Process and property assessment of liquid metal spray deposition towards scalable and reliable stretchable electronics

Abstract

Liquid metal stretchable electronics combine exceptional softness, stretchability, and self-healing capabilities, making them ideal for smart wearables and soft robotics. A key fabrication approach involves pneumatic spray deposition into patterned structures. However, the impact of process parameters on LM deposition remains poorly understood, largely due to reliance on manual airbrushing-limiting both scalability and reliability. This work addresses these challenges with a custom-built automated spray coater, offering precise control over key parameters such as flow rate, pressure, and spray distance. Through systematic process-property analysis, we reveal that rougher coatings improve device yield (approaching 100%) but compromise long-term reliability. Finer linewidths (0.25 mm) fail earlier in cyclic testing and exhibit reduced self-healing compared to wider lines (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\ge$$\end{document} 0.5 mm). Scalability is demonstrated through the fabrication of a large-area wearable strain sensor (70 \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\times$$\end{document} 150 mm) for human motion capture. These findings offer critical insights into process-structure-property relationships, paving the way for reliable, scalable LM-based stretchable electronics.