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A periodic array of nano‐scale parallel slats for high‐efficiency electroosmotic pumping
Author(s) -
Kung ChunFei,
Wang ChangYi,
Chang ChienCheng
Publication year - 2013
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.201300135
Subject(s) - dimensionless quantity , perforation , transverse plane , electrokinetic phenomena , mechanics , volumetric flow rate , materials science , flow (mathematics) , analytical chemistry (journal) , chemistry , physics , composite material , nanotechnology , structural engineering , chromatography , engineering , punching
It is known that the eletroosmotic ( EO ) flow rate through a nano‐scale channel is extremely small. A channel made of a periodic array of slats is proposed to effectively promote the EO pumping, and thus greatly improve the EO flow rate. The geometrically simple array is complicated enough that four length scales are involved: the vertical period 2 L , lateral period 2 a L , width of the slat 2 c L as well as the D ebye length λ D . The EO pumping rate is determined by the normalized lengths: a , c , or the perforation fraction of slats η = 1 − ( c / a ) and the dimensionless electrokinetic width K = L / λ D . In a nano‐scale channel, K is of order unity or less. EO pumping in both longitudinal and transverse directions (denoted as longitudinal EO pumping (LEOP) and transverse EO pumping (TEOP), respectively) is investigated by solving the D ebye– H ückel approximation and viscous electro‐kinetic equation. The main findings include that (i) the EO pumping rates of LEOP for small K are remarkably improved (by one order of magnitude) when we have longer slats ( a ≫ 1 ) and a large perforation fraction of slats ( η > 0.7); (ii) the EO pumping rates of TEOP for small K can also be much improved but less significantly with longer slats and a large perforation fraction of slats. Nevertheless, it must be noted that in practice K cannot be made arbitrarily small as the criterion ofφ c ≈ 0 for the reference potential at the channel center put lower bounds on K ; in other words, there are geometrical limits for the use of the P oisson– B oltzmann equation.