Scientists have created a tiny biobot that can be implanted under the skin and deliver doses of drugs. The 3D-printed micromachine has no batteries or wires, but is activated through an external magnet. It’s only been tested in mice for now, but it could one day be used to deliver localized doses of chemo to treat tumors.

The biobot, described in a study published yesterday in the journal Science Robotics, is made of hydrogel, a solid jelly-like material that makes the machine soft but resistant. It has a Geneva drive, the same gear mechanism used in watches to make seconds tick. In this hydrogel biobot, the Geneva drive is activated by an external magnet; the rotation allows one of six tiny chambers filled with drugs to line up with a hole and release a dose.

The mechanism in action can be observed in this video:

The idea is that, when implanted under the skin in the tumor’s area, a doctor could simply use an outside magnet to move the gear and deliver the drug when needed. The whole mechanism, which is only 0.6 inches long, took only 30 minutes to 3D print.

The researchers tested the device for 10 days in mice with bone cancer, and compared the results with mice that received a typical chemotherapy treatment. The biobots were loaded with the chemo drug doxorubicin and implanted under the mice’s skin. These mice had less tumor growth and fewer damaged cells in other organs than the mice that received the standard chemo treatment, which floods the whole body with the chemo drug and can be toxic.

The research on these soft miniaturized robots is only at the beginning, but they look promising. In the future, they could be adapted to meet the needs of individual patients and treat tumors, as well as other conditions.