- Researchers created fully autonomous robots smaller than a grain of salt.
- The robots swim using electric fields to manipulate ions in the surrounding fluid.
- The propulsion system allows coordinated movements and accelerates up to one body length per second.
Researchers at the University of Pennsylvania and the University of Michigan claim to have created the world’s smallest fully programmable autonomous robots.
Each robot measures approximately 200 by 300 by 50 micrometers, smaller than a grain of salt, and operates at the scale of biological microorganisms.
The robots operate without tethers, magnetic fields or external joysticks, making them the first truly autonomous devices of this size.
Swimming through microscopic physics
The team faced challenges in creating propulsion systems suitable for such small robots, as forces such as drag and viscosity dominate at this scale, making conventional limbs or body bending ineffective.
Instead, robots use electric fields to manipulate ions in the surrounding fluid. These ions, in turn, push the water molecules, creating movement.
This approach allows robots to swim in complex patterns and even coordinate in groups, reaching speeds of up to one body length per second.
Because the electrodes that generate the field have no moving parts, the robots are extremely durable and can be repeatedly transferred between samples without damage.
Installing a computer, memory, sensors and small solar panels on a submillimeter chip represented another challenge.
The solar panels take up most of the robot’s surface and produce only 75 nanowatts of energy, more than 100,000 times less than a smartwatch.
To operate under such severe power constraints, the Michigan team condensed the program’s instructions into extremely efficient circuits, reducing power consumption more than a thousand-fold.
This allows each robot to store a program, detect its environment and adjust its movement autonomously for months.
The robots carry electronic sensors capable of measuring temperature with an accuracy of one-third of a degree Celsius.
They can move toward warmer areas or report measurements, with data encoded in “movements” of a small dance.
Researchers observe these movements under a microscope and decode the signals, analogous to how bees communicate.
Each robot can be programmed with light pulses, allowing unique instructions for individual robots and enabling coordinated tasks of multiple robots.
This submillimeter robot platform is the foundation for future advancements: its propulsion, electronics and power systems can be scaled to include more complex programs, additional sensors, faster movements and operation in more challenging environments.
This achievement shows that it is now possible to integrate computing, sensing and actuation at microscopic scales.
It could also have implications for medicine, as it would make it possible to monitor individual cells and to make microscale devices.
Via Techxplore
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