Measurement and manipulation in microchannels using AC electric fields




Wood, Paul G.

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In this work, alternating current (AC) electric fields are used in combination with microfluidics to manipulate micro- and nano-sized particles and to probe the electrical characteristics of microchannels with potential application in portable diagnostics. This work was carried out as contribution to a collaborative research project involving researchers from chemistry, electrical engineering and mechanical engineering at the University of Victoria, in addition to researchers from the BC Cancer Deeley Research Centre. The manipulation of particles or cells within a microchannel flow is central to many microfluidic applications. In the context of diagnostics that utilize antibodies in serum, for example, the removal of cells from the sample is often required. Continuous removal of particles and cells is particularly critical in the case of flow-through nanohole array based sensing, as these serve as fine filters and thus are very susceptible to clogging. In this work, chevron shaped, interdigitated electrodes are used to produce dielectrophoretic forces in combination with hydrodynamic drag to displace particles from their corresponding streamlines to the center of a microchannel. Analytical and finite element modeling are used to provide insight into the focusing mechanism. Dielectrophoresis (DEP) also offers opportunities for particle manipulation in combination with porous media. In this preliminary work, the viability of dielectrophoresis tuned nano-particle transport in a nanohole array is investigated through analytical and numerical modeling. The effects of hydrodynamic drag and Brownian motion are considered in the context of applied voltage, flow rate and particle size. Preliminary flow-through tests are performed experimentally as proof of concept. The final contribution focuses primarily on external infrastructure that enables AC microfluidic diagnostics, with particular relevance to portable device applications and so-called point-of-care devices. Cell phones, and mp3 players are examples of consumer electronics that are easily operated and are ubiquitous in both developed and developing regions. Audio output (play) and input (record) signals are voltage-based and contain frequency and amplitude information. Audio signal based concentration, conductivity, flow rate, and particle detection measurements are demonstrated in a microfluidic platform.



microfluidics, nanofluidics, dielectrophoresis, impedance analysis, point-of-care diagnostics