Wetting behavior of a water droplet on a mutual periodic micro-patterned ternary texture structure

Abstract

Wetting behavior of a water droplet at a hydrophilic ternary texture structured (TTS) surface is unclear and rarely reported. Herein, wetting behavior of a water droplet was examined for the first time at a micro-patterned hydrophilic TTS-based moisture sensor chip (TTS@MSC) composed of confined silica gap between gold and aluminum arrays. Macroscopic and microscopic behaviors of water droplet were examined using contact angle measurement and reflection interference contrast microscopy (RICM), respectively. Experimental results revealed that water droplet exhibits Cassie state when it was observed parallel (║) to arrays due to existence of air pocket between water droplet and TTS@MSC surface. Moreover, parallel (║) observation to arrays indicated better adhesion stability of water droplet over perpendicular (┴) observation due to existence of arrays that restricted droplet free motion. In addition, volume-based experimental scheme revealed that water droplet loses its adhesion with TTS@MSC surface once its volume exceeds 10 μL. These findings suggested that tiny volume water droplets possess strong contact and adhesion stability at TTS@MSC surface which can feasibly enhance their accurate quantitative and qualitative detection in real practical fields. Present study is believed to open the door for a comprehensive understanding of the wetting behavior at numerous TTS surfaces for various water harvesting and/or repelling-based applications.