They’re barely larger than a human hair yet still plan to take on a cancerous tumor. We’re talking about tiny machines, 20 to 50 micrometers in size, that independently could attack malignant cells, administer medications or repair tissue in the human body. Such scenarios are still dreams of the future, but Yunus Alapan and Mehmet Berk Yigit at the Max Planck Institute for Intelligent Systems in Stuttgart have succeeded in making a major advance in research on this type of microrobot. Using a new approach, the two scientists managed to get different types of microrobots to configure themselves. The robot’s individual components independently find each other and assemble themselves into a fully functional machine.
Alapan and Yigit’s approach is based on what is known as dielectrophoresis, a process that uses non-uniform electric fields from direct and alternating currents to manipulate particles. In other words, the framework and the individual parts are exposed to an electrical field that polarizes the components. Forces similar to magnets form around them and, if you can control the forces, you can also control the individual parts and assemble them. This is exactly what Alapan and Yigit managed to do. “Depending on the shape we give the individual parts, they either attract or repel one another,” Alapan explains. He and his colleagues also code the tiny units with all the necessary information about assembly and the final shape. The design of the components generates the precise electrical field in which the parts come together into just the right shape.
The researchers’ first design is a self-assembling microcar with a magnetic drive, about 50 micrometers in size. It consists of a non-magnetic frame and magnetic wheels. In an electrical field, the chassis develops the ideal force of attraction to pull the wheels into the right position. “The approach is that the individual components of our microrobot aren’t actually mounted in place,” Yigit explains. “This way they don’t just move in one fixed direction; it means that complex movements are also possible.” The two of them steer the wheel using a rotating magnetic field and drive the microcar. The robots’ ability to perform complex movements and a variety of types of locomotion are a decisive advantage for their use in medicine. The variability means that the robots may soon be used for delivering medication or detecting and fighting tumors. The goal is to prevail against diseases much more quickly and efficiently. The idea to configure micromachines using chemical reactions and magnetic particles isn’t a new one. “We have taken magnetic self-configuration a step further,” Yigit says. Alapan and Yigit’s methodology now also makes it possible to assemble and control several robots simultaneously.
“Our goal is for our microrobots to become an integral part of medical treatment in the future,” Alapan says. “For them to fight tumors or make targeted deliveries of medication inside the body. Right now we’re researching which material is best suited for this purpose.” The human body perceives synthetic materials as foreign bodies and attacks them, making the robots ineffective. And there are other factors to consider: How can the micromachines work with absolutely no mistakes? How can a microrobot fight a tumor that is over 100 times its size? How can such a small microrobot be tracked visually in the human body? Alapan and Yigit are confident: “There’s a lot of research going on. We imagine a future in which hundreds to thousands of microrobots work together like a swarm of bees and open up new possibilities for medicine.”