An engineering team at the University of California, Berkeley has developed a groundbreaking invention—the world’s smallest wireless flying robot. Led by Professor Liwei Lin, this device measures just 9.4 millimeters in width and weighs only 21 milligrams, achieving flight capabilities comparable to those of bees; it can hover, change course, and strike small targets.

This breakthrough research addresses the fundamental challenges faced when designing micro-flying robots: how to incorporate power and control systems within an extremely compact volume. The innovation lies in eliminating both the onboard power source and control system, instead utilizing external magnetic fields for powering and controlling flight.

The robot’s 3D-printed polymer frame incorporates four horizontal propellers and a “balance ring,” with two neodymium permanent magnets held by an elevated central vertical hoop. When these magnets are subjected to attraction or repulsion from the external magnetic field, they cause the propellers to rotate, generating lift. The balance ring provides gyroscopic effects that enhance flight stability. Scientists can precisely control the robot’s movement by adjusting the external magnetic fields: increasing or decreasing magnetic strength accelerates or decelerates rotation and enables ascent or descent; altering the horizontal distribution of intensity steers left-right and forward-backward motion.

“Bees exhibit remarkable aerial capabilities, which are yet to be matched by similarly sized artificial flying robots,” explains Professor Liwei Lin. In comparison, the smallest robot with comparable flight abilities has a diameter of 2.8 centimeters—almost three times larger than this new invention.
[Image: Professor Liwei Lin (right) demonstrates the micro-flying robotic device.]

Fanping Sui, Ph.D., co-first author on the study, states: “These miniature flying robots mimic bees’ nectar-gathering mechanisms and have broad potential applications such as artificial pollination or inspection of confined spaces inaccessible to regular drones.”

Currently, this robot can only fly passively without onboard sensors for position detection or real-time flight adjustments. Professor Lin's team plans to add active control systems and further miniaturize the device—aiming for a diameter less than 1 millimeter so it can be controlled by weaker magnetic fields (such as radio waves). They are also developing ant-inspired “swarm” robots capable of performing tasks beyond individual robot capabilities, potentially even enabling minimally invasive surgery.

This research was published in *Science Advances* on March 28.
(Images courtesy: University of California Berkeley)