8 research outputs found
Moving charged particles in lattice Boltzmann-based electrokinetics
The motion of ionic solutes and charged particles under the influence of an
electric field and the ensuing hydrodynamic flow of the underlying solvent is
ubiquitous in aqueous colloidal suspensions. The physics of such systems is
described by a coupled set of differential equations, along with boundary
conditions, collectively referred to as the electrokinetic equations. Capuani
et al. [J. Chem. Phys. 121, 973 (2004)] introduced a lattice-based method for
solving this system of equations, which builds upon the lattice Boltzmann
algorithm for the simulation of hydrodynamic flow and exploits computational
locality. However, thus far, a description of how to incorporate moving
boundary conditions into the Capuani scheme has been lacking. Moving boundary
conditions are needed to simulate multiple arbitrarily-moving colloids. In this
paper, we detail how to introduce such a particle coupling scheme, based on an
analogue to the moving boundary method for the pure LB solver. The key
ingredients in our method are mass and charge conservation for the solute
species and a partial-volume smoothing of the solute fluxes to minimize
discretization artifacts. We demonstrate our algorithm's effectiveness by
simulating the electrophoresis of charged spheres in an external field; for a
single sphere we compare to the equivalent electro-osmotic (co-moving) problem.
Our method's efficiency and ease of implementation should prove beneficial to
future simulations of the dynamics in a wide range of complex nanoscopic and
colloidal systems that was previously inaccessible to lattice-based continuum
algorithms
Selective trapping of DNA using glass microcapillaries
We show experimentally that a cheap glass microcapillary can accumulate
{\lambda}-phage DNA at its tip and deliver the DNA into the capillary using a
combination of electro-osmotic flow, pressure-driven flow, and electrophoresis.
We develop an efficient simulation model for this phenomenon based on the
electrokinetic equations and the finite-element method. Using our model, we
explore the large parameter space of the trapping mechanism by varying the salt
concentration, the capillary surface charge, the applied voltage, the pressure
difference, and the mobility of the analyte molecules. Our simulation results
show that this system can be tuned to capture a wide range of analyte
molecules, such as DNA or proteins, based on their electrophoretic mobility.
Our method for separation and pre-concentration of analytes has implications
for the development of low-cost lab-on-a-chip devices.Comment: 9 pages, 4 figure
Reducing spurious flow in simulations of electrokinetic phenomena
Electrokinetic transport phenomena can strongly influence the behaviour of
macromolecules and colloidal particles in solution, with applications in, e.g.,
DNA translocation through nanopores, electro-osmotic flow in nanocapillaries,
and electrophoresis of charged macromolecules. Numerical simulations are an
important tool to investigate these electrokinetic phenomena, but are often
plagued by spurious fluxes and spurious flows that can easily exceed physical
fluxes and flows. Here, we present a method that reduces one of these spurious
currents, spurious flow, by several orders of magnitude. We demonstrate the
effectiveness and generality of our method for both electrokinetic
lattice-Boltzmann and finite-element-method based algorithms by simulating a
charged sphere in an electrolyte solution, and flow through a nanopore. We also
show that previous attempts to suppress these spurious currents introduce other
sources of error.Comment: 13 pages, 7 figure