Manipulating Droplet Dynamics for Enhancing Dropwise Condensation on the Ultra-Slippery Hydrophilic Surface

Ultraslippery hydrophilic (US-HI) surfaces with excellent droplet mobility are of great interest in science and engineering for various energy and water applications. Manipulating droplet dynamics and interactions on the US-HI surface can offer insights to enhance condensation heat transfer. In this work, a US-HI surface with an ultralow contact angle hysteresis is prepared by grafting PEG silane onto the substrate to minimize both the nucleation energy barrier and the sliding resistance of droplets for efficient dropwise condensation. Dynamic characteristics of condensed droplets on the US-HI surface are quantitatively investigated, including droplet growth, coalescence dynamics, contact line migration, and size distribution evolution. Compared with state-of-the-art condensing surfaces, the condensed droplets on the US-HI surface not only grow and coalesce about an order of magnitude faster but also detach and renew 24.8% more efficiently. The high-frequency droplet departure on the US-HI surface significantly increases the number density of microdroplets, which primarily contribute to dropwise condensation heat transfer, even surpassing the condensation rate observed on superhydrophobic surfaces. The findings offer insights and an avenue for droplet manipulation and surface design to achieve efficient phase-change processes.