The device doesn’t look like much: a caterpillar-sized assembly of metal rings and strips resembling something you might find buried in a home-workshop drawer. But the technology behind it, and the long-range possibilities it represents, are quite remarkable.
The little device is called a milli-motein — a name melding its millimetre-sized components and a motorised design inspired by proteins, which naturally fold themselves into incredibly complex shapes. This minuscule robot may be a harbinger of future devices that could fold themselves up into almost any shape imaginable.
The device was conceived by Neil Gershenfeld, head of MIT’s Centre for Bits and Atoms, visiting scientist Ara Knaian and graduate student Kenneth Cheung, and is described in a paper presented recently at the 2012 Intelligent Robots and Systems conference. Its key feature, Gershenfeld says: “It’s effectively a one-dimensional robot that can be made in a continuous strip, without conventionally moving parts, and then folded into arbitrary shapes.”
To build the world’s smallest chain robot, the team had to invent an entirely new kind of motor: not only small and strong, but also able to hold its position firmly even with power switched off. The researchers met these needs with a new system called an electropermanent motor.
The motor is similar in principle to the giant electromagnets used in scrapyards to lift cars, in which a powerful permanent magnet (one that, like an ordinary bar magnet, requires no power) is paired with a weaker magnet (one whose magnetic field direction can be flipped by an electric current in a coil). The two magnets are designed so that their fields either add or cancel, depending on which way the switchable field points. Thus, the force of the powerful magnet can be turned off at will — such as to release a suspended car — without having to power an enormous electromagnet the whole time.
In this new miniature version, a series of permanent magnets paired with electromagnets are arranged in a circle; they drive a steel ring that’s situated around them. The key innovation, Knaian explains, is that “they do not take power in either the on or the off state, but only use power in the changing state”, using minimal energy overall.
The MIT researchers’ work could lead to robotic systems that can be dynamically reconfigured to do many different jobs rather than repeating a fixed function, and that can be produced much more cheaply than conventional robotics.
– David L Chandler, MIT News Office