Theory of electrohydrodynamic effects in microfluidics; desalination

Contacts:

Henrik Bruus, DTU Nanotech, 4525-6399 (bruus@nanotech.dtu.dk)

Mathias Bækbo Andersen, DTU Nanotech, 4525-5742 (mbaan@nanotech.dtu.dk)

Web: http://www.nanotech.dtu.dk/microfluidics

Sketch of a model desalination system with the potential on the porous electrode. (b) At sufficiently high voltages a desalinated (salt-free) layer develops in front of the electrode. Adapted from Biesheuvel and Bazant, Phys Rev E 81, 031502 (2010).

Microfluidics deals with the flow of li­quids in systems of length scales typi­cal­ly in the range from 100 nm to 1 mm. As experimental tools have been refined the previous decade, a range of new phe­no­me­na has been discovered, which are not yet fully understood from a theoretical point of view.

An important class of problems rela­tes to the behavior of electrolytes (salt water) in­flu­enced by external electric fields. We will in particular focus on desalination, a process which already today is important to ensure clean water in dry parts of the world.

In this theoretical and numerical project you will be part of our theoretical research group, which, in a new collaboration with our experimental partners at MIT, is investigating new ways of obtaining desalination using microporous systems, see Figure.

After an introduction to the necessary hydrodynamics, electrodynamics, and thermodynamics, you will study simplified analytical models of the system and later do full numerical simulations. You will learn to use the general soft­ware COMSOL for solving coupled, non-linear, partial differential equations. The goal of the project is to provide a basic theoretical physics analysis of the system and to help us find designs for optimal desalination.