Counterintuitive Pancake Bouncing Phenomenon on Superhydrophobic Surfaces: From Fundamental Understanding to Anti-icing Application

Preventing the formation/accumulation of ice on solid surfaces as well as promoting its easy detachment without energy input is of importance for a wide range of applications including in transportation, energy system, telecommunications and aerospace. The state of the art active ice mitigation approaches require substantial energy input and pose detrimental environmental impacts. Alternatively, passive approaches leveraging the surface wettability for anti-icing offer tremendous promises. Particularly, inspirations from natural nonwetting structures such as lotus leaves have accelerated the development of various superhydrophobic surfaces that enable fast detachment of drops before they are frozen.Recently, we discovered a very exciting and counterintuitive drop impact regime on a novel superhydrophobic surface with special textures. In striking contrast to almost all the bouncing reported so far that the drop undergoes spreading and retraction in contact with the underlying solid before leaving the surface, drop impinging on our surface generates a pancake bouncing, namely the drop taking off close to its maximum lateral extension in a pancake shape without retracting, thereby resulting in significantly shortened liquid-solid contact time. The main goals of this project are to implement an integrated analytical, modeling and experimental approach to elucidate the fundamental mechanism responsible for the unique pancake bouncing and to harness the benefits of the short contact time for anti-icing application. In this project, we will perform theoretical analysis of the impact dynamics from both timescale and energy viewpoints and identify key structural features, drop size and hydrodynamics for the emergence of peculiar pancake bouncing. Moreover, we propose to develop multi-layered surface with graded spacing to achieve enhanced pancake bouncing. Finally, we will investigate the feasibility of harnessing pancake bouncing to suppress supercooled drop freezing at low temperatures.Our preliminary works on the development of superhydrophobic surfaces for multifunctional applications (Advanced Functional Materials, 2011; Physical Review Letters, 2012; Soft Matter, 2012; Scientific Reports, 2013; Small, 2014) lay important foundation for the implementation of the project with a proposed budget of 1320,000 HKD (~168,000 USD). If successful, the prospect of achieving novel pancake bouncing featuring efficient drop shedding by engineering superhydrophobic surfaces with special textures will not only advance our understanding of wetting phenomena, but also open up a new avenue for a broad range of industrial applications including anti-icing, dropwise condensation and self-cleaning.Preventing the formation/accumulation of ice on solid surfaces as well as promoting its easy detachment without energy input is of importance for a wide range of applications including in transportation, energy system, telecommunications and aerospace. The state of the art active ice mitigation approaches require substantial energy input and pose detrimental environmental impacts. Alternatively, passive approaches leveraging the surface wettability for anti-icing offer tremendous promises. Particularly, inspirations from natural nonwetting structures such as lotus leaves have accelerated the development of various superhydrophobic surfaces that enable fast detachment of drops before they are frozen.Recently, we discovered a very exciting and counterintuitive drop impact regime on a novel superhydrophobic surface with special textures. In striking contrast to almost all the bouncing reported so far that the drop undergoes spreading and retraction in contact with the underlying solid before leaving the surface, drop impinging on our surface generates a pancake bouncing, namely the drop taking off close to its maximum lateral extension in a pancake shape without retracting, thereby resulting in significantly shortened liquid-solid contact time. The main goals of this project are to implement an integrated analytical, modeling and experimental approach to elucidate the fundamental mechanism responsible for the unique pancake bouncing and to harness the benefits of the short contact time for anti-icing application. In this project, we will perform theoretical analysis of the impact dynamics from both timescale and energy viewpoints and identify key structural features, drop size and hydrodynamics for the emergence of peculiar pancake bouncing. Moreover, we propose to develop multi-layered surface with graded spacing to achieve enhanced pancake bouncing. Finally, we will investigate the feasibility of harnessing pancake bouncing to suppress supercooled drop freezing at low temperatures.Our preliminary works on the development of superhydrophobic surfaces for multifunctional applications (Advanced Functional Materials, 2011; Physical Review Letters, 2012; Soft Matter, 2012; Scientific Reports, 2013; Small, 2014) lay important foundation for the implementation of the project with a proposed budget of 1320,000 HKD (~168,000 USD). If successful, the prospect of achieving novel pancake bouncing featuring efficient drop shedding by engineering superhydrophobic surfaces with special textures will not only advance our understanding of wetting phenomena, but also open up a new avenue for a broad range of industrial applications including anti-icing, dropwise condensation and self-cleaning.