These Tiny Vehicles Are Driven By Something You’d Never Guess: ScienceAlert

In 1959, the famous theoretical physicist Richard Feynman fantasized about a future in which microrobots swam through our bloodstreams, repairing our internal organs or delivering drugs as they went.

Sixty-five years later, scientists are getting closer to that reality.

Engineers at the University of Tokyo have now discovered a way to power tiny microscopic structures without the need for an external power source.

The solution? A team of free-moving single-celled organisms, harnessed to a “chariot” like tiny horses.

The research wasn’t just about making things cuter, although they are as adorable as they look. One problem with the “microbots” designed so far is that being so small, fluids like blood can take on the viscosity of molasses.

This makes it more difficult for the robot to move, which is why scientists have been trying for years to create tiny motors powerful enough to propel such structures more easily.

Harnessing the fast swimming capabilities of green algae Chlamydomonas reinhardtiiJapanese engineers have developed a unique solution.

Each cell of C. reinhardtii is just 10 micrometers wide, a third of the size of the tugboat Benchy – the world’s smallest ship, 3D printed in 2020.

Together, however, they can pull machines five times larger than their own individual size – “opening up a whole new realm of possibilities for the development of complex micromachines,” the machine’s designers say.

Algae, considered fit for human consumption, are propelled by two flagella, propelling each unit forward in a manner similar to the breaststroke.

Trapped inside a specially designed flange-like basket, the cell’s flagella protrude forward, allowing it to drag the rest of the vehicle behind it as it paddles.

Unlike other micromotors designed by scientists – which often rely on external energy sources like magnetic or electric fields – living motors like C. reinhardtii can move independently.

Lead author Haruka Oda and colleagues designed two 3D-printed plastic vehicles for the algae to navigate, each measuring between 50 and 60 microns wide. To put that in perspective, an average human hair is about 100 microns thick.

One of the micromachines is called the “Scooter.” It has two baskets designed to trap two algae cells, both facing the same direction and connected to a “trolley” at the back.

Without being invited, C. reinhardtii take up position in each cockpit.

The researchers were surprised to find that the scooter did not move in a straight line, even when each basket was occupied. Instead, it twisted and turned in complex ways. It even performed 15 backflips and 10 rolls.

The other form of vehicle, called a “Rotator,” moved more smoothly. It was designed with four baskets, all facing the same direction and connected by spokes to form a wheel.

With one algal cell occupying each of the four baskets, the structure “spins” at an average speed of 20 to 40 micrometers per second, much like a ride at a microscopic funfair.

vs. reinhardtii can reach speeds of 100 micrometers per second when unobstructed. So researchers are now trying to see if they can make these micromachines move faster and more precisely.

The Rotator, which measures just 56 micrometers, is five times larger than another microvehicle previously designed in 2017 to be powered by self-propelled bacteria. But unlike algae, the speed of these bacteria must be controlled by a special light modulator.

“The methods developed here are not only useful for visualizing individual algae movements, but also for developing a tool capable of analyzing their coordinated movements under constrained conditions,” says Shoji Takeuchi, who supervised the project.

“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 the transport of substances using microorganisms, such as the movement of pollutants or nutrients in water.”

One day, these lines of research might even give rise to Feynman’s dream of a microbot delivering “small cargo,” such as medicine, in a liquid environment, such as blood, fueled by life itself.

The study was published in Little.