International Institute for Carbon‐Neutral Energy Research (WPI‐I2CNER)
Kyushu UniversityTitle

Droplets on Micro‐decorated Surfaces:
Wetting and Phase‐Change
Speaker Prof. Daniel Orejon

I²CNER Webinar

Time&Date

Institute for Multiscale Thermofluids, School of Engineering,
University of Edinburgh, UK

16:00 PM(JST), Wednesday, October 12th, 2022

Abstract
The close interactions between liquids droplets and films, and solid surfaces are ubiquitous and play a paramount role inmany everyday domestic and industrial applications closely related to thermal management, water treatment and harvesting,energy generation, etc.
In this talk I introduce efforts focusing on the systematic fundamental understanding of solid surface intrinsic wettability andmicro‐features, fluid surface tension, as well as the surrounding ambient, on the wettability and phase‐change of small sized
droplets following different micro‐fabrication approaches. Deterministic deep reactive ion etching, stochastic wet etchingand soft lithography enabling the replication of either stochastic or deterministic features are presented. Droplets ondeterministic homogeneous structured surfaces adopt different wetting regimes and geometries, which can be tailored byvarying the surface tension of the fluid or the surface ambient exposure. The wetting regime and droplet geometry
eventually play a role on the evaporation mode and on the deposits.
The use of soft‐lithography for the replication of the deterministic structures of the Dalenii or dragon's head sword lily’s leaf
are also introduced and the performance of the replicated surfaces under condensation phase‐change and fog harvesting arecompared and discussed. Further, easy and scalable chemical etching enabling the growth of stochastic hierarchical features
is also studied. This process is able to create two different surfaces that resemble the lots leaf “super‐repellent” and the rose
petal “sticky” wetting behaviors. The wettability, wetting regime and condensation performance on these surfaces can also
be tailored depending on the exposure to the ambient conditions. Last, the synergistic cooperation of wettability gradientsurfaces and low adhesion lubricant infused surfaces and the use of lubricant infused phase‐change materials where thewettability, adhesion and heat transfer can be tailored via the phase of the infused material are also briefly reviewed.
Wetting and non‐wetting surfaces and mechanisms introduced here suggest promising capabilities for microfluidics, self‐cleaning, thermal management as well as condensation phase‐change applications.

About the Speaker
Daniel Orejon (Dani) holds a 5‐year bachelor’s degree in Environmental and Industrial Chemical Engineering from theUniversity of Seville (Spain). After graduating, Dani spent a year as Graduate Research Assistant at the Institute for Energy
Systems at the University of Edinburgh (UoE) and thereafter he completed his PhD on the fundamentals of evaporation
phase‐change at the droplet scale at the Institute for Materials and Processes at the UoE in 2013. Right after, Dani joined theInternational Institute for Carbon‐Neutral Energy Research (WPI‐I²CNER) at Kyushu University in Japan as a Post‐Doctoral
Research Associate where he shifted his research efforts towards condensation phase‐change as well. In 2016, he became
Assistant Professor at I²CNER Kyushu University (Japan) and 2 years later, he joined the Institute for Multiscale Thermofluids(IMT) at the UoE as a Lecturer in Chemical Engineering. Dani is currently a Senior Lecturer and serves as School Postgraduate
Progression Committee representative for the IMT and as Teaching Laboratory Manager for the Chemical Engineering
Discipline. In addition, Dani has been appointed as WPI‐I²CNER Visiting Associate Professor, Associate Editor for theInternational Journal of Heat and Mass Transfer, and Fellow of the Higher Education Academy.
Dani’s research interests embrace interfacial phenomena between liquid films/droplets and solid surfaces paying special
attention to the effect of surface wettability and structure, liquid nature and surrounding environment on the fundamentals
mechanisms of wetting and spreading encompassing evaporation and/or condensation phase‐change. He focuses on therelevant interactions at different length‐scales from the micro‐ to the nano‐scale as well as on the thermophyiscal propertiesof all three solid, liquid and gas phases present, for interfacial mass and thermal transport related applications. Dani received
the Young and Early‐Career Scientists Kakenhi award twice, has received a Royal Society Research Grant and is currently
participating in the SciSpacE Microgravity Application Promotion Programme from the European Space Agency (ESA).

Registration https://zoom.us/webinar/register/WN_LhA-GZV1S1aazaEas0mJfg
HostProf. Yasuyuki Takata
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