Dielectrophoretic Sorting of Particles and Cells in a Microsystem

Abstract

There are highly sensitive analytical techniques for probing cellular and molecular events in very small volumes. The development of microtools for effective sample handling and separation in such volumes remains a challenge. Most devices developed so far use electrophoretic and chromatographic separation methods. We show that forces generated by ac fields under conditions of negative dielectrophoresis (DEP) can also be used. Miniaturized electrode arrays are housed in a microchannel and driven with high-frequency ac. A laminar liquid flow carries particles past the electrodes. Modification of the ac drive changes the particle trajectories. We have handled latex particles of micrometer size and living mammalian cells in a device which consists of the following four elements: a planar funnel which concentrates particles from a 1-mm-wide stream to a beam of about 50-micron width, an aligner which narrows the beam further and acts to break up particle aggregates, a field cage which can be used to trap particles, and a switch which can direct particles into one of two output channels. The electrodes are made from platinum/titanium and indium tin oxide (ITO) on glass substrates. Particle concentration and switching could be achieved for linear flow velocities up to about 10 mm s-1. The combination of this new method with high-performance optical detection offers prospects for miniaturized flow cytometry.

Determination of pathogenic bacteria by CZE with surface‐modified capillaries

“…Unfortunately, the same situation in medical diagnosis of pathogenic bacteria is observed because traditional colony counts methods are always slow (up to 72 h). Obviously, there are some new technologies such as: PCR detection [2], flow cytometry [3,4], differential staining [5], serological methods and recently dielectrophoresis [6][7][8][9][10][11][12][13][14][15][16][17], or microchipbased technology [18]. For instance, PCR method is extremely sensitive, however requires pure samples and hours of analysis and expertise in molecular biology.…”

3D focusing of nanoparticles in microfluidic channels

“…It has been shown that particles can be focused in three dimensions using electric field cages, and also in twodimensions within a fluid stream [11][12][13]. A small channel, typically 50 mm across is microfabricated with pairs of electrodes on the top and bottom.…”

“…A small channel, typically 50 mm across is microfabricated with pairs of electrodes on the top and bottom. Using negative dielectrophoresis, particles are repelled from the electrode edges and form a tight beam in the channel centre [11,12].…”

“…As has been shown [11][12][13], it is relatively easy to focus or trap large particles such as cells in microchannels using relatively low voltages. However, in order to achieve effective focusing of nanoparticles, the magnitude of the DEP force, i.e.…”

“…DEP has already successfully been employed to the manipulation of micro-and nanoparticles, for cell sorting and separation [9][10][11][12][13][14][15][16][17] single cell characterisation [15,[18][19][20] …”