A microfluidic device for array patterning by perpendicular electrokinetic focusing

Abstract

This paper describes a microfluidic chip in which two perpendicular laminar-flow streams can be operated to sequentially address the surface of a flowchamber with semi-parallel sample streams. The sample streams can be controlled in position and width by the method of electrokinetic focusing. For this purpose, each of the two streams is sandwiched by two parallel sheath flow streams containing just a buffer solution. The streams are being electroosmotically pumped, allowing a simple chip design and a setup with no moving parts. Positioning of the streams was adjusted in real-time by controlling the applied voltages according to an analytical model. The perpendicular focusing gives rise to overlapping regions, which, by combinatorial (bio) chemistry, might be used for fabrication of spot arrays of immobilized proteins and other biomolecules. Since the patterning procedure is done in a closed, liquid filled flow-structure, array spots will never be exposed to air and are prevented from drying. With this device configuration, it was possible to visualize an array of 49 spots on a surface area of 1 mm 2 . This article describes the principle, fabrication, experimental results, analytical modeling and numerical simulations of the microfluidic chip.

Dielectrophoretic focusing of particles in a microchannel constriction using DC‐biased AC flectric fields

“…In this operation, dispersed particles are focused to a tight stream enabling subsequent detection and sorting [4][5][6]. Microfluidic particle focusing has been realized primarily by using hydrodynamic [7][8][9][10] or electrokinetic [11][12][13][14][15] sheath flow(s) to pinch the suspending medium and thus focus particles. Other than this flowassisted method, a variety of sheathless focusing approaches have also been demonstrated.…”

Modeling of cell sorting and rare cell capture with microfabricated biodevices

“…Electrokinetic focusing is one of the alternatives to hydrodynamic focusing, in which instead of pressure, electroosmotic flow (EOF) [37] is used for fluidic pumping. Beyond the typical plug shape of EOF, one of the most important advantages of electroosmotic focusing techniques is the lack of moving parts in the chip layout, reducing the risk of damage, while also decreasing cost.…”

“…Beyond the typical plug shape of EOF, one of the most important advantages of electroosmotic focusing techniques is the lack of moving parts in the chip layout, reducing the risk of damage, while also decreasing cost. Kohlheyer et al [37], Lin et al [38], and Li et al [39] Q6 used CFD simulations to analyze the distribution of the electric field inside a microfluidic chip. A recent publication [40] is especially interesting from the viewpoint of modeling and simulation of this phenomena.…”

Microflow cytometer incorporating sequential micro-weir structure for three-dimensional focusing

“…2-D focusing techniques are generally sufficient for continuous-flow particle sorters, even though the adhesion of some particles to the upper and lower channel walls may sometimes be a problem (Fu et al 2003;Kohlheyer et al 2008;Hairer and Vellekoop 2009). However, to optimize the sorting and counting performance of a microflow cytomer, the particles should be separated not only in the horizontal plane, but also in the vertical plane Lee et al 2009;Kim and Yoo 2009;Oakey et al 2010).…”