In 1959, the famous theoretical physicist Richard Feynman fantasized about a future in which microrobots swim in our blood, fix our insides or deliver medicine as they go.
Sixty-five years later, scientists are getting closer to that reality.
Engineers at the University of Tokyo have already devised a way to motorize 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 small horses.
The research was not simply a pursuit of attractiveness, although it looks as fascinating as it sounds. One of the problems with the “microbots” designed so far is that because they are so small, liquids like blood can take on the viscosity of molasses.
This makes it difficult for the bot to move, which is why scientists have been trying for years to create small motors powerful enough to propel such structures with greater ease.
Using the fast swimming abilities of green algae Chlamydomonas reinhardtiiengineers in Japan have come up with a unique solution.
Each cell of C. reinhardtii is only 10 micrometers wide, which is one-third the size of the tugboat Benchy, the world’s smallest 3D-printed ship in 2020.
Together, however, they can pull machines five times their own individual size — “opening up a whole new realm of possibilities for developing complex micromachines,” say the machine’s designers.
The kelp, which is considered safe for human consumption, is powered by two flagella, propelling each unit forward in a beam-like manner.
Trapped in a specially designed bridle-like basket, the cage’s whips protrude from the front, allowing it to drag the rest of the vehicle behind it as it paddles.
Unlike other micromotors that scientists have designed—which often rely on external power sources such as magnetic or electric fields—living motors such as C. reinhardtii can move autonomously.
Lead author Haruka Oda and his colleagues designed two different, 3D-printed plastic algae management vehicles, each measuring between 50 to 60 microns in width. To put it into perspective, the average human hair is about 100 microns thick.
One of the micro machines is called “Scooter”. There are two baskets to catch two cells of algae, both facing the same direction and connected by a “carriage” at the back.
without prompting C. reinhardtii take their positions in each cockpit.
The researchers were surprised to find that the scooter did not move straight even when each basket was occupied. Instead, it twisted and turned in complex ways. Even did 15 back flips and 10 rolling moves.
The other vehicle form, called the Rotator, moved more smoothly. It is designed with four baskets, all of which point in the same direction and are connected by spokes in a wheel-like formation.
With one algae cell occupying each of the four baskets, the structure “spins” at an average speed of 20 to 40 micrometers per second, sort of like a microscopic carnival ride.
° С. reinhardtii it can reach speeds of 100 micrometers per second when unencumbered, so researchers are now trying to see if they can make these micromachines move faster and with greater precision.
The rotator, which was just 56 micrometers in size, is five times larger than another previously designed microcar made in 2017 to be powered by self-propelled bacteria. Unlike algae, however, the speed of these bacteria had to be controlled by a special light modulator.
“The methods developed here are useful not only for visualizing the individual movements of algae, but also for developing a tool that can analyze their coordinated movements under limited conditions,” says Shoji Takeuchi, who led the project.
“These methods have the potential to be developed in the future into technology that can be used for environmental monitoring in aquatic environments and for the transport of substances using microorganisms, such as moving pollutants or nutrients in water.”
One day, these lines of research might even lead to Feynman’s dream of a microbot delivering a “small cargo,” like medicine, in a liquid medium, like blood, powered by life itself.
The study was published in small.
