science

One way to manipulate tiny particles like single cells is to trap and move them using light, which has enough energy to act like a wind at very small scales.

Researchers from the University of Glasgow in Scotland and the University of Oxford in England have devised a way to use hologram patterns to shape the intensity of different portions of a light beam so that several different particles can be simultaneously trapped and individually controlled in three dimensions.

The researchers devised an algorithm that works quickly enough to control the light beam interactively with a keyboard and mouse. The algorithm repeatedly refines the hologram pattern so that moving, adding and deleting individual light traps does not require recalculating the hologram as a whole. This makes it possible to control the light beam in real-time.

Optical tweezers are already used as tools to, for example, hold the ends of a muscle cell and measure its exertion force. More sophisticated optical tweezers that offer better three-dimensional control of tiny objects could drive pistons and valves to power labs-on-a-chip.

The hologram generator could be added to existing commercial optical tweezers relatively easily, according to the researchers. The work appeared in the April 19, 2004 issue of Optics Express.

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