Researchers at the University of Pennsylvania and the University of Michigan have built the smallest fully programmable autonomous robots that can swim, overcoming long-standing physical challenges at the microscale and opening new possibilities for sensing, diagnosis and targeted treatment.
For decades the idea of tiny machines navigating the body felt like science fiction, and the phrase “Fantastic Voyage” captured that dream. The obstacle wasn’t imagination but physics: forces at micro sizes behave very differently than in our macroscopic world. These teams took a different approach by embracing those odd physical rules instead of fighting them.
The devices measure roughly 200 by 300 by 50 micrometers, putting them close to single-celled organisms and smaller than a grain of salt. They have no moving limbs or propellers; instead, each unit uses electrokinetics to move. By generating a tiny electrical field they pull charged ions in the surrounding fluid, and those ions drag water with them to create flow and propulsion.
Power comes from miniature solar cells that produce about 75 nanowatts, an amount vastly lower than consumer electronics. That constraint forced a complete redesign: ultra-low voltage circuits and a compact instruction set cram useful behavior into a few hundred bits. Despite those austerity measures, the robots can sense conditions, store brief memories and choose their next moves autonomously.
Communication and telemetry are handled without radios or antennas. Each robot performs small wiggle patterns that encode information like temperature, a scheme observers can decode through microscopy. Researchers program the swarm by flashing light patterns the robots read as commands, and a built-in passcode prevents stray illumination from corrupting their memory.
In experiments the microrobots exhibit thermotaxis, swimming toward warmer zones, which points toward real-world uses such as locating inflammation or disease markers and delivering therapeutics with pinpoint accuracy. Near-surface tasks can be powered by light; for deeper tissues researchers are investigating ultrasound as an energy source. These behaviors hint at medical and diagnostic uses that were previously impractical.
Because the devices are fabricated with standard semiconductor techniques, production scales naturally. Over a hundred robots can be made on a single chip and manufacturing yields already surpass fifty percent, which suggests that costs could fall dramatically with volume. When the per-unit cost dips toward a fraction of a cent, disposable swarms become feasible for large-scale applications.
Durability is another advantage: motion without moving parts reduces failure points and makes tiny robots easier to handle with delicate tools. Potential applications extend beyond medicine to precise material assembly and exploration of fragile environments where larger machines would be destructive. The research, published in Science Robotics, marks a step change by showing that sensing, decision-making and reliable locomotion can coexist inside something almost invisible.
