In a groundbreaking development, researchers from the University of Pennsylvania and the University of Michigan have unveiled the world’s smallest fully programmable, autonomous robots. These microscopic swimming machines, capable of independently sensing and responding to their environment, promise to revolutionize fields such as medicine and manufacturing. Remarkably, each robot costs just a penny and can operate for months.
Measuring a mere 200 by 300 by 50 micrometers—smaller than a grain of salt—these robots operate at the scale of many biological microorganisms. Their potential applications are vast, from monitoring the health of individual cells to assisting in the construction of microscale devices. Powered by light, these robots carry microscopic computers and can be programmed to move in complex patterns, sense local temperatures, and adjust their paths accordingly.
Breaking the Sub-Millimeter Barrier
The creation of these robots marks a significant achievement in overcoming a longstanding challenge in robotics. For decades, while electronics have continually shrunk, robots have struggled to operate independently at sizes below one millimeter. According to Marc Miskin, Assistant Professor in Electrical and Systems Engineering at Penn Engineering, “Building robots that operate independently at sizes below one millimeter is incredibly difficult. The field has essentially been stuck on this problem for 40 years.”
At such a small scale, forces like drag and viscosity dominate, making traditional propulsion methods ineffective. “If you’re small enough, pushing on water is like pushing through tar,” Miskin explains. The team had to innovate a new propulsion system that works with the unique physics of the microscopic realm.
Making the Robots Swim
Unlike larger aquatic creatures that propel themselves by flexing their bodies, these robots generate an electrical field that nudges ions in the surrounding solution, causing nearby water molecules to animate. This method allows the robots to move in complex patterns and travel in coordinated groups, much like a school of fish, at speeds of up to one body length per second. The absence of moving parts makes the robots extremely durable, capable of being transferred between samples without damage.
Giving the Robots Brains
To achieve true autonomy, the robots needed a computer to make decisions, electronics to sense their surroundings, and tiny solar panels to power everything. David Blaauw’s team at the University of Michigan, known for holding the record for the world’s smallest computer, collaborated with Miskin’s team to integrate these components. “We saw that Penn Engineering’s propulsion system and our tiny electronic computers were just made for each other,” says Blaauw.
The challenge lay in the limited power produced by the tiny solar panels. To address this, the Michigan team developed special circuits that operate at extremely low voltages, reducing the computer’s power consumption significantly. Despite the solar panels occupying most of the robot’s space, the team managed to fit the processor and memory within the remaining area by condensing the computer program instructions.
Robots that Sense, Remember, and React
This technological breakthrough enables the robots to sense and act independently. Equipped with electronic sensors, they can detect temperature changes with high precision, allowing them to monitor cellular activity. The robots communicate their findings through a unique “dance” that encodes information, reminiscent of how honey bees communicate.
Each robot is programmed using pulses of light that also power them, with unique addresses allowing for different programs to be loaded onto each robot. “This opens up a host of possibilities,” adds Blaauw, “with each robot potentially performing a different role in a larger, joint task.”
Only the Beginning
The current design of these robots serves as a general platform, with potential for future versions to store more complex programs, move faster, and integrate new sensors. “This is really just the first chapter,” says Miskin. “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.”
The studies were conducted at the University of Pennsylvania’s School of Engineering and Applied Science and the University of Michigan’s Department of Electrical Engineering and Computer Science. The research received support from several organizations, including the National Science Foundation and the Air Force Office of Scientific Research.
As researchers continue to explore the capabilities of these microscopic robots, the potential applications in medicine, manufacturing, and beyond are vast. The development of these robots represents a significant step forward in the field of robotics, opening the door to a new era of innovation at the microscale.
