Bubbles and Droplets for Clean Water and Energy Technologies

Distinguished Series Academic Track

with Xuehua Zhang,
University of Alberta

January 30, 2026
12:30 PM – Goodwin 190

This seminar examines how microdroplets and microbubbles can be engineered to intensify interfacial reactivity in two chemically distinct, yet mechanistically aligned, systems. I will highlight bubble and droplet dynamics for accelerating interfacial reactions, providing scalable pathways toward efficient hydrogen generation and plasma-enabled water-treatment technologies.

In the first system, hydrogen bubbles arise from a droplet-mediated interfacial reaction. Liquid organic hydrogen carriers (LOHCs) offer a compelling route for hydrogen storage, transport, and on-demand release, but their use in aqueous environments is often limited by phase immiscibility and slow interfacial kinetics. I will present a strategy that overcomes these barriers using binary LOHC–alcohol microdroplets as microscopic reactive entities. Upon contact with NaOH solution, the droplet reaction generates an increase in hydrogen production rate compared with the immiscible baseline. The enhancement is strongest for polymeric LOHC/long-chain alcohol mixtures and is further amplified in the presence of cationic surfactants. Using single-droplet imaging, we identify a sharp transition in bubble-formation pathways, from in-droplet nucleation at low mixing ratios to clustered/on-droplet growth at higher ratios, revealing a direct link between bubble dynamics, interfacial renewal, and hydrogen-generation efficiency.

In the second system, microbubbles are used to intensify plasma–liquid mass transfer in cold plasma activation of water within a recirculating (closed-loop) contactor. Air plasma generates reactive oxygen and nitrogen species (RONS) and other reactive intermediates, which are then delivered into water through microbubble injection to enhance solvation, dissolution, and aqueous conversion. I will show how interfacial transport and bubble-mediated residence time govern reactive-species uptake and downstream chemistry, establishing practical operating levers for plasma-assisted nitrogen fixation into aqueous species relevant to decentralized water treatment.

Xuehua Zhang is a Professor at the University of Alberta, a Fellow of the Canadian Academy of Engineering, and the Tier 1 Canada Research Chair in Soft Matter and Interfaces. She earned her PhD in Biomedical Engineering from Shanghai Jiao Tong University, China. Her international career began with an Endeavour Postdoctoral Fellowship at the Australian National University. She was subsequently awarded a highly competitive Australian Postdoctoral Fellowship at the University of Melbourne under the supervision of Professor William Ducker, followed by a prestigious Future Fellowship. In 2014, Professor Zhang was appointed Associate Professor at RMIT University, while concurrently holding a part-time professorship at the University of Twente in the Netherlands. She joined the University of Alberta in 2017. Her research group employs a multidisciplinary approach combining experimental, theoretical, and numerical methods to advance the understanding in microscopic bubbles and drops in multicomponent systems, the evaporation dynamics of multicomponent droplets, and clean energy solutions and cold plasma technology for advanced water treatment.