Northwestern builds smallest-ever remote-controlled walking robot


Nanobot takes one small step for robot-kind.

Article Image

Image by Northwestern University

By Ethan Attwood

Engineers at Northwestern University have just set a new record for the world’s smallest remote-controlled walking robot.

The design is based on the Atlantic Rock Crab, also known colloquially as a “peekytoe”. The microscopic robo-crustacean measures in at half a millimetre wide, smaller than a flea and just visible to the human eye. It’s agile too – bendable, twistable, and able to walk, crawl and jump – making it a prime candidate to model more specific designs for applications from medicine to manufacturing requiring fine work in confined spaces.

Lead researcher John A. Rogers envisions a litany of places for his creation to venture. “You might imagine micro-robots as agents to repair or assemble small structures or machines in industry or as surgical assistants to clear clogged arteries, to stop internal bleeding or to eliminate cancerous tumours — all in minimally invasive procedures.”

One of the many fascinating technologies used in the Northwestern research was in assembling the robot from shape-memory alloys. These space-age metal components exist in one shape while cool, but deform into a different one upon heating. They are already being used as cardiovascular stents; tiny metallic meshes that can be inserted into an artery while narrow and cold, which then expand into a supportive structure when heated by the body. The same principle was used to solve a persistent problem in nanorobotics – locomotion. A laser is used to rapidly control heating and cooling cycles of the robot’s alloy to stimulate movement. “Because these structures are so tiny, the rate of cooling is very fast,” Dr. Rogers explained. “In fact, reducing the sizes of these robots allows them to run faster.”

Of course, this means the robot can’t move on its own for now, and developing motors and mechanical parts on this scale remains a challenge. Targeted laser heating in confined spaces would be nigh-on impossible, and the ambient temperature of live tissue would make this approach difficult anyway. So for now, maintenance of mechanical systems remains the application for nanorobotics closer to realisation. Northwestern’s researchers are determined to take inspiration from nature, and have created millimetre-scale nanobots resembling inchworms, crickets and beetles, though the crab is their favourite. “The students felt inspired and amused by the sideways crawling motions of tiny crabs. It was a creative whim” added Rogers. While this approach never worked out so well for the Wright brothers, the natural laws governing machines and organisms are one and the same, it simply depends on scale. And the aspiration to join birds in the air was what originally set Orville and Wilbur’s imaginations alight.

Nanorobotics don’t always enjoy the most favourable perception within the public consciousness. 2016 Black Mirror episode Hated In The Nation features robots called “Autonomous Drone Insects” introduced by the government to replace extinct bees (an all-too-real impending catastrophe worthy of its own article). These miniature drones are then co-opted by nefarious agents to assassinate targets of online animosity, with surgical effectiveness. While Black Mirror’s MO tends to be vilifying pretty much every aspect of technology, nanorobotics have been the subject of numerous conspiracy theories in other circles, including their supposed implantation into coronavirus vaccines. Advanced technology that is by definition difficult to see and hear is an understandable object of human fear. Viral videos of China’s use of drones to quell civil disobedience in recently locked-down Shanghai doesn’t help the poor robots’ case.

History is on the side of technology however, once it shows utility for making tangible improvements to our lives. Nanotechnology is already used in the form of nanoparticles that reflect UV light in sunscreen and make fabrics water repellent. Carbon nanotubes make tennis rackets more durable. On the autonomous systems side, robotics have been assisting surgery for more than 30 years, and machine learning has become integrated in almost every aspect of our technological lives. It’s only a matter of time before these two research streams combine, and a half-millimetre robotic crab is taking the first steps on that journey.