Steerable Droplet Bouncing for Precise Materials Transportation

Directional transportation of liquid droplets plays a significant role in various processes including anti-fogging, anti-icing, and materials transportation. Diverse strategies have been developed to achieve lateral bouncing of impacting droplets. However, due to the complexity of the interactions on the interface between a droplet and the solid, quantitatively manipulating the directional movement of the droplet still remains challenging. Here, it is proposed that the directional transportation of a droplet with precise controllability can be achieved by impacting it on a heterogenously wettable surface. It is found that the droplet lateral momentum correlates with the surface area of a geometric region that depends on the position-coupling between the droplet maximum spreading and the wettability pattern. The well-controlled droplet directional movement has generality for different Weber numbers and diverse superhydrophilic patterns. Based on this principle, functional materials are orientated to achieve precise positioning of regents for demand-on chemical reactions, and micro-floats are driven with different moving velocities. It offers a promising strategy for accurate droplet manipulation based on patterned wettability, which shows great potential in applications such as functional materials transportation, microfluidics, and energy collection and utilization.