Abstract: Traditionally, omniphobic surfaces were fabricated mainly by mimicking Lotus leaves, Shark skin, bird feathers, flower petals [1]. Those surfaces are vulnerable to mechanical damage and suffered from wear-sensitivity due to apolar coatings/substrates and protruding roughness elements. This led to the loss of superhydrophobic and oleophobic properties post abrasion. Therefore, dewetting and wear-resistance properties were at odds with each other and fabricating highly wear-resistant liquid-repellent surfaces was an open challenge in the wetting community. Nevertheless, in my Ph.D. thesis, by bio-mimicking a carnivorous Nepenthes Pitcher plant’s strategy to catch its prey, the lubricant impregnated mesoporous alumina composites were fabricated [2] and are commonly referred to as slippery liquid impregnated porous surfaces (SLIPS) [3]. The hard Al2O3 matrix provides high wear-resistance while the lubricant (perfluoropolyether) aids in the dewetting slippery properties towards other immiscible liquids and suspensions namely water, alkanes and acrylic paints. A scheme showing the slippery nature of water drop atop Fomblin® oil impregnated mesoporous Al2O3 and a tribo-counter body are presented in Fig. 1. Low friction coefficients of 0.025, high wear-coefficients of 10-8 mm.N-1.m-1, extremely high load-bearing capacities of 300 MPa (three orders of magnitude higher than conventional omniphobic surfaces) were obtained [4]. The capillary and surface diffusion processes of the lubricant enable self-healing by these composites post harsh abrasion, wherein, the surface diffusion was found to be the rate determining mechanism. A dewetting-tribology diagram has been introduced for the first time to show different regimes, namely—optimal slippery properties, optimal tribological properties, and a mixed regime [5]. Such abrasion-resistant slippery surfaces may potentially find applications in paint industries, as anti-icing surfaces and in medicine.
Bio: Sriharitha Rowthu is primarily a materials researcher and interested in synthesizing, characterizing and tuning the functional interfaces for wetting and tribological applications. Her education in integrated dual degree program at Indian Institute of Technology (IIT) Madras during 2006-2011 in Metallurgical and Materials Engineering department gave an overview of materials characterizations for correlating their microstructure with physicochemical, thermal and mechanical properties. Following that, during her Ph.D. education (2011-2016) at École polytechnique fédérale de Lausanne (EPFL) and jointly at Empa Thun, Switzerland, she had an opportunity to dive into non-wettable surfaces. Nature inspired strategies by mimicking Lotus leaf, and Nepenthes Pitcher plant were explored and adapted to many polymers, their composites and intriguing Al2O3 ceramics. In addition, she had investigated the tribological properties of lubricant infused alumina as well as manufactured surface micro and nanopatterns via soft lithography techniques. She has been highly interested in applying simple analytical models in the domain of liquid transport phenomena for predicting the drying time of slurry during colloidal lithography and self-healing time of SLIPS post harsh abrasion. She is presently investigating the catalytic properties of Pt nanoparticles deposited on structural components of boiling water reactors as a postdoctoral researcher in the Laboratory for Nuclear Materials at Paul Scherrer Institute (PSI) in Switzerland. So far, Sriharitha Rowthu has supervised two masters’ students and published a total of 9 articles as well as one invited book chapter. She has envisioned and served as the principal investigator of two highly ranked synchrotron proposals for using XRF for obtaining large area high resolution spatial mapping of Pt nanoparticles. In the future, she wishes to continue researching and pursue teaching in the fields of wetting, colloidal processing, transport phenomena and tribology.