Smart Surfaces with Tunable Wettability

Abstract

Modification of surface wettability (ranging from complete wetting to complete non-wetting) of various surfaces is often required in many applications. Conventionally, it is done using a coating of suitable materials as per the requirement. In this approach, the old coating needs to be replaced every time by a new appropriate one. Alternatively, smart responsive surfaces can show tunable wettability with external stimulus. Electric field, temperature, light, pH, mechanical strain, etc. can be effectively used as external stimuli, and a suitable coating can be incorporated, which responses to the respective stimulus. These surfaces can be used to tune the surface wettability to any extent based on the magnitude of the stimulus. The primary role of the external stimulus is to vary the liquid-solid interfacial energy, which subsequently changes the surface wettability. The biggest advantage of this approach is that the surface wettability can be reversibly tuned. Each of the techniques mentioned above has many advantages along with certain limitations, and the combination of advantages and limitations helps users to choose the right technique for their work. Many recent studies have used this approach to quantify the tuning of the surface wettability and have also demonstrated its potential in various applications.

Hierarchical ‘rose-petal’ ZnO/Si surfaces with reversible wettability reaching complete water repellence without chemical modification

“…Wettability is an important surface property, essential for many applications and products, such as paints, advanced textiles, water repellency, dirt removal, oil-water separation, programmable liquid transport, anti-biofouling, and smart soft robotics, among others [1,2]. Furthermore, a surface with reversible wettability, switching between hydrophilicity and hydrophobicity, is required for rapid water motion, microfluidic devices, smart membranes, sensors, etc.…”