A gearbox driven by an external magnetic field can power tiny but powerful robots that crawl like a caterpillar or jump almost 40 times their own height, despite having no batteries or motors on board. The technology could lead to medical robots that can travel through the human body, taking samples or delivering drugs.
Soft robots – which have no batteries, motors or electronics and are powered and controlled remotely by light or magnets – are a popular field of research because their simplicity enables them to be highly miniaturised. But they may be lacking in power when the task requires puncturing skin or opening collapsed cavities.
Now, Chong Hong at the Max Planck Institute for Intelligent Systems in Germany and his colleagues have created a gearbox that measures around 3 millimetres across and is equipped with cogs as small as 270 micrometres in diameter.
The gears are cast from epoxy resin impregnated with aluminium. A magnet fitted to the input shaft is driven by an external, spinning magnetic field that amplifies the torque – or rotational force – by up to 342 times.
These gearboxes – which contain seven gears to amplify the input – can be fitted into various modular robots to accomplish a range of tasks: one crawls like a caterpillar at 0.68 millimetres per second, another stores energy in elastic legs and jumps 119 millimetres, while others clamp on to solid objects which they puncture with a needle.
When put to the test, a winch-like robot equipped with a gearbox was able to lift 103 grams.
Hong says the technology can allow the creation of more powerful and complex soft robots, although they will need solid gearbox machinery at their core.
“In the future we may use the robot in confined spaces, like the human body, or in granular media [such as sand] like [how] an earthworm [moves],” he says.
“Compared to other magnetic robots, ours just requires a very small magnetic field, so we can put our control system far away from the robot, because the gearbox amplifies the magnetic force to function. So maybe this robot can obtain a larger working distance [than existing soft robots].”