Metal and polymer microgrippers can be guided into place magnetically, then chemically activated within the body. The basic idea is that you will swallow a spoonful of these for microsurgery or biopsies.
The new technology is a step toward surgical tools that move more freely inside the human body. "We want to make mobile surgical tools," says David Gracias, a biomolecular- and chemical-engineering professor at Johns Hopkins University, who led the development of the new gripper. "The ultimate goal is to have a machine that you can swallow, or [to] inject small structures that move and can do things [on their own]."
A gripper based on the current design could respond autonomously to chemical cues in the body. For example, it might react to the biochemicals released by infected tissue by closing around the tissue, so that pieces can be removed for analysis.
Take a look at a microgripper maneuvered magnetically; it then grabs a bead in the following video.
These microgrippers bear an uncomfortable resemblance to the cookie-cutters from Neal Stephenson's 1995 novel The Diamond Age.
Microscopic invaders were more of the threat nowadays. Just to name one example, there was ... the Seven Minute Special, a tiny aerodynamic capsule that burst open on impact and released a thousand or so corpuscle-sized bodies, known colloquially as cookie-cutters, into the victim's bloodstream. It took about seven minutes ... for the cookie cutters to be randomly distributed throughout the victim's organs and limbs.
A cookie-cutter was shaped like an aspirin tablet ... two tiny centrifuges. Detonation dissolved the bonds holding the centrifuges together so that each of a thousand or so ballisticules suddenly flew outward...
(Read more about cookie-cutters)