Steerable droplet precise bouncing on a superhydrophobic surface with superhydrophilic stripes

The precise rebound of a droplet upon hitting a solid surface has garnered significant attention in recent years due to its critical applications in self-cleaning, printing industries, and the design of heat exchanger surfaces, among others. This study introduces an innovative approach that combines femtosecond laser processing with a high-temperature stearic acid modification to create surfaces that feature superhydrophilic (SHL) stripes on a superhydrophobic substrate. By controlling the offset distance between the droplet's impact point and the SHL stripe, we achieved a directional and precise rebound of the droplets. Our findings indicate that the lateral displacement of the droplet increases with the offset distance and always tilts toward the direction of the SHL stripe. This study also incorporates numerical simulations to validate the findings, shedding light on the energy conversion mechanisms at the liquid–solid interface during the impact, particularly during the retraction phase. This discovery is significant for more accurately predicting the specific landing spots of rebounding droplets.