Micro-manipulation in action

We've previously reported on the use of light patterning techniques to manipulate the movement of particles in solution (Microscopic particle manipulation for screening operations), but now the method has been improved upon and we can see it in action.

The latest work improves on the conventional optoelectronic tweezers by using phototransistors instead of amorphous silicon photoconductors, which makes the technique better suited to biological applications involving living cells¹.

Particles suspended in solution are placed on a grid of discrete phototransistors. When the light pattern approaches a cell it gives the appearance of repelling it. What is actually happening is that the light is activating the phototransistors beneath it, generating a localised electric field which then influences the movement of the cell.

In an online article for New Scientist, Colin Barras describes the "high-tech Petri dish" and provides the following video footage²:

The dynamic light patterns were produced by a laser illuminated spatial light modulator, which could be programmed to corral scattered particles into a group, isolate individual particles, or arrange multiple particles into arrays. Such a tool could produce great advances in the biological sciences, studying the behaviour and interaction of living cells, guiding them without touch like some unseen hand.