This review article exemplifies the importance of self-cleaning materials and coatings. Selfcleaning coatings are becoming an integral part of our daily life because of their utility in various applications such as windows, solar panels, cements, paints, etc. In this review, various categories of materials for the fabrication of hydrophilic, hydrophobic, oleophobic, amphiphobic and multifunctional coatings and their synthesis routes have been discussed. Furthermore, different natural organisms exhibiting superhydrophobic behaviour have been analysed. This review also covers the fundamentals of self-cleaning attributes such as water contact angle, surface energy, contact angle hysteresis, etc. Fig. 1 Pictures of water droplets on Lotus (left) and Ramee (right) leaf indicating the self-cleaning property inherent in nature. 1 Inset of a: pictures of water droplet on Lotus (left) and Ramee leaf (right) indicating their inherent selfcleaning nature.

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Cellulose Nanocrystals (CNC) are explored to stabilize oil/water emulsions for their ability to adsorb at the oil/water interface. In this work, the role of electrostatic forces in the CNC ability to stabilize oil/water emulsions is explored using canola oil/water and hexadecane/water as model systems. Canola oil/water and Hexadecane/ water (20/80, v/v) emulsions were stabilized with the addition of CNCs using ultrasonication. Emulsion droplet sizes range from 1 to 4 μm as measured by optical microscopy. It is found that CNC can stabilize oil/water emulsions regardless of their charge density. However, reducing the surface charge density, by adding salts and varying pH, can reduce the amount of CNC's required to form a stable emulsion. Just by adding 3 mM Na+ or 1 mM or less Ca+2 to a CNC suspension, the amount of CNC reduced by 30% to stabilized 2 mL of Canola oil. On the other hand, adding salt increases the emulsion volume. The addition of 100 mM Na+ or the reduction of pH below 2 leads to the aggregation of CNC; emulsions formed under these conditions showed gel-like behavior. This work shows the potential of nanocellulose crystal in stabilizing food and industrial emulsions. This is of interest for applications where biodegradability, biocompatibility, and food grade requirements are needed.

Cellulose nanocrystals (CNCs) are a particularly appealing format of the natural biopolymer due to their exceptional strength, nanoscale dimensions, and needle-like shape anisotropy. However, CNCs are hydrophilic and hence their wettability makes them impractical for many coating applications, with various approaches using chemical functionalization to overcome this. Here we show that CNC-coated surfaces can be rendered hydrophobic by alignment of the native CNCs using a wrinkled template-mediated printing process. We present a novel and simple method allowing full release of the CNCs from the template and their permanent adsorption into fine patterns onto the surface, thus preventing CNC repositioning during wetting. The aligned CNCs induce strong pinning effects that capture and retain water droplets with high contact angle and large roll-off angles, without becoming susceptible to oil contamination. The fabrication process for these coatings could be achieved by large-scale printing, making them a practical and cost-effective solution to hydrophobic coatings from raw cellulosic materials.