Affiliation: University of Michigan
Hosted By: Professor Bharat Bhushan
Description: In this talk I will discuss the current work in my group on developing surfaces with extreme wettabilities, i.e. surfaces that are either completely wet by, or completely repel, different liquids. The first portion of the talk will cover the design of so called “superomniphobic surfaces” i.e. surfaces which repel all liquids. Designing and producing textured surfaces that can resist wetting by low surface tension liquids such as various oils or alcohols has been a significant challenge in materials science, and no examples of such surfaces exist in nature. As part of this work, I explain how re-entrant surface curvature, in addition to surface chemistry and roughness, can be used to design surfaces that cause virtually all liquids, including oils, alcohols, water, concentrated organic and inorganic acids, bases, solvents, as well as, viscoelastic polymer solutions to roll-off and bounce.
The second portion of my talk will cover the design of the first-ever reconfigurable membranes that, counter-intuitively, are both superhydrophilic (i.e., water contact angles @ 0°) and superoleophobic (i.e., oil contact angles > 150°). This makes these porous surfaces ideal for gravity-based separation of oil and water as they allow the higher density liquid (water) to flow through while retaining the lower density liquid (oil). These fouling-resistant membranes can separate, for the first time, a range of different oil–water mixtures, including emulsions, in a single-unit operation, with >99.9% separation efficiency, by using the difference in capillary forces acting on the oil and water phases. As the separation methodology is solely gravity-driven, it is expected to be one of the most energy-efficient technologies for oil-water separation.
I will also discuss surfaces with patterned wettability, where both wetting (omniphilic) and non-wetting (omniphobic) domains are fabricated on the same substrate. We use such substrates for fabricating monodisperse, multi-phasic, micro- and nano-particles possessing virtually any desired composition, projected shape, modulus, and dimensions as small as 25 nm. Finally, I will discuss some other areas of current and future research, including the development of ice-phobic coatings that offer one of the lowest reported adhesion strengths with ice.
Affiliation: GE Aviation, Cincinnati, OH
Hosted by: Professor Marcelo Dapino
Affiliation: University of Virginia
Hosted by: Professor Bharat Bhushan
Recent discoveries in seashells unveil that nature uses multiscale design strategies to achieve exceptional mechanical properties which are still beyond the reach of many engineering materials. The multiscale hierarchical structure, ranging from micro lamellae down to nanoparticles, renders seashells multilevel strengthening and toughening mechanisms such as crack deflection, interlocking, lamellae’s deformability, biopolymer’s viscosity, nanoparticle rotation, deformation twining in nanoparticles, and amorphization, jointly contributing to seashell’s ultra-high mechanical robustness. To realize nature’s performance in engineering materials, we need to intelligently design and select materials. This talk will present several case studies in which nature’s multiscale design strategies and materials selection principles are applied through additive manufacturing.
About the Speaker
Xiaodong (Chris) Li is a Rolls-Royce Commonwealth Professor and the graduate director in the Department of Mechanical and Aerospace Engineering at the University of Virginia. He is an ASME Fellow and a SEM Fellow. His research expertise and interests include (but not limited to) biological and bio-inspired materials, biomechanics, biomass-derived energy storage, nanomechanics, surface engineering, and tribology. He has published over 230 peer-reviewed journal articles including Science, Nature Communications, Advanced Materials, Nano Letters, Physical Review Letters, Acta Materialia, Acta Biomaterialia, Physical Review B, and Journal of the Mechanics and Physics of Solids. His publications have been cited over 10,580 times with H-index of 50. He has received several awards including the TMS MPMD Distinguished Scientist/Engineer Award (2015) and the Professional Engineering Publisher´s PE Prize (2008). His breakthrough work has been featured by Science Daily, Discovery News, BBC, and MSNBC. His innovation was selected by New York Times – Year in Ideas for Year 2010. He is an associate editor for Transactions of the ASME – Applied Mechanics Reviews and serves on editorial board for ten journals. He was the elected chair for TMS nanomechanical materials behavior committee.