Croucher Scholar reimagines the water droplet

11 May 2022

Croucher scholar Professor Anderson Shum is harnessing the physical properties of water droplets to reimagine its uses.

Water drops are collections of liquid water bounded by free surfaces that are dependent on their surface tension, or “skin”, to hold their shape.

In their basic form, water drops are spherical, but forces such as air flow and gravity can transform the droplet’s shape.

Professor Anderson Shum (Croucher Senior Research Fellow 2020) of the Department of Mechanical Engineering at Hong Kong University is working in a field of physics which aims to repurpose the droplet.

“The initial fascination for me came from observing water droplets everywhere. Now we have techniques that allow you to directly control their formation and manipulate them,” Shum said.

“The possible applications are manifold. By controlling the interface between droplets, you can control the release of active ingredients — so this can be applied to drugs, it can be applied to flavours, it can be applied to fragrances, it can be applied to a lot of different things.”

Pioneering Work

Shum and his team have also used droplet manipulation techniques in their study of liquid immiscibility – when two liquids are incapable of mixing or attaining homogeneity.

“We add additives to the water at high enough concentrations which triggers a phase separation,” he said, referring to a process that creates two distinct phases from a single homogeneous mixture.

Once these liquids become immiscible, the team studies the dynamics of their unique interfaces.

“When the liquids meet at the interface, the reactions can lead to the assembly of new bio- and cyto-compatible materials,” Shum said. These designer biomaterials can be assembled for precision delivery of tunable quantities of active ingredients.

Driven by Curiosity

It is clear that one of the driving forces behind Shum’s research is a fascination and a curiosity for water droplets, which Shum has managed to transmit to his research students.

“I was interested in this field because of the possibilities that come through playing with liquid droplets in a visual and understandable way. They are just so fascinating to observe and to be able to shape and understand them is something that gives me a lot of joy,” Shum stated.

“Many of my research students are now coming up with ideas I could not have come up with when I was a student. That is the really fun part for me.”