Research

A brief overview of my ongoing research projects.



Active contraction in biological fiber networks

The forces that living organisms exert to move and change shape originate at the nanometer scale, from the power strokes exerted by motor proteins. These forces are transmitted to larger scales by networks of stiff, fibrous polymers, both at the intra- and extra-cellular level. What are the physical laws that govern such force transmission?


With Martin Lenz (Orsay) and Chase Broedersz (Munich).



Force transmission in collagen  

Collagen is the most abundant protein in our body. It forms extracellular fiber networks which are, for instance, responsible for most of the elastic properties of the skin. In this project, we design new techniques to measure stress in such networks, and apply them to investigate how the forces exerted by strongly contractile cancer cells propagate and stiffen the network.


With Ming Guo (MIT, experiments), Martin Lenz (Orsay) and Chase Broedersz (Munich). Image courtesy of Ming Guo.




Intracellular phase transitions

 The recent discovery of membrane-less organelles inside eukariotic cells, such as the pyrenoid that concentrates carbon in unicellular algae, sparks a number of deep physical questions: What mechanism is responsible for such liquid-liquid phase separation? How do cells control it?  
With Martin Jonikas (experiments), Bin Xu and Ned Wingreen (Princeton University).







Local structure in supercooled liquids and glasses

In a molecular liquid, some local arrangements of molecules are more stable than others, and will tend to be found more and more as the liquid is slowly cooled down. What role do these favoured local structures play in the stability of a supercooled liquid against crystallization? 

With Peter Harrowell (Sydney).






Self-assembly of proteins and colloids

When a dilute solution of many identical particles with attractive interactions is slowly cooled down, these particles will aggregate. The shape of such aggregates, and in particular its dimensionality, depends strongly on the shape of these particles. What connects the geometry of a particle to the morphology of its self-assembled aggregates?

With Martin Lenz (Orsay).



Geometrical frustration in dense and dilute systems

Frustration, in an optimization problem, refers to the impossibility to simultaneously satisfy all constraints of a system. When considering the spatial arrangement of particles in a condensed matter problem, some locally optimal configurations may not be extended to cover the whole available space: for instance, tiling the plane with pentagons without leaving gaps is impossible. Can we construct a mathematical framework to quantify geometric frustration?