There's tiny revolution afoot in medicine, where micro- and nano-sized robots will someday cruise around inside our bodies, zeroing in on cancerous cells or repairing damaged but otherwise healthy ones. But before those ideas all become reality, those bots need a power source inside our bodies. That power source could be stomach acid.

Scientists at the University of California, San Diego have created micro missiles that fire inside the stomachs of mice. As New Scientist reports, the 20 micrometer-long polymer tubes were coated in zinc, which reacts with stomach acid to form hydrogen bubbles. That gives it enough power to lodge into the stomach lining of mice, depositing its payload of gold nanoparticles. This is the first time a self-propelled machine has been tested in a living animal rather than cells in a petri dish.


The gold nanoparticles proved that the zinc-stomach acid system could be used to deliver chemicals straight into the stomach lining. And the "chemicals" we're interested in, of course, are drugs, especially ones that otherwise have to be injected through needles rather than swallowed.

The field of tiny robots in medicine has bloomed in recent years. There's DNA-based nanobots that essentially turn the cockroach they're injected inside into 8-bit computers. And microspiders that could crawl around repairing blood vessels. And magnetically controlled nanopropellors. The zinc-acid system obviously won't work in all these cases, but it is a promising step forward for tiny machines designed to work in the stomach. There's a lot of wild promises out there for nanobots in medicine, some that might even work. [New Scientist]