Scientists have unveiled the world’s tiniest fully programmable, autonomous robots – microscopic swimming machines capable of sensing and responding to their environment independently.
Barely visible to the naked eye, each robot measures about 200 by 300 by 50 micrometres, smaller than a grain of salt.
The team at the University of Pennsylvania and the University of Michigan suggests that, operating at the scale of many biological microorganisms, the robots could advance medicine by monitoring the health of individual cells and by helping to construct microscale devices in manufacturing.
Powered by light, the robots carry microscopic computers and can be programmed to move in complex patterns, sense local temperatures and adjust their paths accordingly.
As described in a paper published in Science Robotics, the robots operate without tethers, magnetic fields or external joystick-like control, making them the first truly autonomous, programmable robots at this scale.
Marc Miskin, assistant professor in Electrical and Systems Engineering at Penn Engineering, is the paper’s senior author. He said: ‘We’ve made autonomous robots 10,000 times smaller – that opens up an entirely new scale for programmable robots.’
For decades, electronics have become smaller, but robots have struggled to keep pace.
Miskin added: ‘Building robots that operate independently at sizes below one millimetre is incredibly difficult. The field has essentially been stuck on this problem for 40 years.
The team designed an entirely new propulsion system that worked with, rather than against, the unique physics of locomotion in the microscopic realm.
The robots generate an electric field that nudges ions in the surrounding solution. Those ions, in turn, push nearby water molecules, animating the water around the robot’s body.
The robots can adjust the electric field that induces the effect, enabling them to move in complex patterns and even travel in coordinated groups, much like a school of fish, at speeds of up to one body length per second.
Because the electrodes that generate the field have no moving parts, the robots are highly durable.
Miskin explained: ‘You can repeatedly transfer these robots from one sample to another using a micropipette without damaging them.’
Charged by LED glow, robots can swim for months.
To be autonomous, a robot needs a decision-making computer, sensors, propulsion control, and tiny solar panels- all fitting on a chip smaller than a millimetre.
David Blaauw’s team at Michigan, holder of the world’s smallest computer record, collaborated with Penn Engineering after meeting at a DARPA event five years ago.
They realised that their technologies were complementary, but it took five years to develop their first functional robot.
The main electronic challenge was the tiny solar panels, which generated only 75 nanowatts – some 100,000 times less than a smartwatch. The team designed circuits that operated at low voltages to reduce power consumption by more than 1000-fold.
Because the solar panels occupy most of the space, they had to optimise the processor and memory, simplifying instructions to fit within the limited space.
These innovations produced the first sub-millimetre robot capable of basic cognition, with a processor, memory, and sensors – all integrated into a tiny device, making it the smallest autonomous sensing robot known.
The robots can detect temperature to within 0.3 °C, enabling them to move toward warmer areas or report temperature changes indicative of cellular activity.
They communicate temperature data through a dance pattern decoded via a microscope, similar to honeybee signalling.
The robots are powered and programmed by light pulses, each with a unique address for different tasks. This enables diverse functions within collective operations.
Miskin said: ‘This is just the beginning. We’ve shown that a tiny device with a brain, sensors, and a motor can function and survive for months. This foundation enables more advanced intelligence and opens new microscale robotics possibilities.’
