Scientists have developed living microrobot swarms made from algae and nanoparticles that can assemble into custom shapes under blue light and disperse on command with red light. The biohybrid system could one day help deliver drugs directly to wounds or diseased tissue using smart bandage-like platforms.

The research team used the green microalga Chlamydomonas reinhardtii to create reconfigurable swarms capable of changing shape, size, and position in real time. By projecting patterned blue light through custom masks, researchers guided the algae into tightly packed formations ranging from stars and arrows to continent-like structures.

Red light reversed the process, causing the swarms to break apart and swim freely again. Researchers say the approach offers a new way to control collective behavior in biohybrid microrobots for medical and environmental applications.

The study also demonstrated an AI-assisted wound treatment concept. Researchers used image-segmentation software to identify suspicious wound regions and generate a matching light mask. The microrobots were then assembled onto medical tape and released directly into the wound area.

Light shapes living swarms

Unlike synthetic microrobots that often rely on magnets or sound waves, the new system uses the algae’s natural light-sensitive behavior. Under blue light, the microorganisms cluster together and migrate toward the liquid-air interface, forming dense swarms. Red light switches them back into a free-swimming state.

The researchers demonstrated reversible swarm formation across multiple cycles with shape fidelity scores above 0.95. The swarms could also split into smaller groups, merge back together, and move while maintaining their geometry.

In one experiment, the team projected masks shaped like the Americas and Afro-Eurasia onto algae-filled dishes. Swarms matching the projected regions formed within minutes. In another test, arrow-shaped swarms traveled several millimeters while preserving their structure.

Researchers also developed a probabilistic algorithm to predict how the swarms behave under changing light conditions. The model simulated how individual algae join or leave clusters depending on irradiation wavelength and intensity.

Smart bandage delivery

To explore medical applications, the team attached drug-carrying PLGA nanoparticles to the algae using electrostatic interactions. The biohybrid microrobots were then tested on simulated wounds created on artificial skin coated with synthetic wound fluid.

An AI image-segmentation system analyzed the wounds and generated custom masks matching inflamed or infected tissue regions. Under blue light, the microrobots assembled on medical tape in the exact geometry of the wound.

After the tape was placed over the target area, red light triggered rapid release of the microrobots. Researchers reported that nearly 90 percent of the biohybrids transferred into the wound cavity in under two minutes.

The team noted that the technology is still limited to surface-level applications because light penetration into tissue remains a challenge. Future work will focus on loading the microrobots with therapeutic drugs and testing them in living systems.

The study was published in the journal Science Advances.