Researchers from the University of Pennsylvania and the University of Michigan have unveiled the smallest fully programmable autonomous robots, marking a significant breakthrough in robotics. These microscopic machines, measuring approximately 200 by 300 by 50 micrometers—smaller than a grain of salt—can swim through liquids, sense their environment, and operate independently for extended periods. Each robot costs about one penny to produce, making them an affordable innovation in the field.
The findings were detailed in the journals Science Robotics and Proceedings of the National Academy of Sciences. Unlike previous designs, these robots do not rely on wires or external controls, establishing them as the first truly autonomous robots at such a diminutive scale. According to Marc Miskin, Assistant Professor in Electrical and Systems Engineering at Penn Engineering and the senior author of the papers, “We’ve made autonomous robots 10,000 times smaller. That opens up an entirely new scale for programmable robots.”
Challenges in Microscopic Robotics
Despite advancements in electronics shrinking over the years, robotics has lagged behind, particularly at sizes below one millimeter. Miskin highlights that achieving independence at these scales has posed a challenge for four decades. The dynamics of motion at microscopic sizes are governed more by surface forces than by gravity and inertia, which complicates traditional robotic designs.
“Building robots that operate independently at sizes below one millimeter is incredibly difficult,” he notes. Conventional components, such as tiny arms and legs, often break easily and are challenging to manufacture. To address these issues, the research team developed an innovative propulsion method tailored to microscopic physics.
Innovative Swimming Mechanism
Unlike larger swimmers that propel themselves by pushing water backward, these robots harness electrical fields to create motion. They gently push charged particles in the surrounding liquid, dragging water molecules along with them. “It’s as if the robot is in a moving river,” Miskin explains. This unique approach allows the robots to change direction and coordinate movements, achieving speeds of up to one body length per second.
Powered by light from an LED, these robots can swim continuously for months. Their design features no moving parts, which enhances durability, allowing them to be transferred between samples without damage.
The integration of intelligence into these microscopic bodies is equally crucial. The robots can sense their environment, make decisions, and operate autonomously. This aspect was addressed by a team led by David Blaauw at the University of Michigan, which specializes in creating compact electronic systems.
The collaboration between Blaauw and Miskin began five years ago, revealing how their respective technologies could work together. The challenge of power consumption was significant, as the tiny solar panels generate only 75 nanowatts—over 100,000 times less than a standard smartwatch. To overcome this, specialized circuits were designed to operate at low voltages, significantly reducing power consumption.
Decision-Making and Communication Capabilities
The result is a sub-millimeter robot capable of real decision-making, a feat unprecedented in the field. The robots can detect temperature changes as minor as one-third of a degree Celsius, enabling them to navigate toward warmer areas or report values indicative of cellular activity.
To communicate these measurements, the researchers devised an inventive method: the robots perform a “dance” that encodes temperature data. A microscope and camera can then decode these movements, reminiscent of how honey bees convey information to one another. Each robot possesses a unique address, allowing researchers to upload different instructions, paving the way for diverse roles in collaborative tasks.
A Foundation for Future Innovations
While the current iteration of these robots represents a significant achievement, researchers believe this is merely the beginning. Future models may integrate more complex programs, enhance their speed, include additional sensors, or operate in challenging environments. The platform developed is versatile, combining robust propulsion with cost-effective electronics that can adapt over time.
“This is really just the first chapter,” Miskin asserts. “We’ve shown that you can put a brain, a sensor, and a motor into something almost too small to see, and have it survive and work for months. Once you have that foundation, you can layer on all kinds of intelligence and functionality.”
The research was funded by the National Science Foundation, the University of Pennsylvania Office of the President, the Air Force Office of Scientific Research, the Army Research Office, the Packard Foundation, the Sloan Foundation, and the NSF National Nanotechnology Coordinated Infrastructure Program, along with contributions from Fujitsu Semiconductors.
