Microrobots smaller than the width of a human hair have been directed to assemble patterns made of single yeast cells and cell-laden agarose microgels using cavitation bubbles by a team from Hawaii. The robots could be used to push cells together to grow artificial tissue.
There have been a number of different methods used to manipulate single cells into patterns; including micromanipulators, which physically trap and hold cells but need skilled technicians to use them; and optical tweezers, which can be automated but usually need strong lasers or electrical fields that can affect the cells.
Read the full article in Chemistry World.
Or read the Lab on a Chip paper:
Hydrogel microrobots actuated by optically generated vapour bubbles
Wenqi Hu, Kelly S. Ishii, Qihui Fan and Aaron T. Ohta
Lab Chip, 2012,12, 3821-3826