Study on the Motion Behavior of Charged Droplets near Plant Leaves

Conventional spraying often results in poor deposition on the abaxial (lower) leaf surface and within the middle-to-lower canopy, where pest and disease pressures are typically highest. In this study, we evaluated the performance of electrostatic spraying using basil (Ocimum basilicum), cucumber (Cucumis sativus), and chili pepper (Capsicum annuum) leaves as target surfaces. A high-speed imaging system was employed to map droplet distributions on the abaxial surface, while a neighborhood-matching algorithm combined with droplet tracking was used to quantify the motion of individual droplets near the leaf. At the steady-state stage (frame 4500, 2.25 s), the number of charged droplets detected beneath the abaxial surface increased by 112% (basil), 132% (cucumber), and 213% (chili pepper) compared with non-electrostatic spraying. Smaller charged droplets exhibited higher horizontal velocities and smaller deflection angles in their trajectories near the leaf, indicating a stronger tendency to migrate toward the target surface and into the canopy interior. These findings demonstrate that electrostatic forces substantially enhance abaxial deposition and provide practical guidance for optimizing parameters for electrostatic spraying, such as droplet size, to improve spray efficiency in agricultural applications.