Condensations on electrowetting surfaces: An electrostatic liquid conveyor from dropwise-filmwise competition

• Published in: International journal of heat and mass transfer Vol. 213; p. 124280
• Main Authors: Pham, Robin, Yan, Run, Wang, Sheng, Chen, Chung-Lung
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.10.2023
• Subjects: Condensation; Dropwise; Electrowetting; Filmwise; Liquid conveyor; Thermal efficiency; Electrowetting; Dropwise; Filmwise; Thermal efficiency; Condensation; Liquid conveyor
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2023.124280

•A sandwiched electrode electrowetting isolates different stages of the condensation growth.•Electrostatic conveyor system occurs from dynamic wettability and mass imbalances.•Tuning of timescales controls the migration direction of condensed droplets.•37–49% enhancement arises from size regulations of the droplet population.•Enhancement from nucleation increases parabolically with voltage, >150% at the material limit. In contrast to the traditional point of view, electrowetting creates a dynamic wetting regime. Hydrophilicity can penetrate or recede from the working surface –depending on the liquid locale rather than the substrate structures. Size regulation forms droplet clusters as condensation accumulates. Coalescence cascades and mass imbalances transfer the liquid from one zone to the next. What ensues is a passive electrostatic liquid conveyor that takes the condensation away from its constant self-stagnating cycles. Each working zone functions independently from one another according to its intended purpose: nucleation and diffusion, accumulation and collection. 40 to 50 percent of the increase in liquid recovery traces its root to the spatial-size regulation of the droplet population. Simultaneously, the gain from higher nucleations runs parabolically with electrostatic voltage. The competition between dropwise and filmwise tendencies determines the migration of condensates. Yet, the autonomy of the two means that nucleations are direct and unhindered as to how high an electrostatic voltage can be: the only limit is the material strength and endurance to sustain this concentration of electric potentials.