Ideally, liquid repellents would have a structure that supports robust liquid repellency and strong mechanical stability, while being inexpensive enough to produce commercially. So far, those outcomes have not been satisfactorily achieved. However, a recent breakthrough in research led by Professor Wang Liqiu at the department of mechanical engineering at the University of Hong Kong (HKU), has resulted in a promising solution in the form of an innovative microfluidic-droplet-based technique.

Soil-dwelling springtails with dew (body length: ~2.5 mm). Image credit: Brian Valentine Flickr.comUsing a design inspired by springtails, soil-dwelling arthropods, the team effectively resolved the conflict between liquid-repellency and mechanical stability. The springtails habitat is often impacted by rain and flooding, and as a consequence, their cuticles exhibit both strong mechanical durability to resist friction from soil particles and exceptional liquid repellency to survive in watery environments. The research team designed porous surfaces composed of interconnected honeycomb-like micro-cavities with a re-entrant profile -- interconnectivity ensures mechanical stability and re-entrant structure yields robust liquid-repellency.

Liquid-repellent surfaces serve an important purpose in a number of applications such as water-repellent clothing. Used as drag-reduction coating for water vehicles, they can save energy by improving the speed of cargo ships and military equipment.

Watch a demonstration here.

The paper was recently published in the academic journal Nature Communications.