A Dynamically Responsive Surface with Switchable Wettability for Efficient Evaporation and Self-Cleaning Abilities

Evaporation is crucial in applications such as nanoscale fabrication, inkjet printing, heat transfer, and self-cleaning electronics. This study demonstrates a switchable surface that dynamically transitions between superhydrophobic and superhydrophilic states. Superhydrophobic surfaces are renowned for their intrinsic self-cleaning properties and notably sluggish evaporation kinetics. On the other hand, superhydrophilic surfaces exhibit rapid evaporation kinetics and induce evaporative cooling effects, making them advantageous for heat dissipation and cooling applications. This study proposes a switchable surface that seamlessly shifts between these two states based on external stimuli.<br/>To facilitate the understanding of this switchable surface, the study employs a self-cleaning superhydrophobic aluminum substrate coated with an amino-silane (N-(2-aminoethyl)-11-aminoundecyl-trimethoxysilane). Typical nonwetting coatings, such as lauric acid and FDTS (perfluorodecyltrichlorosilane) are also compared in terms of wettability and evaporation kinetics. During periods of low heat loads, the surface capitalizes on the self-cleaning nature of superhydrophobicity, reducing energy waste and minimizing maintenance needs. Conversely, when subjected to high heat loads, the dynamic transition to a superhydrophilic state facilitates rapid evaporation, thus unlocking effective evaporative cooling effects. By combining these dual characteristics, the proposed surface transcends conventional boundaries, offering multifaceted benefits. The experimental concept is underscored by an in-depth analysis of evaporation rates using both calorimetry and contact angle goniometry. Addressing the complexities arising from superwetting surfaces, which challenge the precise determination of droplet boundaries, this research predicts evaporation rate of both wetting and nonwetting surfaces.