- Researchers created fully autonomous robots smaller than a grain of salt
- Robots swim using electrical fields to manipulate ions in the surrounding fluid
- The propulsion system allows coordinated movement and speeds 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 roughly 200 by 300 by 50 micrometers, smaller than a grain of salt, and operates at the scale of biological microorganisms.
The robots function 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 creating propulsion systems suitable for such small robots – as at this scale, forces like drag and viscosity dominate, making conventional limbs or body flexing ineffective.
Instead, the robots use electrical fields to manipulate ions in the surrounding fluid. These ions, in turn, push on water molecules, creating movement.
This approach allows the robots to swim in complex patterns and even coordinate in groups, reaching speeds of up to one body length per second.
Because the electrodes generating the field have no moving parts, the robots are extremely durable and can be repeatedly transferred between samples without damage.
Fitting a computer, memory, sensors, and tiny solar panels into a sub-millimeter chip presented another challenge.
Solar panels occupy most of the robot’s surface, producing just 75 nanowatts of power, over 100,000 times less than a smartwatch.
To operate under such severe energy constraints, the Michigan team condensed program instructions into extremely efficient circuits, lowering power consumption by more than a thousand times.
This allows each robot to store a program, sense its environment, and adjust its movement autonomously for months at a time.
The robots carry electronic sensors capable of measuring temperature to within a third of a degree Celsius.
They can move toward warmer areas or report measurements, with data encoded in “wiggles” of a small dance.
Researchers observe these movements under a microscope and decode the signals, analogous to how honeybees communicate.
Each robot can be programmed with light pulses, allowing unique instructions for individual robots and enabling coordinated, multi-robot tasks.
This sub-millimeter robot platform is a foundation for future advancements – its propulsion, electronics, and energy systems can be scaled to include more complex programs, additional sensors, faster movement, and operation in more challenging environments.
This achievement shows it is now possible to integrate computation, sensing, and actuation at microscopic scales.
It could also have implications for medicine, allowing individual cells to be monitored, and for manufacturing microscale devices.
Via Techxplore
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