To achieve motion beyond diffusion, numerous soft particles (cells, viruses, DNA-coated colloids) rely on random attachement and detachment of sticky ligands on an opposing surface. Understanding the overall motion of these particles is critical to probe the biological and physical processes at stake (assembly, targeted arrest). However, attachment dynamics often occur on much shorter time scales and length scales then the overall motion, making suh predictions challenging.

In Nature, transport of specific compounds is often mediated between small compartments via tiny channels or holes. Because these transport processes concern only a few number of particles, they are inherently subjected to fluctuations (of the number of particles). How large are these fluctuations ? How do biological systems resist or harness these fluctuations ?

(Image credits: Jalene Lu) Osmosis is a universal phenomenon occurring in a broad variety of processes. It is both trivial in its fundamental expression, yet highly subtle in its physical roots. Pushing the fundqmentql understqnding of osmosis, it is possible to explore new perspectives in a variety of fields, and find applications where advanced osmotic processes show great promises.

In Nature, exceptional permeability and selectivity properties are reached in ion channels. The paradigm change as compared to nanoscale technology is that these biological filters are out-of-equilibrium, submitted to either thermal or active fluctuations – for example of the pore constriction. We investigated how out-of-equilibrium fluctuations of a pore affects translocation dynamics, and found regimes of enhanced selectivity and transport. These results open up the possibility that transport across membranes can be actively tuned by external stimuli, with potential applications to nanoscale pumping, osmosis and dynamical ultrafiltration.

Measurements and simulations have found exceptional transport properties for water and ions through narrow pores such as carbon nanotubes. The exact mechanism of transport inside nanotubes continues to be debated because of the limited number of experimental results, and the fact that continuum theories may not be used at these scales. We have made significant effort in designing very accute experiments in single nanoscale pores and investigating how discrete effects come into play in these systems. Nanofluidics is truely the frontier at which the continuum picture of fluid mechanics meets the atomic nature of matter.

(photo credit: Natalie Andrew) Physarum Polycephalum is a slime mold growing as a mostly planar network of veins encapsulating periodically pumped fluid flow with nutrients and genetic material. Together with the Biological Physics and Morphogenesis (BPM) group, we are interested in understanding the growth and pruning dynamics of this individual. Learning from this individual may help to identify patterns that may allow to build hypothesis for blood vasculature morphogenesis.