This lecture will explore one of the most elementary yet subtle transport phenomena : osmosis. The phenomenon of osmosis is usually associated with the notion of osmotic pressure, as described by van 't Hoff. First, we'll look at the molecular nature of osmosis, particularly from a mechanical point of view.
This will be illustrated using the example of the kidney, which acts as an osmotic exchanger. We will discuss its impressive performance in terms of separation and energy cost.
We will then explore various osmotic processes beyond van 't Hoff : first diffusio-osmosis, which is an epi-osmotic process that takes place at the interfaces ; then osmotic diodes ; and finally an osmotic resonance phenomenon, when interactions within the nanopore are excited under external forcing.
By way of illustration, we will discuss recent experiments showing how these osmotic processes can be used to artificially design molecular motors mimicking the proton turbine.
