Van der Waals colloquium by prof. Eric Dufresne from ETH Zurich (Switzerland) on "Putting the Squeeze on Phase Separation". Eric's lab looks to living systems to inspire and inform experiments revealing the physics of soft materials, with a current emphasis on supramolecular organization, mechanics and interfaces.

Abstract: Living organisms produce optical and mechanical metamaterials.  These intricate nano- and micro-structures rival the best we can manufacture in a clean room, yet they are constructed from naturally abundant resources with sustainable low-energy processes.   Made from a wide variety of organic and inorganic components, these materials can be found across nature, from single-celled organisms to vertebrates.   In recent decades, basic research has revealed many of the structure-property relationships governing their function, and inspired a wealth of synthetic structures that mimic them.  However, an essential question remains:  how do living systems precisely control the structure of materials at the nano- and micro-scales?

In this talk, I’ll introduce some fascinating structures found in algae and birds.  Although the former are made of silica, and the latter of protein, both structures are thought to share a common physical origin: phase separation.  Phase separation is a generic process where a mixture is destabilized and its components spontaneously create multiple domains with different chemical compositions or physical structures.  While nano- and micro-architectures naturally emerge during any classical phase separation process, interfacial energy destabilizes them, driving coarsening as the system approaches thermodynamic equilibrium.  I will describe our recent experiments showing how elastic forces that emerge during phase separation can prevent coarsening and control the size, shape, and stability of micro- and nano-domains.

The Joan van der Waals colloquium is an ongoing bi-weekly lecture series, organized by LION. As all speakers are instructed to give an accessible lecture for everyone, these lectures aid in getting a broader view of physics. Each colloquium is preceded by an opening act: a PhD student or postdoc from LION and a different field than the invited speaker, to give a 10-min presentation. After the colloquium, there is a chance to meet your colleagues and participate in discussions at the borrel. More information can be found here.