Particle-laden interfaces (PLIs) are ubiquitous in nature and industry, being used in applications such as pickering emulsions and mineral separations. Particle-coated droplets, a.k.a. “liquid marbles”, are a specific class of PLIs which allow encapsulation and movement of small discrete volumes. Understanding the interplay between the particle shell meso-structure and fluid and external forces is crucial to maintaining integrity. We use high-speed video imaging and simple analytical arguments to understand the dynamics of liquid marbles. This fundamental work is important for the current wide range of novel applications of liquid marbles. Specific research projects in this rich area are:
Impact/arrested shape formation
When liquids marbles crash on a solid substrate, do they remain intact or shatter? What determines the outcome? We are interested in understanding the roles of inertia, particle shell characteristics (thickness, particle size, density etc.) and fluid properties. An interesting observation is the formation of arrested shapes (see the GIFs below and our recently accepted paper in Phys. Rev. E).
Crushing and necking
To complement our impact studies and provide a more comprehensive understanding of marble resilience, we are conducting a systematic study of controlled compression, where a marble is gently squeezed. If compressed beyond approximately 50%, the shell will rupture. However, if the marbles are compressed and released, they do not always return to their original shape. We are currently discovering the key mechanisms at play and the limits of this phenomenon (see GIF below).
Non-coalescence
Two particle-laden interfaces brought together do not coalesce easily, like pure liquid drops. In fact, they can withstand a considerable normal compression as shown in the video below. Our goal here is to quantify this resilience and understand the role of the particle shell structure.
Snap-in Dynamics
In previous works, we studied the formation of liquid marbles during drop impact onto powder surfaces. Now, we are trying to understand liquid marble formation in more detail – such as the initial attachment of particles to a liquid interface – the so-called snap-in effect.
