Japan develops microrobots: DNA controls movement like cells

Living things are the most inspiring, but also difficult to replicate in robotics. To achieve this goal, Japanese researchers have successfully designed a tiny robotic system that can move like a living cell. Last week, the scientists published their findings in the journal Science Robotics.

The system, called a molecular robot, is similar in size and shape to an amoeba and looks like a fluid-filled sac that contains about 27 biological and chemical components, said Ichiro Nomura, a bioengineer at Tohoku University in Sendai, Japan, who worked on the robot.

The molecular components work together to change the shape of the vesicle through stretching movements, which propels the vesicle to move like a cell in a liquid environment. The movement of the vesicle is started and stopped by using light-sensitive DNA signals.

Aside from moving in this peculiar way, the amoeba robot can't do much. But that's the beauty of the invention, Nomura said. The robot can serve as a vehicle for whatever researchers can think of: microcomputers, sensors, even drugs. Equipped with these tools, the amoeba robot system can be used to explore biomolecular environments. It can search for toxins, examine the surfaces of other cells or analyze substances in a petri dish.

Nomura and his colleagues have figured out a way to package and ship the tools so that other scientists can “happily take control of the robot” and assemble the components they need. He hopes the platform will be used to build increasingly complex molecular robots with controllable motion.

Ultimately, Nomura wants to see robots that can operate inside cells. "This is a cutting-edge technology," Nomura said. The amoeba robot can sneak into the inside of a cell and its nucleus, and can diagnose and look for problems inside the cell. "It's a bit dreamy," Nomura said, but it's worth noting that his robot can be reduced in size to less than a micron - small enough to fit inside a cell.

Researchers have developed a number of proof-of-concept micro- and nanoscale robots that can move and communicate within the body. Many of these tiny robots are made of biodegradable materials and are powered by magnetic, chemical or ultrasonic forces.

What makes Nomura's molecular robot different is that it is made entirely of biological and chemical components, moves like a cell and is controlled by DNA. None of the other molecular robots that have been developed have this kind of manipulable dynamics, Nomura said.

Nomura said it took about a year and a half to create the molecular robot using 27 different chemical ingredients. A lipid-structured membrane serves as the stretchable robot body. Inside the robot, special proteins bump into the membrane, causing it to change shape, similar to someone hitting a bag from the inside out.

Such a pounding movement only occurs when key proteins called kinesins and microtubules are connected to the membrane via an anchor unit. This connection is provided by light-sensitive DNA. When ultraviolet light shines on the robot, the light-sensitive DNA inside breaks into single strands. It can then lock onto the anchor unit and the kinesin-microtubule structure, forming a bridge between them.

Tubulins, which are rigid, long structures, slide along kinesin proteins with the help of adenosine triphosphate, or ATP, an energy transport molecule within cells. As they slide, they can hit the robot's outer membrane, causing it to change shape.

By using this combination of molecules, Nomura and his colleagues have managed to mimic the movement of cells. But if this technology is assembled entirely from biological components and chemically powered by ATP, can we really call it a robot? "The definition of a robot is very broad," Nomura said. If something has a physical body, can sense and process information and perform a function, it is a robot, he said.

Whether it’s a robot or a cellular robot, we’re looking forward to seeing what functions engineers will put inside it.

As a winner of Toutiao's Qingyun Plan and Baijiahao's Bai+ Plan, the 2019 Baidu Digital Author of the Year, the Baijiahao's Most Popular Author in the Technology Field, the 2019 Sogou Technology and Culture Author, and the 2021 Baijiahao Quarterly Influential Creator, he has won many awards, including the 2013 Sohu Best Industry Media Person, the 2015 China New Media Entrepreneurship Competition Beijing Third Place, the 2015 Guangmang Experience Award, the 2015 China New Media Entrepreneurship Competition Finals Third Place, and the 2018 Baidu Dynamic Annual Powerful Celebrity.