My research interests span from the statics of wetting interfacial phenomena to the dynamics of liquid films and droplets wetting and dewetting during phase-change during both evaporation and condensation influencing heat transfer on a wide range of wettability and structured surfaces and at multiple-scales. Advanced surfaces with embedded and controlled functionalities as well as bioinspired functional surfaces and their intimate interactions with liquid droplets undergoing phase-change for the better understanding of micro- and nano-scale phase-change heat transfer encompass my ultimate goals.

Fundamental Physics of Fluid Wetting and Evaporation Phase Change

Interactions between liquids and solid surfaces are ubiquitous in nature and are relevant to many everyday life, industrial, biological, medical and pharmaceutical applications. Wettability, micro- and nano-structures, chemical heterogeneities, temperature and pressure play an important role on the intimate interactions between solid surfaces and liquids of importance to self-cleaning, anti-fogging, anti-icing or other applications. Some collaboration institutions include: Kyushu University (Japan), University of Bordeaux (France), Indian Institute of Technology Madras (India).

Figure from Fukatani et al., PRE 2016 - Raw Infrared thermography data data at an ambient temperature of 40 degrees Celsius and different relative humidity (a) RH = 35% and (b) RH = 90% at t = 10 s, 20 s, 30 s, 40 s, and 100 s.

Fundamental Physics of Fluid Wetting, Condensation Phase Change and Vapour Absorption

Micro- and nano-structured surfaces play a paramount role on the dynamics of triple-phase contact line during wetting and condensation phase-change. More specifically, wetting, nucleation, droplet growth, coalescence and shedding during evaporation/condensation are paramount for the design of more efficient heat transfer processes and energy systems. Both fundamental and applied efforts are being put here. Collaborations with renowned universities such as: University of Illinois at Urbana-Champaign (USA), Shanghai Jiao Tong University (China), Waterloo Institute for Nanotehcnology University of Waterloo (Canada), Stevens Institute of Technology (USA) are taking place in this topic.

(left) Figure from Orejon et al. Int. J. Heat Mass Transf. 2017 - Simultaneous Dropwise/Filmwise Condensation on hydrophilic structured pillared surfaces function of the pillar geometry parameters along with theoretical heat transfer.

(right) Figure from Wang et al. Phys. Chem. Chem. Phys. 2019 - Water vapor uptake into hygroscopic lithium bromide desiccant droplets: mechanisms of droplet growth and spreading Back Cover.

Effect of Surrounding Environment on Wetting and Phase-Change

A new avenue for the manufacturing of micro-/nano-structured metallic superhydrophobic surfaces via ambient exposure has been demonstrated as a consequence of the adsorption of Volatile Organic Compounds (VOCs) ever present in the environment, which have led to high impact factor publications, invited presentations and a Fellowship application. The effect of surrounding environment has been overlooked in the past decades. We demonstrate the strong interplay between ambient composition on droplet-surface interactions and on the dynamics of evaporation and condensation. Collaborations in this are involve: University Illinois Urbana-Champaign (USA), Maryland University (USA), Tsinghua University (China), Iowa State University (USA), Kyushu University (Japan).

Figure from Xiao et al. ACS Nano 2019 - Wetting to non-wetting transition on hierarchical copper oxide (CuO): θ_a (deg), vs. VOCs exposure time, t (days), enabling coalescence-induced droplet jumping.

Functional Surfaces for Droplet Manipulation and Control via Wettability Patterning or Surface Structure 

The fine control and tune of wettability and surface structure patterns inducing wettability gradients can be further exploited for the accurate manipulation and migration of liquid droplets and films on solid surfaces of imoprtance to microfluidic applications amongst others. Collaborations in this area include: University of Bordeaux (France) and Waterloo Institute for Nanotehcnology University of Waterloo (Canada), amongst others.

(left) Figure from Orejon et al. RSC Advances 2016 - Environmental Scanning Electron Microscopy ESEM image and schematics of droplet held on the edge of the micropillar migrating to the hydrophobic side-wall to the hydrophilic top surface. Scale bar is 50 μm.

(right) Figure from Zhao et al. APL 2020 - Snapshots of a droplet moving across the boundary. Blue dots represents the droplet center of mass and dashed lines the position of the boundary.