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Scientists create working, ‘swarming’ microrobots

The vanishingly tiny robots could find use in delivering drugs to specific sites in the body or detecting pathogens.

(CN) — Researchers have successfully created molecular robots capable of swarming together to accomplish tasks together about five times more efficiently than individual “microrobots” could.

At six micrometers in length and 25 nanometers in diameter, each of these robots is invisible to the human eye. But with a design combining robotics and biological engineering, scientists were able to make 5 million of these molecular robots work together to deliver beads of polystyrene, the polymer perhaps best known for its use as Styrofoam and in packing peanuts.

“After swarm formation, those 5 million robots move in parallel as a bundle,” wrote Hokkaido University scientists Mousumi Akter and Akira Kakugo in a joint email interview with Courthouse News. “They are so tiny that it is only possible to observe under a microscope.”

In new research published Wednesday in the peer-reviewed journal Science Robotics, Akter, Kakugo and four of their colleagues detail how they built the machines from microtubules with DNA attached to them and kinesin, a motor protein that acted as an actuator that could transport the microtubules.

The microtubules were the key to controlling the tiny bots, as the DNA attached to them was photoreceptive in nature.

“In these molecular robots, microtubules were modified with azobenzene incorporated single-stranded DNA by azide-alkyne cycloaddition reaction. Azobenzene, a photosensor, was incorporated into the DNA strands to regulate their duplex formation by changing their melting temperature through cis-trans isomerization,” Akter and Kakugo explained.

When the microrobots were exposed to visible light, they would begin to swarm. Ultraviolet rays would dissipate the swarm.

“Swarming of these robots was initiated by DNA duplex formation which was induced by the trans isomerization of the azobenzene units in the single-stranded DNA under [visible] light irradiation. UV light irradiation induces the dissociation of the swarming of these robots,” Akter and Kakugo continued.

Light is not the only plausible way of controlling the robot swarm, however. Akter and Kakugo mentioned a previous study they worked together on, in which external chemical signals stored in DNA chains could also control a swarm of microrobots “in a reversible manner.”

In the study’s experiments, the swarming microrobots could load, transport and unload beads of polystyrene. Though individual bots could only move beads as large as 3 micrometers in diameter, the swarm could together transport beads 10 times as large.

The accomplishment is a proof of concept for other applications these tiny robots could be put to.

“Intensive drug delivery to a specific location or collection of micro-contaminants from environments is the most possible application,” wrote Akter and Kakugo. “Compared to electric machines, the output efficiency of biological molecular machines is a thousand times higher, which makes them fascinating for future applications. … We also expect our swarm of molecular machines will be useful for a micro-device that can detect pathogen or genetic information or as micro-reactors by assembling nano-parts together in a more efficient way.”

The pair also said they want to imbue future robots with artificial intelligence to further expand their usefulness.

“It is one of our goals to make the molecular robots smarter and more active for complex task achievement by implementing artificial intelligence in them,” Kakugo and Akter noted.

They suggested that a swarm of artificially intelligent molecular robots could “behave as tiny millimeter-sized flies.”

“Being a tiny natural machine, a fly can continue [a] thousand complex tasks together; our plan is to add more powerful sensing systems to our molecular robots to grow their strong eyesight,” the scientists wrote.

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