Algae Power Micromachines for Research and Engineering

Scientists have built little, vehicle-like structures that microscopic algae can drive. The micromachines have baskets attached to them that catch the algae and are thoughtfully made to provide them adequate space to swim around in.

Two other kinds of vehicles were developed: the “scooter,” which was meant to travel forward but moved more unexpectedly in tests, and the “rotator,” which spins like a wheel.

For its upcoming cars, the team intends to experiment with various and intricate designs. These miniature algal teams may be used in the future to support environmental research and engineering at the microscale.

Most people are aware of horsepower, but what about the power of algae? Researchers have developed small, living, single-celled green algae that can drive minuscule machinery, much like a plow pulled by oxen or a sled towed by a pack of dogs.

We were inspired to try and harness Chlamydomonas reinhardtii, a very common algae found all over the world, after being impressed by its swift and unrestricted swimming capabilities. We have now shown that these algae can be trapped without impairing their mobility, offering a new option for propelling micromachines which could be used for engineering or research purposes."

Naoto Shimizu, Student, Graduate School of Information Science and Technology, University of Tokyo

Two-photon stereolithography, a 3D printing technique, was used to build the micromachines. This printer turns plastic into microstructures by using light. The group operated on a 1 mm scale, which is equivalent to 0.001 mm.

The hardest element, according to the researchers, was perfecting the basket-shaped trap's design to ensure that the algae could be successfully captured and held inside when they swam into it.

Attached to two distinct micromachines were the traps. The first, dubbed the scooter, resembles a Star Wars podracer and includes two traps with algae inside of each. The second, known as the rotator, resembles a Ferris wheel and includes four traps that can store a total of four algae.

The alga's two flagella, which are tiny, whip-like appendages, were able to continue moving due to the size and structure of the baskets, which helped the machines move forward.

As we had hoped, the rotator displayed a smooth rotational movement. However, we were surprised by the scooter. We thought it would move in one direction, as the algae face the same way. Instead, we observed a range of erratic rolling and flipping motions. This has prompted us to further investigate how the collective movement of multiple algae influences the motion of the micromachine."

Haruka Oda, Study Lead Author and Project Research Associate, Graduate School of Information Science and Technology

The primary benefit of these micromachines over those powered by other creatures, in the opinion of the researchers, is that neither the machine nor the algae need any chemical alteration.

Furthermore, the algae can enter the trap without the assistance of outside structures. This facilitates increased mobility for the micromachine and streamlines the procedure.

How long these micro-chariots and their small steeds can endure and keep working is still unknown. Chlamydomonas reinhardtii can replicate to form four new algae within a two-day period. The micromachines remained in their form for the duration of the experiments, which lasted for several hours.

The group's next goals are to make the rotator spin more quickly and design new, intricate machinery.

The methods developed here are not only useful for visualizing the individual movements of algae but also for developing a tool that can analyze their coordinated movements under constrained conditions. These methods have the potential to evolve in the future into a technology that can be used for environmental monitoring in aquatic environments, and for substance transport using microorganisms, such as moving pollutants or nutrients in water."

Shoji Takeuchi, Project Supervisor, Graduate School of Information Science and Technology