Electroosmosis and electrophoresis are considered to be the main phenomena for transport of aqueous liquids and particles in microfluidic devices because field-based techniques do not require any moving parts and can be incorporated more favorably into micro-analytical systems. In contrast to traditional applications involving relatively low fields and highly viscous media, the use of micron-sized channels enables one to employ strong fields (up to ~ kV/cm) and use low-viscous fluids since undesirable field effects are suppressed in such tiny channels. Under certain conditions, the interparticle electrical and hydrodynamic interactions drastically affect the suspension behavior in a microchannel due to its small dimensions. The use of these many-body effects would broaden substantially the range of applications of fields for the manipulation and control of particles and fluids in microdevices. Quantification of the motion of fluids and suspended particles in microchannels is critical for the design and optimization of electrokinetic microfluidic devices. We report (i) a method for measuring the fluid electroosmotic mobility of microchannel surfaces and the electrophoretic mobility of particles in strong DC and low-frequency AC fields and (ii) observations of the reversible aggregation of particles in a microchannel that can be tuned by varying the field strength and frequency.
Journal: TechConnect Briefs
Volume: 1, Technical Proceedings of the 2005 NSTI Nanotechnology Conference and Trade Show, Volume 1
Published: May 8, 2005
Pages: 191 - 193
Industry sectors: Advanced Materials & Manufacturing | Medical & Biotech