Have you read Isaac Asimov’s Fantastic Voyage? It is a story about shrinking a submarine and crew to microscopic size to insert them into a scientist’s bloodstream to travel to the brain to dissolve a blood clot. That was fantasy.
Now for a reality that Asimov would have enjoyed!
Researchers at the University of Pennsylvania and the University of Michigan recently described their invention of a sub-millimetre-sized robot no bigger than a grain of salt. The robot contains all the technology necessary for doing onboard computation, sensing, memory, locomotion and communication. An article, “Microscopic robots that sense, think, act, and compute,” appeared in the December 10, 2025, edition of the journal Science Robotics.
The robot’s inventors state it paves “the way for general-purpose microrobots that can be programmed many times in a simple setup and can work together to carry out tasks without supervision in uncertain environments.”
Shrinking a device to this size is one thing, but giving it the capability to act autonomously represents a significant step forward. David Gracias, a professor in the Department of Chemical and Biomolecular Engineering at Johns Hopkins University, recently told The Washington Post, “In the future, let’s say 100 years, anything a surgeon does today, we’d love to do with a robot.” He added, “We are not there yet.” David Blaauw, one of the paper’s authors, sees getting there in ten years.
Just how small is this microbot? It is equivalent to the smallest biological units, our living cells, which measure between 20 and 40 microns across. For comparison, the diameter of a human hair is 70 microns.
The microbot contains the same materials as a microchip: silicon, platinum and titanium. Its embedded sensors respond to temperature. It harvests energy from built-in solar panels. Onboard electrodes attract charged particles to generate locomotion. Inspired by the dancing waggles of honeybees, the microbot communicates to an external operator what it is doing and seeing using similar movements.
What does it take to make a robot this small? Its inventors describe how they have leveraged semiconductor manufacturing “to lithographically build the robot’s body, actuators, and information systems massively in parallel,” allowing them to shrink its size by 10,000-fold. They were able to work within a power limit of ~100 nanowatts (nW), about the same amount of energy used by transistors in radio telescopes. For comparison, 1 watt equals 1,000,000,000 nanowatts.
In the previously mentioned Washington Post article, Marc Miskin, from the Department of Electrical and Systems Engineering at the University of Pennsylvania, describes an invitation to high school students to test these microbots. Miskin describes how the students tracked the robots using a microscope. He further stated that the version the students saw cost about US$10.
The grain-of-salt-sized microbot can move through watery environments but not yet saltwater. The teams are working on making that happen, as well as ways to exploit its use in other environments.
David Blaauw, another member of the research team, in the Department of Electrical Engineering and Computer Science at the University of Michigan, told the Washington Post, “The next holy grail…is for them [the microbots] to communicate with each other.”
Ouch to that last comment because, in Michael Crichton’s science fiction novel, Prey, that’s exactly what happens when a laboratory-created nanotechnology escapes and goes awry, turning a self-replicating microbot swarm, imbued with predator instincts, into an existential threat to humans.
