|Phone:||+49 711 685-63594|
|Fax:||+49 711 685-63658|
|Email:||ohickey _at_ icp.uni-stuttgart.de|
Institute for Computational Physics
I am interested in the simulation of electrokinetic phenomena, namely electrophoresis and electroosmotic flow, involving polymers. Particularly I am interested in simulating systems which have yet to be explored using molecular dynamics and the sometimes surprising results of the interplay between electrostatic and hydrodynamic interactions.
Implicit Electrohydrodynamics Using Lattice-Boltzmann and ESPResSo
During my time in Stuttgart in 2009 I developed an implicit scheme for simulating the electrohydrodynamics of polyelectrolytes which was later published in 2010. I have made a number of videos (with much help from Georg Rempfer) which illustrate some of the intricacies of electrokinetics.
Polymers subject to a constant force are said to be sedimenting. The polymers move through the fluid and drag the surrounding fluid along with it. Larger polymers move faster as the force (which is proportional to the length of the polymers) grows faster than the average size of the polymers. This can be clearly seen in the video below.
Comparing Electrophoresis to Sedimentation
If we compare the movement of polymers subject to an electric field (electrophoresis) with polymers subject to a constant force (sedimentation) there are distinct differences. Notably unlike in electrophoresis the sedimenting polymer perturbs the surrounding fluid and essentially drags the fluid within it at roughly the same velocity. This is caused by the drag force of the fluid on the polymer which also in turn deforms the polymer. Since the electrophoresing polymer does not produce drag with the surrounding fluid it does not deform as it moves through the fluid. The difference can be seen in the video below where the upper polymer undergoes electrophoresis while the lower one is sedimenting.
Free Solution Electrophoresis of Polyelectrolytes
This video shows the electrophoresis of charged polymers in free solution (bulk fluid without obstacles or a sieving matrix). The video illustrates two surprising points, namely polymers of different length all move with the same speed and the motion of the polymers do not perturb the surrounding fluid.
Hickey O.A., Modulating Electro-osmotic Flow with Polymer Coatings, Ph.D. thesis, University of Ottawa 2012 
Shendruk T.N., Hickey O.A., Slater G.W., Harden J.L.. Electrophoresis: When hydrodynamics matter, 2012 17 (2), Current Opinion in Colloid and Interface Science 
Hickey O.A., Holm C., Harden J.L. and Slater G.W., Influence of Charged Polymer Coatings on Electro-Osmotic Flow: Molecular Dynamics Simulations, 2011 44 (23), Macromolecules, pp 9455–9463 
Hickey O.A., Harden J.L., Holm C. and Slater G.W., Implicit method for simulating electrohydrodynamics of polyelectrolytes, 2010 105 (14), 148301, Physical Review Letters 
Slater G.W., Holm C., Chubynsky M.V., de Haan H.W., Dube A., Grass K., Hickey O.A., Kingsburry C., Sean D., Shendruk T.N. and Zhan L., Modeling the separation of macromolecules: a review of current computer simulation methods, 2009, Electrophoresis 20 (5), pp.792-818 
Hickey O.A., Harden J.L. and Slater G.W., Molecular Dynamics Simulations of Optimal Dynamic Uncharged Polymer Coatings for Quenching Electro-osmotic Flow, 2009, Physical Review Letters 102 (10), 108304 
Hickey O.A. and Slater G.W., The diffusion coefficient of a polymer in an array of obstacles is a non-monotonic function of the degree of disorder in the medium, 2007, Physics Letters, Section A: General, Atomic and Solid State Physics 364 (6), pp. 448-452 
Hickey O.A., Mercier, J-F, Gauthier, M.G., Tessier, F., Bekhechi S. and Slater G.W., Effective molecular diffusion coefficient in a two-phase gel medium, 2006, Journal of Chemical Physics 124 (20), 204903