Brisbane Transparent Lab: Optimising Flows in Nanochannels

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Interested in fluid dynamics at the nanoscale? You won’t want to miss this seminar by guest speaker, Dr Laurent Joly.

Dr Laurent Joly is a theoretician of soft condensed matter working at the University of Lyon 1, France. His activities concern the optimization of transport in micro and nanofluidic systems, where surface effects and molecular details play a crucial role. To tackle these questions, he combines analytical developments and numerical simulations at different scales. He has worked on liquids at complex interfaces and interfacial heat transfer at the nanoscale. He has now taken a particular interest in flows of nanoconfined liquids and their coupling to ionic transport. He investigates surface effects, with an expertise on liquid/solid friction and hydrodynamic slip, and the limits of continuum descriptions at the nanoscale.

Host: Professor Debra Bernhardt

Presenter: Laurent Joly, University of Lyon

Title: Optimising Flows in Nanochanels: Surface Friction and Entrance Effects

Date: Friday 31 January 2014

Time: 11:00am – 12:00pm

Venue:
AIBN Building (75)
Level 1 Seminar Room, Corner College and Cooper Road
University of Queensland, St Lucia

Abstract:

Liquids confined at nanometric scales behave in surprising ways, unexplained by macroscopic theories. A striking example can be found in nature with aquaporins: these biochannels selectively conduct water across cell membranes, with a permeability greater than the predictions of macroscopic hydrodynamics. This large permeability has also been observed in carbon nanotube membranes, with important applications in water desalination, ultrafiltration, energy harvesting, etc. These new behaviors arise from the increased role of surfaces and, when the confinement approaches the molecular size, from effects of the molecular detail. Both surface effects and molecular effects can be used to optimize the efficiency of nanofluidic systems, and to design new devices.

In the first part of this talk, I will show that the fast flow of liquids through CNT membranes can be attributed to their extremely small friction at the nanotube inner walls, and discuss the molecular origin of this ultra-low liquid/solid friction. I will then turn to another important mechanism limiting flows at the nanoscale: indeed, for nanochannels whose inner dissipation is extremely low, the overall permeability is also strongly limited by viscous dissipation at the entrances. I will discuss the significance of these entrance effects through two examples. Firstly, I will present molecular dynamics simulations of the capillary uptake of water by a carbon nanotube, and show that the filling dynamics is limited by entrance effects. I will then present recent work investigating aquaporins’ hourglass shape, and showing that the latter corresponds to an optimum for entrance viscous dissipation.