Sandwiched Polyethylene Shrink Film Masking with Tunable Resolution and Shape for Liquid Alloy Patterning

Among numerous patterning techniques, masked liquid alloy printing is one of the most promising techniques for scalable fabrication of liquid-alloy-based stretchable electronics. Like any other mask-based process, its resolution is often constrained by the quality of the mask, and the fabrication cost increases drastically with increased resolution. In this work, by introducing a sandwiched thermal shrink polymer film masking technique and a corresponding intermediate release agent, fine liquid alloy patterns were demonstrated by using a mechanical cutting plotter together with a common oven. The final resolution and shape of the mask could be tuned based on the anisotropy of the shrink polymer film and other operational parameters of the technique. After shrinkage, the width of the patterned liquid alloy lines and space in-between could be tuned to less than one third of the original cut pattern, to about 35 and 60 mu m, respectively, according to requirements. To better predict the final structure, several parameters were investigated experimentally and numerically. Finally, a liquid alloy strain sensor and three-dimensional conformal masking were demonstrated, showing the potential of the developed technique.