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Chemistry often conjures images of mixing fluids together in beakers, flasks, or test tubes. But often, chemistry happens on a much smaller scale. In many medical and industrial contexts, mixing fluids involves fractions of a milliliter, and for these applications, sometimes the best tool is a microscopic robot.

In Nanotechnology and Precision Engineering, researchers from the Chinese Academy of Sciences and the China Electric Power Research Institute developed a microrobot capable of manipulating small droplets in the presence of magnetic fields.

To make their robot, the researchers mixed neodymium magnetic particles and sugar with a chemically stable polymer. The sugar was then dissolved away, leaving holes throughout the polymer for increased surface area. Lastly, the team treated the polymer with plasma to make it attract water and many other liquids.

"We aimed to create a cleaner, faster system that avoids residue, which is especially relevant for sensitive tasks like medical diagnostics or handling reactive chemicals," said author Lin Gui. "Ensuring chemical stability and high performance was a key priority."

Including the magnetic particles allowed the team to control their robot by applying magnetic fields. Using powerful neodymium particles made the robot more responsive and effective compared to existing magnetic microrobots.

"Previous magnetic methods struggled with weak driving forces, limiting droplet size and speed," said Gui. "Magnetic additives also often corroded or polluted samples. Designing a robot that combines strong magnetism, chemical resistance, and rapid movement requires innovative materials and engineering."

In tests, the researchers demonstrated they could use magnetic fields to guide their microrobot into a liquid droplet. They could then use their robot to drag that droplet around because of the attractive coating applied during the plasma treatment.

At slow speeds, they could bring two or more droplets together for a chemical reaction, and at high speeds, they could split a droplet into smaller pieces.

Thanks to the robot's powerful magnets, the researchers achieved speeds 20 times faster than previous microrobots, and they could transport droplets nearly a milliliter in size. Their robot could also interact with highly corrosive compounds, like acids, without any kind of damage.

The team envisions their robot being used in laboratory settings to automate certain chemical processes, or in medical settings for minimally invasive surgeries. They plan to continue to develop this technology to further increase its capabilities.

"We aim to miniaturize it for handling nanoliter droplets and explore integration with sensors for tasks like targeted drug delivery or pollution cleanup," said Gui.