A research team at Purdue University just unveiled a device which should enhance manipulating entities such as stem cells. Article is published in Journal of Micromechanical
Systems. I have corresponded with Professor Emil Venere and unfortunately copyright restrictions block reproduction of the scientific article but image copy is permitted.
You can obtain an article copy by direct request from Prof Venere.

Purdue Newsroom - New microtweezers may build tiny 'MEMS' structures