Algae-powered robot arms that move with light

Soft robots that bend like muscle

Soft actuators convert energy into mechanical motion and flex like a bicep with fine-tuned touch. They could power artificial muscles and wearable devices where delicate handling matters.

Living cells power the movement

Bioactuators use living cells to generate motion. Delft University of Technology in the Netherlands built soft robotic arms colonized by algae that move when the microbes photosynthesize.

How the algae make arms bend

The arms are three-quarters of an inch long, made of two hydrogel layers. When algae photosynthesize in light, they make the pH more basic and one layer swells. Darkness reverses this, making it shrink.

The pH shift is dramatic

In acidic conditions between pH three and seven, the responsive hydrogel layer was approximately thirty-seven percent of its original weight. At pH eleven it quadrupled its original weight.

Slow but steady movement

The chemical shift begins about twenty seconds after light is applied and about ten seconds after it becomes dark. But it takes several hours for the hydrogel to bend significantly.

Grippers that lift and release

A four-fingered gripper closes when exposed to light and successfully grasped and lifted a hollow metal sphere, releasing it when light turned off. Another hook-shaped gripper picked up and put down a rubber ring.

No external power needed

The robots require only light and no complex mechanical parts. Microalgae are largely self-sustaining, giving the actuator potential for long-term operation with minimal external input and no genetic modification needed.

“Microalgae are plantlike organisms that are largely self-sustaining.”