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Microrobots move cells

Tiny tools powered by optoelectronic tweezers manipulate targets

by Celia Henry Arnaud
July 12, 2019 | A version of this story appeared in Volume 97, Issue 28


Micrograph of an array of cogwheel-shaped microrobots.
Credit: Proc. Natl. Acad. Sci. U.S.A.
These cogwheel-shaped microrobots, each of which is about 200 µm wide, can pick up and transport cells.

Microrobots can help manipulate objects too small or delicate for humans to grasp, but the robots themselves must be controlled with dexterity. Aaron R. Wheeler of the University of Toronto and coworkers have now shown that optoelectronic tweezers (OET) can be used to control microrobots of various shapes (Proc. Natl. Acad. Sci. U.S.A. 2019, DOI: 10.1073/pnas.1903406116). Shining light on a photosensitive substrate in OET generates virtual electrodes that produce a nonuniform electric field. The electric field can exert a force via the so-called dielectrophoretic effect and manipulate tiny objects, such as the microrobots. The force produced by OET is stronger than forces produced by conventional optical tweezers. OET is typically used to directly manipulate objects of interest. But using the robots as mediators is faster and less damaging to fragile objects, such as cells, than direct OET. Using the indirect approach, the researchers were able to maneuver the robots around obstacles, such as cellular debris. They used the robots to isolate and transport cells, fuse them, and subject them to RNA sequencing. Such robots “will be particularly useful for transporting objects that are hard to move by exerting force directly,” says Ming C. Wu of the University of California, Berkeley, the inventor of OET.


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