Superhydrophobic self-cleaning surface derived from rice-husk ash

In a present work, scientists report the development of durable and cost-effective nanocomposite coatings using silica particles derived from agricultural waste, rice-husk and different fractions of polydimethylsiloxane (PDMS).

Brown stems with elongated grains
Surface with inherent self-cleaning characteristics is often deemed and desired. However -

Developed coatings showed the presence of hierarchical structures with nanoscale protrusions. The surface morphology of the coatings was significantly influenced by the PDMS content with roughness factor following an inverse correlation. Static and dynamic contact angles increased with decreasing PDMS content with maximum values observed to be in excess of 160°. Simultaneously, the contact angle hysteresis (< 5° to 20°) and tilting angle (5° to 60°) were also significantly influenced by the PDMS fraction. The observed results are related with ability to retain stable Cassie state and pinning of the liquid-air interface by nano protrusions.

Due resilience under outdoor conditions

Droplet impingement tests and critical wetting angle calculations showed transition from Cassie to metastable wetting state for coatings with higher PDMS. Durability studies performed under different modes indicated a trade-off with self-cleaning ability, highlighting an optimum composition possessing required characteristics. The selected coating subjected to weathering test showed due resilience under outdoor conditions. The present work showed that the agricultural waste can be effectively used for developing low-cost high-end product possessing exceptional functionalities.

The study is published in: Progress in Organic Coatings Volume 136, November 2019, 105221.

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