Such robots would have a long and challenging list of requirements. For example, they would need to survive in bodily fluids, such as stomach acids, and be controllable, so they could be directed precisely to targeted sites. They also must release their medical cargo only when they reach their target, and then be absorbable by the body without causing harm.

Now, microrobots that tick all those boxes have been developed by a Caltech-led team. Using the bots, the team successfully delivered therapeutics that decreased the size of bladder tumors in mice.

A paper describing the work titled "Imaging-guided bioresorbable acoustic hydrogel microrobots" appears in the journal Science Robotics.

"We have designed a single platform that can address all of these problems," says Wei Gao, professor of medical engineering at Caltech, Heritage Medical Research Institute Investigator, and co-corresponding author of the new paper about the bots, which the team calls bioresorbable acoustic microrobots (BAM).

"Rather than putting a drug into the body and letting it diffuse everywhere, now we can guide our microrobots directly to a tumor site and release the drug in a controlled and efficient way," Gao says.