Videos

This video shows how particle trapping increases by increasing the applied DC potential. The microchannel is 10.16 mm long, 2 mm wide and 10 um deep. Post are 440 um in diameter and 520 um center to center, the opening between posts is 80 um.

First only yeast cells are trapped, then by increasing the potential E. coli cells are trapped too closer to the constriction between the cylindrical insulating post. Then we decrease the electric field and we release E. coli cells keeping the yeast cell still trapped, which are released later.

As the potential increases from 0, electrokinetics dominates, and we observe the particles moving through the microchannel. Then, as the magnitude of the applied potential keeps increasing, dielectrophoresis dominates and particles are immobilized. Then, after the maxima, as the potential decreases, electrokinetics dominates again and particles move now in the opposite direction. So we observe cycles of motion-immobilization-motion.

As the potential increases from 0, electrokinetics dominates, and we observe the particles moving through the microchannel. Then dielectrophoretic immobilization occurs and particles form a band, then as the potential decreases, electrokinetic dominates again and particles start to move forward. The cycle repeats and particle form a new band in a new position downstream. It is possible to observe the bands of particle jumping from one row to the next.

The applied potential is a positive sawtooth signal with a peak value of 750 V at a frequency of 0.25 Hz. As the potential increases from 0, electrokinetics dominates, and we observe the particles moving through the microchannel. Then dielectrophoretic immobilization occurs and particles from a band of particles, then as the potential decreases, electrokinetic dominates again and particles start to move forward. The cycle repeats and particle form a new band in a new position downstream. It is possible to observe the bands of particle jumping from one row to the next.

The applied potential is a sinusoidal signal with a peak value of 750 V at a frequency of 1 Hz. As the magnitude of potential increases from zero, particles move due to electrokinetics, then when the magnitude of the potential is high enough particles are immobilized in a band between two rows of posts. Then after the maxima, the potential decreases and electrokinetics dominates again, and particles move, splitting the band of particles, something that we call "the dielectrophoretic dance". This effect was achieved by carefully selecting the frequency of the applied potential.

Live cells are in red color and dead cells are in green color. It can be seen from the videos that the live cells (red) can selectively be trapped while dead cells flow through.