Delft researchers build light-controlled soft actuator powered by algae

Researchers at Delft University of Technology have developed a proof-of-concept soft robotic actuator that uses living microalgae to convert light-driven metabolism into reversible bending, underwater grasping and object lifting. The experimental device is a green, flexible strip about 2 centimeters long and 1 millimeter thick, formed from two different hydrogel layers with microalgae growing on its surface. Demonstrated in an aquatic setting, the strip hooked and lifted a rubber ring and grasped a small metal ball, according to the researchers’ report in Nature Communications .

The bending mechanism begins with the microorganisms’ metabolism. Under illumination, the algae use light energy and carbon dioxide to make sugars through photosynthesis while also using nitrogen to build cellular components. Together, these processes increase the pH inside the hydrogels.

Because the two layers respond differently to pH changes, they swell to different degrees, forcing the strip to curve. When the light is switched off, the algae use or “burn” their stored cellular fuel and release carbon dioxide, shifting the pH back down. Within 10 seconds, the actuator begins bending in the opposite direction.

The experiments therefore demonstrate a light-responsive, reversible mechanical response rather than a one-time deformation. Lead researcher Marie-Eve Aubin-Tam described the actuator as a proof-of-concept living-material strip whose shape can be modified to produce different movements and functions. The researchers used its bending action for simple underwater manipulation tasks, including lifting a rubber ring and holding a small metal ball.

They do show, however, that photosynthetic organisms can serve as the biological control layer in a soft material that translates metabolic activity into movement, including the manipulation of discrete objects. The project was not designed around a single predetermined application. “We didn’t start with a specific application,” Aubin-Tam said.

“Our goal has always been to bring the research of living materials to new levels. We wanted to explore what becomes possible when living cells are integrated into functional materials.” The team also said its light-controlled bending could eventually be incorporated into blinds or agricultural devices that change shape or orientation in response to light. Those examples are proposed directions for development, not tested products in the reported study.

More broadly, the work offers a platform for investigating soft robotic and biomimetic functions that resemble movements found in nature. Microalgae may also provide a route to soft robotic systems that are relatively autonomous and environmentally responsive. The organisms are plantlike and largely self-sustaining, obtaining energy through photosynthesis.

In principle, an actuator based on this biological process could operate with minimal external energy and for extended periods, the researchers said. The release did not report a measured operating lifetime or energy consumption, so those longer-term possibilities remain unverified. Aubin-Tam nevertheless said the experiment was compelling because it directly visualized metabolism in microorganisms being translated into mechanical motion: “To see synthetic materials actually translate the algae’s biological responses into mechanical motion.” First author Fan Jiang and the team reported the algae-coated hydrogel actuator, its reversible bending and its underwater manipulation demonstrations in the experimental study.

Subject of Research: Experimental development of a light-controlled, microalgae-powered soft robotic actuator

Article Title: A soft robot arm powered by algae and light

Article References: A soft robot arm powered by algae and light. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: soft robotics, microalgae, light control, biohybrid materials, hydrogel actuator, photosynthesis, underwater robotics, biomimetics, living materials, Delft University of Technology, soft, robot