We have developed a dielectrophoretic (DEP) gate for manipulating suspended particles in liquids using electric fields. Differences in polarizability between the particle and the fluid leads to body-forces on the particles that enable preconcentration, routing, and transport of particles in fluids. Lateral transport can also be accomplished by shifting electric-fields in an array of interdigitated microelectrodes.
We have developed a dielectrophoretic (DEP) gate for manipulating suspended particles in liquids using electric fields (D. Bennett et al., Appl Phys. Lett 2003, 83, 4866; C.D. James et al., J Fluids Eng. 2006, 128, 14). Differences in polarizability between the particle and the fluid leads to body-forces on the particles that enable preconcentration, routing, and transport of particles in fluids. Pairs of microelectrodes coupled to microfluidic channels can then be used for manipulating particles in microfluidic systems for sample preparation and analyte separation. Highly polarizable particles such as bacteria can be efficiently separated form non-polarizable particles such as latex beads of the same size. Also, by placing a DEP gate at the intersection of multiple fluid channels, particles can be routed from one channel to another simply by applying voltage to the DEP gate microelectrodes (C.D. James et al., J Micromech Microeng 2006, 16, 1909).
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Fig. 1: (left) Schematic of the DEP gate across a microfluidic channel. (right) Batch-mode separation of latex beads and bacteria using the DEP gate. |
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Lateral transport can also be accomplished by shifting electric-fields in an array of interdigitated microelectrodes (A. Kumar et al., Appl Phys Lett 2007, 90, 154104). First, particles are preconcentrated at collection zones with a static electric field between microelectrodes. Then, the position of ground vs. high voltage electrodes is shifted, which shifts the collection zone and thus drags the particle aggregates to the next collection zone. This process is repeated in order to achieve full-scale transport.
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Fig. 2: Schematic of particle transport using electric field spatiotemporal shifting. (a) Suspended particles above the electrode field are first (b) preconcentrated into stationary aggregates and then (c) electrode polarities are shifted (red to blue and vice versa) in order to transport the particle aggregates. |
SUMMIT V ™ technology is used to produce multi-level jumpers to connect four sets of microelectrodes together for the “shift-register” configuration required to reduce device complexity.
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Fig. 3: (left) SEM of the multi-level jumpers used to actuate the spatiotemporal shifting electrodes. (right) (a-c) Optical micrographs of particle aggregates during transport. |
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