Roboticists have built the world’s smallest autonomous robot, capable of making decisions, moving independently and surviving for months.
The microscopic bot is smaller than a grain of salt and costs just one penny to produce. The team that developed it, who hail from the University of Pennsylvania and the University of Michigan in the US, claim swarms of them could be used in a variety of roles, ranging from medicine to manufacturing.
The robot comes fully integrated with sensors and a computer, as well as tiny solar panels that allow it to operate without an external power source.
For all this to be possible, the researchers had to reimagine how it would be possible for a robot to operate at sizes below one millimetre.
"The field has essentially been stuck on this problem for 40 years,” said Marc Miskin, assistant professor in electrical and systems engineering at the University of Pennsylvania, who oversaw the robot’s development.
The difficulty lies in surface-related forces that change how movement works at microscopic scales.
Rather than gravity and inertia, tiny objects are more greatly impacted by drag and viscosity, meaning limbs and other conventional robotic designs do not work.
“If you’re small enough, pushing on water is like pushing through tar,” Assistant Professor Miskin noted. “Very tiny legs and arms are easy to break. They’re also very hard to build.”
Instead, the team developed a new way for robots to move that overcome this shift in physics.
Rather than move forward by applying Newton’s Third Law of Motion – which states every action has an equal and opposite reaction – the robots use an electrical field to cause charged particles to move forward in front of it.
When placed in a fluid, the moving particles drag nearby particles to move with them, effectively creating forward motion.
“It’s as if the robot is in a moving river, but the robot is also causing the river to move,” said Assistant Professor Miskin.
This approach allows the robots to change direction, coordinate their movement with other robots, and reach speeds of up to one body length per second – all without any moving parts.
"This is really just the first chapter," said Assistant Professor Miskin. "We've shown that you can put a brain, a sensor and a motor into something almost too small to see, and have it survive and work for months.
“Once you have that foundation, you can layer on all kinds of intelligence and functionality. It opens the door to a whole new future for robotics at the microscale."
The brain of the robot is a tiny electronic computer that features a processor, memory and sensors, making it the first sub-millimetre robot capable of real decision-making.
“We had to totally rethink the computer program instructions," said Professor David Blaauw from the University of Michigan, whose lab created the computer.
”Condensing what conventionally would require many instructions for propulsion control into a single, special instruction to shrink the program's length to fit in the robot's tiny memory space."
One of the sensors featured on the robot measures temperature, which could be used to monitor individual cells with a human body.
To report what the temperature is, Professor Blaauw said the robots perform a “little dance” that can be decoded through a microscope equipped with a camera.
“It’s very similar to how honey bees communicate with each other,” he said.
The record-breaking robot was detailed in a paper, titled ‘Microscopic robots that sense, think, act, and compute’, published in the journal Science Robotics.
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