(From left) Dr Xin Tang, Professor Liqiu Wang and Dr Xing Han
Professor L.Q. Wang, Chair Professor of Thermal-Fluid Sciences and Engineering of the Department of Mechanical Engineering and his teams had worked on two research topics “Slippery damper of an overlay for arresting and manipulating droplets on nonwetting surfaces” and “Furcated droplet motility on crystalline surfaces”. Both papers have been published by Nature Communications and Nature Nanotechnology on May 26, 2021 and July 19, 2021 respectively.
Details of the papers:
Slippery damper of an overlay for arresting and manipulating droplets on nonwetting surfaces
Xing Han, Wei Li, Haibo Zhao, Jiaqian Li, Xin Tang & Liqiu Wang
Article in Nature Communications 12, Article number: 3154 (2021)
Abstract:
In diverse processes, such as fertilization, insecticides, and cooling, liquid delivery is compromised by the super-repellency of receiving surfaces, including super-hydro-/omni-phobic and superheated types, a consequence of intercalated air pockets or vapor cushions that promote droplet rebounds as floating mass-spring systems. By simply overlaying impacting droplets with a tiny amount of lubricant (less than 0.1 vol% of the droplet), their interfacial properties are modified in such a way that damper-roller support is attached to the mass-spring system. The overlayers suppress the out-of-plane rebounds by slowing the departing droplets through viscous dissipation and sustain the droplets’ in-plane mobility through self-lubrication, a preferential state for scenarios such as shedding of liquid in spray cooling and repositioning of droplets in printing. The footprint of our method can be made to be minimal, circumventing surface contamination and toxification. Our method enables multifunctional and dynamic control of droplets that impact different types of nonwetting surfaces.
Link: https://www.nature.com/articles/s41467-021-23511-3
Furcated droplet motility on crystalline surfaces
Xin Tang, Wei Li & Liqiu Wang
Article in Nature Nanotechnology (2021): https://doi.org/10.1038/s41565-021-00945-w
Abstract:
Directed liquid motion has been conventionally mediated by functionalizing chemical inhomogeneity or texturing topological anisotropy on target surfaces. Here we show the self-propulsion of droplets that furcated in well-defined directions on piezoelectric single crystals in the absence of any apparent asymmetry or external force. By selecting the crystal plane to interface with the droplets, the thermoelastic–piezoelectric interplay yields intricate electric potential profiles, enabling various forms of self-propulsion including unidirectional, bifurcated and trifurcated. This effect originates from an anisotropic crystalline structure that generates contrasting macroscopic liquid behaviours and is observed with cold/hot and volatile droplets. Intrinsically oriented liquid motions have broad applicability in processes ranging from soft matter engineering, autonomous material delivery and thermal management to biochemical analysis.
Link: https://www.nature.com/articles/s41565-021-00945-w