But now, a new device developed by University of California, Berkeley, engineers, and dubbed an "optoelectronic tweezer," will enable researchers to easily manipulate large numbers of single cells and particles using optical images projected onto a glass slide coated with photoconductive materials.

"This is the first time a single light-emitting diode has been used to trap more than 10,000 microparticles at the same time," said Ming Wu, UC Berkeley professor of electrical engineering and computer sciences and principal investigator of the study. "Optoelectronic tweezers can produce instant microfluidic circuits without the need for sophisticated microfabrication techniques."

This technique, reported in the July 21 issue of the journal Nature, has an advantage over existing methods of manipulating cells, such as optical tweezers that use focused laser beams to "trap" small molecules. Such techniques require high-powered lasers, and their tight focusing requirements fundamentally limit the number of cells that can be moved at the same time.

Wu and his UC Berkeley graduate students, Pei Yu Chiou and Aaron Ohta, also improved upon other cell manipulation tools that use electrokinetic forces to create electric fields that either repel or attract particles in order to move them. Dielectrophoresis, for instance, can move larger numbers of particles. However, it lacks the resolution and flexibility of optical tweezers.

The UC Berkeley engineers found a way to get the best of both worlds by transforming optical energy to electrical energy through the use of a photoconductive surface. The idea is similar to that used in the ubiquitous office copier machine. In xerography, a document is scanned and transferred onto a photosensit
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Contact: Sarah Yang
scyang@berkeley.edu
510-643-7741
University of California - Berkeley
20-Jul-2005