An ever-increasing number of research groups are developing tiny robots, capable of performing targeted drug-delivery inside the body. One of the latest such devices incorporates a flapping whale-flukes-like tail, along with wings that fold up or down as needed.

Developed by scientists at Dartmouth College and City University of Hong Kong, the minuscule 3D-printed robot's tail is covered with a layer of cardiomyocytes (heart cells), while its wings are coated with a light-sensitive hydrogel.

As the cells beat in unison (just as they would in the heart) they cause the flexible tail to move up and down. This in turn causes the robot to move forward through a liquid environment, with its extended wings providing lift – they stay extended as long as the device remains in a dark environment.

If the gel on the wings is exposed to skin-penetrating near-infrared light, however, it changes state and causes the wings to curl down. This reduces lift while also creating drag, impeding the device's forward movement and allowing its drug cargo to be released at a given spot.

"The heart muscles keep churning, but they are unable to overcome the stopping power of the wings," says Dartmouth's Asst. Prof. Zi Chen. "It's like pushing the accelerator pedal with the emergency brake on."

In lab tests, the robot has successfully been used to conduct targeted drug delivery against cancer cells. The researchers are now working on a system that will allow them to curl each of the wings individually, increasing the device's maneuverability.

A paper on the project was recently published in the journal Small.