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Hot off the Press: Optoelectronic Tweezers

by PhilipJ on 22 July 2005

In today’s Nature, a new high throughput method for manipulating micrometer-scale particles is introduced, called optoelectronic tweezers (OETs)!

Current techniques can give you either high throughput or high resolution in terms of particle manipulation: optical tweezers have very high resolution (from single particles in conventional optical tweezers to a couple of hundred particles in the more recently developed Dynamic Holographic Optical Tweezers, while electrokinetic (electrophoresis, dielectrophoresis, etc) techinques are high throughput but you lose the ability to manipulate individual particles.

In OETs, liquid containing microscopic particles of interest is sandwiched between indium-tin-oxide glass (ITO) on the top and a photosensitive ITO-coated glass topped with amorphous hydrogenated silicon layers on the bottom. Through the use of a spatial light modulator, images (from an inexpensive incoherent light source) of any desire can be imprinted onto the bottom photosensitive glass layer, leading to dynamic optically-induced dielectrophoretic forces on the objects sandwhiched between the glass. Up to 15,000 traps were generated in a 1.3×1.0 square millimeter area!

Particularly cool are the movies in the supplemental information section showing the optoelectronic tweezers in action, examples of which are a B-cell concentrator and an integrated optical manipulator (subscription required to view movies).

The full text, also requiring a subscription, is here.

  1. André    4295 days ago    #
    Hi Phil,

    Those movies are awesome! I was going to link this to a talk I saw at BioImage by W.E. Moerner from Stanford about an electric trap, but clearly from the movies this is quite a seperate development.

    His trap does have the interesting feature though that, unlike an optical trap, it actually tends to reject non-trapped particles so that you don’t get a build up of several particles over time if you run an experiment at high concentrations. (Although you do sometimes see an exchange of the particle in the trap with one from solution.)

    Here’s the link to their electrophoretic trapping site:
  2. PhilipJ    4294 days ago    #
    Hey Andre,
    In my lab’s optical trap, we fortunately don’t get any clumping together of trapped particles (unless the beads themselves are stuck together, which does seem to happen sometimes), but we do experience the exchange of particles in a trap. When a bead wanders near an already trapped bead, sometimes you can see it get pulled in to the centre quite quickly, presumably knocking the bead that was trapped out, and taking its place.

    The electrophoretic trap you link to is also cool! I remember seeing the paper in PRL and its associated Focus article. It is quite remarkable how many new techniques are being developed to manipulate mesoscale matter. Hopefully interesting science results will soon follow!

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