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(Color online) Micrograph and schematic diagram of the micropost matrix. (a) Micrograph of the micropost matrix. The tops of the posts are in the focal plane, the electrical leads are below the focal plane, and the insulating SU-8 is transparent. (b) Three-dimensional drawing showing the design of the micropost matrix. (c) Cross-sectional schematic of the device. The micropost matrix is composed of gold leads with high post shaped electrodes on top of them. The array of electrodes is capped with a thick insulating layer. The insulating layer forms the bottom of a high fluidic chamber that is sealed with a conductive coverslip.
(Color) Electric-field simulations of trapping fields created by the micropost matrix. (a) Electric-field pattern in a plane located above the top of the posts showing a minimum for nDEP trapping. (b) Electric-field pattern in a plane located above the top of the posts showing a maximum for pDEP trapping. (c) Cross section of the field pattern along the dotted line in (a). (d) Cross section of the field along the dotted line in (b). The actual geometry of the device is outlined in the figure, including the location of the leads and a cross section of the posts.
(Color online) Trapping and manipulation of a single yeast cell with pDEP. (a) A yeast cell (circled, contrast enhanced) is translated clockwise in a square pattern above the micropost matrix. The post shaped electrodes, in diameter, are spaced center to center. (b) Electric-field simulations of the trapping field acting on the yeast cell in each location. The yeast is pulled into the maximum of the electric field. The simulation plane is above the bottom of the chamber, close to the center of the trapped yeast cell. Arrows indicate direction of trap motion. The locations of energized micropost electrodes are circled in white; grounded electrodes are circled in dotted white.
(Color online) Trapping and manipulation of a single diameter polystyrene bead with nDEP. (a) The trapped bead (circled by dotted line, contrast enhanced) follows the minimum of the electric field created by the micropost matrix. (b) Simulation of the field inside the microfluidic channel in a plane located above the top of the microposts. The field minimum is produced between the grounded conductive coverslip and the grounded micropost electrodes (location circled in white) surrounded by energized micropost electrodes (location circled in gray). The trap was moved above the matrix by selectively energizing or grounding the microposts. Arrows indicate the direction of trap motion.
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