Steering Particles (e.g. cells) by Micro Flow Feedback Control
( vs ABEL trap, we did particle feedback control first.
Details/Documentation )
Students: M.Armani, S.Chaudhary, R.Probst

We precisely control the surrounding fluid to accurately trap and steer multiple particles. If the particle is to the West of its desired
position, we create a flow to move it East, if it is to the North, we
create a correcting South flow. Our control algorithms are sophisticated enough to create correcting flows at multiple locations at once, allowing steering and trapping of one or multiple particles to 1 mm accuracy (this accuracy is set by the resolution of our optical system).

MOVIES

Below we show some movies that demonstrate our capabilities. For details on device fabrication, control algorithms, and capabilities, please see our published journal papers.

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Above: An early experiment, from 2004. Top view of a PDMS device zoomed to where the two channels cross. Two 10 micron beads are visible. The flow is controlled by 4 electrodes (not shown, 1 cm away) to steer one of the beads along the figure 8. The figure 8 is approximately 100 um long. Particle jitter is due to the bead sensing camera-frame 30Hz update rate.

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Above: Theoretical simulation for steering 8 particles at once, to an accuracy of 1 mm.

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Above: Steering of one yeast cell along a UMD path, to an accuracy of 1 mm.

PHOTOS

Above Left: Photograph of the microfluidic devices with the Cursive “UMD” path super-imposed on the image. The four control electrodes are located outside figure frame.

Above Right: The actual path of the yeast cell (white dot) in the feedback control experiment. The yeast cell is being steered to an accuracy of one micron. Any other cell that is small enough to act as a particle in the flow could also be steered in this way: the type of cell is not important from a flow control perspective.

Steering 4 particles at once (top view): grey disks = electrodes; color field = electric potential; arrows = electric field; black circles = particles to be steered; black curves = actual particles paths (match desired paths).

Experimental results for steering three yeast cells to one micron accuracy by electroosmotic flow control

Left: PDMS microfluidic device with 8 control electrodes (one in each of the lightbulb shaped reservoirs). Right: Steering of 3 cells at once along two circles and a UMD path by electroosmotic flow control. White traces shows path of the cells, arrows show current cell locations. Can also trap 1 or 2 cells while steering the others.