MIT’s Tiny Robotic Lightning Bugs Take Flight
Inspired by fireflies, scientists create insect-scale robots that can emit light when they fly, which enables motion tracking and communication.
Lightning bugs that light up dusky backyards on warm summer evenings use their luminescence for communication — to attract a mate, ward off predators, or lure prey.
These glimmering fireflies also sparked the inspiration of researchers at MIT. Taking a cue from nature, they constructed electroluminescent soft artificial muscles for flying, insect-scale robots. The tiny artificial muscles that control the robots’ wings emit colored light during flight.
This electroluminescence could enable the robots to communicate with each other. For example, if sent on a search-and-rescue mission into a collapsed building, a robot that finds survivors could use lights to signal others and call for help.
The ability to emit light also brings these microscale robots, which barely weigh more than a paper clip, one step closer to flying on their own outside the lab. These robots are so lightweight that they can’t carry sensors, so researchers must track them using bulky infrared cameras that don’t work well outdoors. Now, they’ve shown that they can track the flying robots precisely using the light they emit and just three smartphone cameras.
“If you think of large-scale robots, they can communicate using a lot of different tools — Bluetooth, wireless, all those sorts of things. But for a tiny, power-constrained robot, we are forced to think about new modes of communication. This is a major step toward flying these robots in outdoor environments where we don’t have a well-tuned, state-of-the-art motion tracking system,” says Kevin Chen, who is the D. Reid Weedon, Jr. Assistant Professor in the Department of Electrical Engineering and Computer Science (EECS), the head of the Soft and Micro Robotics Laboratory in the Research Laboratory of Electronics (RLE), and the senior author of the paper.
He and his colleagues accomplished this by embedding minuscule electroluminescent particles into the artificial muscles. This process adds just 2.5 percent more weight without impacting the flight performance of the robot.
The research was published recently in IEEE Robotics and Automation Letters. Joining Chen on the paper are EECS graduate students Suhan Kim, the lead author, and Yi-Hsuan Hsiao; Yu Fan Chen SM ’14, Ph.D. ’17; and Jie Mao, an associate professor at Ningxia University.
Previously, these scientists demonstrated a new fabrication technique to build soft actuators, or artificial muscles, that flap the wings of the robot. These durable actuators are made by alternating ultrathin layers of elastomer and carbon nanotube electrodes in a stack and then rolling them into a squishy cylinder. When a voltage is applied to that cylinder, the electrodes squeeze the elastomer, and the mechanical strain flaps the wing.
To fabricate a glowing actuator, the researchers incorporated electroluminescent zinc sulfate particles into the elastomer but had to overcome several challenges along the way.
First, the team had to create an electrode that would not block light. They built it using highly transparent carbon nanotubes, which are only a few nanometers thick and enable light to pass through.