aspect‐ratio liquid‐metal patterns have 3D structures, which can increase the heat radiating area of the circuits and the stability of the sensors. However, fabricating high‐aspect‐ratio patterns in high resolution is challenging owing to easy oxidation at the surface layer and the high surface tension of the liquid metal. This study proposes a simple method for the efficient and reproducible fabrication of GbLM patterns. A flexible strain sensor was obtained with high‐aspect‐ratio Galinstan (height/width > 5), linearity (R‐square = 0.9975), stability (ΔR/R₀ < 0.8 after 10 000 cycles), and low hysteresis. In addition, the application of the strain sensor in the flexible display and motion measurement of soft hand exoskeletons is demonstrated. The high‐aspect‐ratio liquid‐metal patterns in this work have the potential to extend the application of the presented flexible electronics to the fields of wearable systems and rehabilitation devices.