Particle separation is important in chemical and biomedical analysis. Among all particle separation approaches, microstructure filtration which based particles size difference has turned into one of the most commonly methods. By controlling the movement of particles, dielectrophoresis has also been widely adopted in particle separation. This work presents a microfluidic device which combines the advantages of microfilters and dielectrophoresis to separate micro-particles and cells. A three-dimensional (3D) model was developed to calculate the distributions of the electric field gradient at the two filter stages. Polystyrene particles with three different sizes were separated by micropillar array structure by applying a 35-Vpp AC voltage at 10 KHz. The blocked particles were pushed off the filters under the negative dielectrophoretic force and drag force. A mixture of Haematococcus pluvialis cells and Bracteacoccus engadinensis cells with different sizes were also successfully separated by this device, which proved that the device can separate both biological samples and polystyrene particles.
Ion
transport in nanofluidic devices and biological ion channels are highly
dependent on the local environmental conditions in the electrolyte
solution. Many life processes in living systems are in dynamic electrolyte
solutions, and many of them are self-oscillated. Tuning ion transport
through a nanofluidic diode by the self-oscillating chemical reactions
is demonstrated by modeling the electrokinetic ion transport process
with a validated continuum model, which includes the time-dependent
Poisson–Nernst–Planck equations for the ionic mass transport
of multiple ionic species with both volumetric and surface chemical
reactions, and Stokes equations for the flow field. A pH oscillator
caused by oscillating chemical reactions (i.e., bromate–sulfite–ferrocyanide
system) is added at the tip side of the nanopore to periodically change
its surface charge properties, consequently tuning the ion selectivity
and ion transport through the nanopore. Results show that both the
surface charge density of the nanopore and the electrokinetic ion
transport phenomena oscillate simultaneously with the pH oscillation
generated by the self-oscillating chemical reactions. The numerical
results obtained by our model qualitatively agree with the published
experimental observations.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.