Pinhole formation from liquid metal microdroplets impact on solid surfaces

摘要

The impact of molten metal droplets on solid substrates may entrap gas to form pinholes. This letter shows that the detailed pinhole structure is more sophisticated than expected: the void is toroid, which is a result of rapid contact line retraction and subsequent phase change. The substrate surface roughness affects the pinhole size by providing leaky channels that weaken gas pressure buildup. When the droplet diameter is sufficiently large, Kevin-Helmholtz instability may be triggered to form multiple pinholes.