MIT researchers have found a way to use the technology of optical tweezers to pick up, hold, and move around individual cells and other objects on the surface of a microchip. The development could become an important tool for both biological research and materials research, say MIT researchers Matthew J. Lang and David C. Appleyard.

Optical tweezers use the tiny force of a beam of light from a laser to push around and control tiny objects, from cells to plastic beads. They usually work on a glass surface mounted inside a microscope, so that the effects can be observed.

But because silicon chips are opaque to light, applying this technique to them not an obvious move, the researchers say, since the optical tweezers use light beams that have to travel through the material to reach the working surface. The scientists successfully selected optical tweezers suited for various cells and tiny beads, and were able to manipulate a square with a hollow center that was 20 micrometers, or millionths of a meter, across. This demonstrated that even larger objects could be moved and rotated.

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