Page 430 - AWSAR 2.0

406 || AWSAR Awarded Popular Science Stories - 2019
naturally existing species to develop artificial interfaces with the same property is termed as biomimicry. That’s the fabulous work Dr Manna is executing in his bio-inspired lab.’ My aunt was impressed while my brother was puzzled, both headed towards their own work while I began to surf through piles of research papers and review articles to learn the basics of superhydrophobicity, which finds extensive applications in oil/water remediation. As I dug deeper, it was disappointing to apprehend that the traditional methods used for cleanup and recovery of oil spills, that is in situ burning of oil, booms and skimmers, chemical dispersants and bio-remediation, had numerous limitations: (a) increased secondary pollution (air pollution); (b) was energy inefficient and time- consuming; and (c) was expensive. Moreover, the porous absorbents used lacked selectivity, that is, they ended up soaking both the oil and water, thus limiting their recyclability. Therefore, these glaring loopholes
paved the way for interfaces
with special wettability to be
efficiently applied for selectively
separating the oil phase while
repelling the water phase
because superhydrophobic
surfaces were inherently superoleophilic (oil absorbing).
‘Didi, dinner is served,’ my
brother exclaimed, breaking
my concentration. Three hours
just flew by. Curiosity overfilled
me and I googled Gulf of
Mexico Oil Spill, only to be left
astonished that the Macondo
oil well continued to leak crude
oil into the Gulf to date and the
threats faced by marine life
successfully brushed under
the carpet. As rightly quoted by Sir Jacques Cousteau ‘Water and Air, the two essential fluids on which all life depends, have become
global garbage cans’, the integration of industry and academia is the need of the hour to adequately address the matters plaguing life. Lost in thoughts, I was unusually quiet over dinner that night while my brother was happily narrating his playtime stories. Past dinner, my aunt knocked on my door, ‘How to fabricate bio-inspired interfaces?’ Thrilled with her curiosity, I sat down to explain, ‘The surface of the lotus leaf was extensively studied so as to artificially design a superhydrophobic interface. It was revealed that the surface of the leaf consisted of microstructures decorated with hydrophobic wax crystals imparting (a) nano features and (b) hydrophobic coating. These micro/nano features or rough structures collectively help to trap a metastable air layer, thus reducing the contact area between the surface and the water droplet. The hydrophobic coating further aids in repelling the water droplet completely. Therefore, to design a
bio-inspired superhydrophobic surface, the development of rough features on the surface and the hydrophobic coating are the essential requirements. Various superhydrophobic interfaces have been designed for applications in anti-icing coatings, drug delivery, textiles, optical devices and printing technologies, but their use in oil/water separation fascinated me. However, most of the superhydrophobic interfaces reported to date involve (a) tedious fabrication processes, (b) fragile chemistry, or (c) expensive and non- biodegradable chemicals, or (d) compromise the embedded
extreme water repellent property when subjected to severe physical abrasion tests or on exposure to harsh aqueous conditions,
‘When a water droplet falls on the lotus leaf, it tends to immediately roll off from the surface of the leaf, thus helping to keep the leaf dust free. This extreme water repellency is termed as superhydrophobicity and is the characteristic property of not just the lotus leaf but also taro leaf, rice leaf, butterfly wings and legs of the water striders that help them to float on the surface of the water.