Self-powered Wraparound (Abaxial) Droplet Deposition via a Superhydrophobic Surface Aid

Many diseases and pests are fond of the backs of leaves, making wraparound deposition essential for enhancing agrochemical utilization and minimizing environmental hazards. We present a superhydrophobic surface decorated with fluorinated-SiO2 nanoparticles on the adaxial (front) side, improving sprayed droplet wraparound behaviors and achieving a 10-fold increase in abaxial (backside) deposition without using an electrostatic sprayer. Solid-liquid contact electrification boosts the positive charge-to-mass ratio of rebound spraying from 17 to 454 nC g-1, with the abaxial surface acquiring opposite electric charges at kilovolt-level voltages. This intensified droplet-solid electrostatic attraction guides droplets to wrap around and deposit on the abaxial surface. Further, a homemade fluorinated superhydrophobic tube enhances spray charge and abaxial deposition density on superhydrophobic plant leaves by 47- and 5- times, respectively, compared to those obtained via direct spraying. This work will significantly improve agrochemical efficiency, reducing environmental risks in sustainable agriculture and related industries.