Spontaneous droplets gyrating via asymmetric self-splitting on heterogeneous surfaces

Droplet impacting and bouncing off solid surface plays a vital role in various biological/physiological processes and engineering applications. However, due to a lack of accurate control of force transmission, the maneuver of the droplet movement and energy conversion is rather primitive. Here we show that the translational motion of an impacting droplet can be converted to gyration, with a maximum rotational speed exceeding 7300 revolutions per minute, through heterogeneous surface wettability regulation. The gyration behavior is enabled by the synergetic effect of the asymmetric pinning forces originated from surface heterogeneity and the excess surface energy of the spreading droplet after impact. The findings open a promising avenue for delicate control of liquid motion as well as actuating of solids. Controlling droplet impact and rebound behaviour can have applications in inkjet printing and self-cleaning. Here the authors show how a chemically-patterned surface with high-adhesive spirals surrounded by hydrophobic, low-adhesive regions leads to gyration behaviour of impacting droplets.