Trapped cells make micromotors

Researchers working to make machines at the molecular scale are tapping a ready-made source of motors -- biological cells.

In particular, researchers have been experimenting with microorganisms that travel by moving flagella, or long filaments that extend from the cell body.

Researchers from the Tata Institute of Fundamental Research in India have showed that it is possible to make live Chlamydomonas reinhardtii cells rotate while pinned in a laser trap. The energy of a light beam can be used to manipulate and trap cells much like the way wind moves objects a larger scale. Chlamydomonas reinhardtii is a green algae that has an oblong body 7 to 10 microns long. A micron is one thousandth of a millimeter.

The researchers showed that trapping the cells translates the force of the flagella into a rotary motion that spins the organism. The trap probably acts like a frictionless pivot to allow the intrinsic motion of the cell to be converted into a rotary motion, according to the researchers.

The researchers were able to change the cells' rotation direction and stop rotation by altering the pivot point. The cells rotated at 60 to 100 revolutions per minute.

Understanding how cellular motors work promises to pave the way to using the same tricks in microscopic machines. The researchers are aiming to eventually be able to transplant flagella onto any system in order to motorize biological and nonbiological nanodevices.

The ultimate goal is to design controllable motored nanomachines, according to the researchers.

Cell motors could be used practically in five to ten years, according to the researchers. The work appeared in the March 7, 2005 issue of Optics Express (Optically-Controllable, Micron-Sized Motor Based on Live Cells).