# Algae-Powered Soft Robotic Arms Developed at TU Delft Researchers create bioactuators that use photosynthesis to trigger mechanical movement in hydrogel structures. - **Source:** [Science Latest](https://brifing.si/source/ebc20f22-8d1a-4ae4-ba4c-efcd0853ba19) - **Published:** 2026-11-09 - **Topic:** [science](https://brifing.si/c/science) - **Original article:** - **On Brifing:** https://brifing.si/s/41465642-df6a-444a-8ac1-bc08d7d90340 ## New Bioactuator Technology Researchers at Delft University of Technology have developed soft robotic arms powered by living algae. These bioactuators utilize cellular functions to generate mechanical motion, moving away from traditional metal and wire constructs. The team aims to explore the potential of integrating living biological materials into functional, responsive robotic systems for future applications. ## Hydrogel and Algae Integration The robotic arms measure three-quarters of an inch long and are as thick as a credit card. They are constructed from two hydrogel layers colonized by algae. One layer is specifically designed to respond to pH fluctuations, which are directly mediated by the metabolic processes of the algae living on the surface. ## Photosynthesis Drives Movement When light hits the algae, they photosynthesize, absorbing carbon dioxide and fixing nitrogen, which increases the local pH. This basic environment causes the responsive hydrogel to swell. Conversely, in darkness, respiration releases carbon dioxide, lowering the pH and causing the hydrogel to shrink, effectively controlling the bending motion of the arm. ## Efficiency and Localized Control Unlike previous pH-responsive robots requiring changes to the entire surrounding liquid, these algal bots operate through localized effects. The hydrogel weight fluctuates significantly, shifting from 37 percent of its original weight in acidic conditions to quadruple its weight at pH 11, allowing for precise, environmentally friendly mechanical movement without external chemical inputs. ## Operational Speed and Dexterity While the chemical shift begins within 10 to 20 seconds of light exposure, the hydrogel requires several hours to bend significantly. Despite this slow pace, the arms demonstrate high dexterity. Prototypes include a four-fingered gripper capable of lifting lightweight objects like hollow metal spheres and rubber rings with remarkable precision and control. ## Self-Sustaining Energy Source These robots function without complex mechanical parts or external power sources beyond sunlight. Because microalgae are self-sustaining organisms, the actuators offer potential for long-term operation with minimal external input. This design philosophy reduces the energy requirements for the system, making it a sustainable alternative to traditional, energy-intensive robotic actuators used in industry. ## Safety and Environmental Impact The algae used in these devices do not require genetic modification, eliminating common biosafety concerns associated with microbe-based technologies. These machines are inherently environmentally friendly, as the organisms actively absorb atmospheric carbon dioxide while deriving energy from sunlight. This makes them suitable for applications where minimal environmental impact is a critical design requirement. ## Future Potential Applications The research team envisions these autonomous, environment-responsive robots being utilized in automated agricultural equipment or fluid control for lab-on-a-chip devices. Furthermore, the technology holds promise for underwater robotics systems. By leveraging living materials, the project seeks to push the boundaries of what is possible when biology and engineering are combined. ## Sources covering this story - https://www.wired.com/story/these-robotic-arms-are-made-of-algae-watch-how-they-move/ — --- _Summary written by Brifing from the original reporting. Copyright in the original article belongs to its publisher; read the full piece at the link above._