A small robotic arm capable of grasping objects underwater thanks to algae. It is the result of research at Delft University of Technology in the Netherlands, which combines living cells and synthetic materials to transform light into movement.

The team, led by researcher Marie-Eve Aubin-Tam, has developed a flexible strip approximately two centimeters long and one millimeter thick. It consists of two layers of hydrogel, a material containing abundant water, and microalgae growing on its surface. The work has been published in Nature Communications .

How does it move? When exposed to light, the microalgae perform photosynthesis and, along with other metabolic processes, modify the pH, which indicates the acidity of the environment. The two layers respond differently: they swell to varying degrees, and the strip curves. In darkness, the algae release carbon dioxide as they consume stored sugars. The pH decreases, and the movement reverses. Thus, the activity of these microorganisms becomes a mechanical action that can be repeated.

To demonstrate this, the researchers used the device to lift a rubber ring and grasp a small metal sphere. Although the response begins within seconds, the complete movements are slow: the videos released by the university are sped up. This is a proof of concept, still far from everyday application.

The research opens up possibilities for developing soft robots that respond to their environment and harness light as an energy source. Among the potential applications, the team envisions devices for manipulating delicate objects underwater, shading systems, and agricultural tools that change shape according to lighting conditions. For now, the breakthrough demonstrates how to integrate living organisms into materials capable of performing simple tasks through light-controlled biological processes.

A soft robotic arm covered in algae, placed in a specially designed aquarium. Credits: Studio Oostrum

Source: https://www.nature.com/articles/s41467-026-78653-z?utm_source