Algae instead of motors: Delft soft robot arm grips using light and photosynthesis
Researchers at Delft University of Technology have built a soft gripper just two centimeters long that is powered by living microalgae. It bends in light and can hold tiny objects.
Symbolic image · Photo: Dartmouth Electron Microscope Facility, Dartmouth College / Wikimedia Commons, Public domain (cropped and resized)
Researchers at Delft University of Technology in the Netherlands have developed a soft robot arm that needs neither a motor nor a battery and is instead powered by green algae and light. The strip, made of two hydrogel layers, is about two centimeters long and one millimeter thick, with a layer of the freshwater alga Chlamydomonas reinhardtii growing on its surface. The algae are not genetically modified. The work was published in the journal Nature Communications.
Under illumination, the algae carry out photosynthesis and raise the pH inside the gel. The two layers respond differently to pH and swell to different degrees, causing the strip to curl. In the dark, the algae's respiration releases carbon dioxide, the pH drops and the arm bends back. "Within 10 seconds the actuator already starts bending in the opposite direction," first author Fan Jiang said, according to TU Delft.
In tests, the arm hooked a small rubber ring and, configured as a four-finger gripper, closed around a tiny metal ball that it released in the dark. The forces are very small, however, a full bend can take up to 18 hours according to t3n, and the system only works in nutrient-rich liquid. Lead researcher Marie-Eve Aubin-Tam sees possible uses in light-controlled shading elements and agriculture.