Superhydrophobic surfaces, which utilize a rough surface to trap a thin layer of air beneath a contacting fluid, can provide drag reduction, self-cleaning behavior, and condensation heat transfer enhancement. Meanwhile, lubricant infused surfaces, on which a lubricating oil is infused into a rough solid surface, are useful for many of the same applications, as well as reduction of biofouling. These technologies, however, exhibit limited durability: superhydrophobic surfaces physically and chemically degrade over time, and lubricant infused surfaces fail when their lubricating oil is depleted due to shear, evaporation, or cloaking of departing fluid droplets. We research methods to improve the durability of these two types of coatings, and also strive to develop entirely new methods for fluid repellency that don’t rely on surface coatings.
Related publications:
- Jumping Droplets Push the Boundaries of Condensation Heat Transfer
D.J. Preston, E.N. Wang
Joule, 2(2), 2018 - Heat Transfer Enhancement during Water and Hydrocarbon Condensation on Lubricant Infused Surfaces
D.J. Preston, Z. Lu, Y. Song, Y. Zhao, K.L. Wilke, D.S. Antao, M. Louis, E.N. Wang
Scientific Reports, 8(540), 2018
Fluid Wicking
Fluid wicking transports fluid by using capillary pressure, the same phenomenon that draws water up a thin glass tube until it eventually comes to rest. In porous media, liquid menisci pull fluid through the pores in an effort to minimize energy by covering the high-energy pore walls; if fluid is continuously removed from one end, though (as in an oil lamp’s wick, or in a heat pipe as liquid evaporates at the hot end), the fluid flow is continuous. We optimize wicking materials by altering their porosity, permeability, wettability, and other parameters, thereby tailoring wicking materials for given applications.
Related publications:
- Gravitationally-Driven Wicking for Enhanced Condensation Heat Transfer
D.J. Preston, K.L. Wilke, Z. Lu, S.S. Cruz, Y. Zhao, L.L. Becerra, E.N. Wang
Langmuir, 34(15), 2018 - Porous Cu Nanowire Aerosponges from One-Step Assembly and their Applications in Heat Dissipation
S.M. Jung, D.J. Preston, H.Y. Jung, Z. Deng, E.N. Wang, J. Kong
Advanced Materials, 28(7), 2015
Fluid Manipulation
Active, dynamic control of fluids can generate unique behaviors that both elucidate fundamental physical concepts – as we have done with ejection of droplets from surfaces, by electrowetting, to study the conversion of surface energy to kinetic energy – and solve real-world problems – demonstrated by our electrowetting-actuated stage to eliminate stiction in microelectromechanical devices. We continue to pursue both a deeper understanding of fundamental fluid behavior and the translation of this understanding to solutions for relevant problems.
Related publications:
- Electrowetting-on-Dielectric Actuation of a Vertical Translation and Angular Manipulation Stage
D.J. Preston, A. Anders, B. Barabadi, E. Tio, Y. Zhu, D.A. Dai, E.N. Wang
Applied Physics Letters, 109(24), 2016 - Electrically Induced Drop Detachment and Ejection
A. Cavalli, D.J. Preston, E. Tio, D.W. Martin, N. Miljkovic, E.N. Wang, F. Blanchette, J.W.M. Bush
Physics of Fluids, 28(022101), 2016