Electrophoretic Separation of Bioparticles through Entropic Barriers
Date Issued
2009
Date
2009
Author(s)
Cheng, Kuang-Ling
Abstract
Abstract The size separation of Brownian particles with the same -potential in an electrophoretic microchannel with alternating thick regions and narrow constrictions is studied theoretically. The electrophoretic mobility is field-dependent and generally increases with field strength. In weak fields, Brownian diffusion dominates and the migration is controlled by the entrance effect. Therefore, smaller particles migrate faster than larger ones. The separation resolution worsens as the field is increased. The results of simulation indicates that the greater field and smaller thick region depth raise separation speed while the smaller period length of the nanofilter enhances the separation resolution. In strong fields, however, the particle tends to follow electric field lines. Smaller particles are susceptible to Brownian motion and thus influenced by the nonuniform electric field in the well significantly. As a result, larger particles possess higher mobility. Brownian escape from a spherical cavity through small holes and force-driven transport through periodic spherical cavity have also been investigated by Brownian dynamic simulations and scaling analysis. The mean first passage time and force-driven mobility are obtained as a function of particle diameter , hole radius ， cavity radius , and external field strength. In the absence of external field, the escape rate is proportional to the exit effect. In weak fields, Brownian diffusion is still dominant and the migration is controlled by the exit effect. Therefore, smaller particles migrate faster than larger ones. In this limit the relation between Brownian escape and force-driven transport can be established by the generalized Einstein-Smoluchowski relation. As the field strength is strong enough, the mobility becomes field-dependent and grows with increasing field strength. As a result, the size selectivity diminishes.he separation of bead-spring polymers with different lengths but in an electrophoretic microchannel with alternating thick regions and narrow constrictions is studied by Brownian dynamics simulations. The result is similar to spherical particles. For Rouse polymers, Brownian diffusion is dominant and the migration is controlled by the exit effect under weak fields. As a result, shorter polymers migrate faster than longer ones. However, the situation is reversed under strong fields. The polymers are likely to follow electric field lines. Shorter polymers are influenced by Brownian motion. Therefore longer polymers migrate faster than shorter ones. We show that the coupling mechanism is Brownian diffusion and force-driven migration. For , polymers are entropically trapped in the thick regions and able to escape driven by an electric field. The trapping lifetime is length-dependent. In agreement with reported experimental results, longer DNA molecules have higher electrophoretic mobility. We show that the coupling mechanism between transverse diffusion and kinetic escape by deformation is responsible for this counterintuitive behavior. For each escape attempt, the probability for longer polymers to be successfully dragged through narrow constriction before the diffuse away form the entrance increases as chain length increases. Our simulation results agree with the experimental observations in periodically constricted microchannels. Our theoretical results provide useful guidance for design of a microchannel device based on periodic entropic barriers for efficiently separation a mixture of bioparticles based on size differences.
Subjects
electrophotetic
entropic barriers
Brownian dynamics simulation
bioparticles
Brownian motion
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-98-D90524004-1.pdf
Size
23.53 KB
Format
Adobe PDF
Checksum
(MD5):b2ccc2b4d77b4fff4d8ca64a5147250a