It sounds like the plot of a sci-fi film: Thousands of tiny robotic bees swarm a blazing fire on a search-and-rescue mission. But it may not be so far-fetched. Pratheev Sreetharan has developed the Monolithic Bee, a miniature robotic bee made from a variety of advanced structural materials and fabricated through a series of steps inspired by pop-up books.
“The robotic bee project provides an experimental platform to investigate flapping wing flight at the 100 milligram scale, advancing our understanding of nature while laying the groundwork for future flapping wing devices and machines,” says Sreetharan, founder of Vibrant Research in Cambridge, Mass.
But why bees? Well…pardon the pun, but they are a hive of activity. Bee colonies are renowned for their efficiency and coordination. Thousands of bees work independently to achieve a common goal using various sensors, distinct communication protocols and a defined hierarchy of task delegation. That inspired Sreetharan and his colleagues. “A swarm of small, disposable, cheap robotic bees can take the place of a single expensive robot,” says Sreetharan. “Strength in numbers can aid in tasks such as search-and-rescue missions and military surveillance.”
The machine bees, whose bodies are about the size of a penny, consist of a rigid airframe, a piezoelectric bending actuator, a power transmission and wings. The airframe is constructed primarily from carbon fiber composites to make it lightweight and extremely rigid. The high-performance wings are made manually: Carefully laid individual carbon fibers form wing veins when bonded to a polyester film wing membrane. Other materials incorporated in the structure include brass, solder, polyimide film and piezoelectric ceramics.
The robotic bee project has its roots in Dr. Robert Wood’s graduate work at the University of California, Berkeley on the Micromechanical Flying Insect. Wood achieved the first takeoff of a robotic bee as a Harvard University electrical engineering professor in 2008. Sreetharan was a graduate student working alongside Wood in the laboratory. He was assigned the laborious task of gluing miniature robots together under a microscope.
“I was determined to find a better way to fabricate the bees,” says Sreetharan. “In 2010, I co-invented the printed circuit MEMS [Micro-Electro-Mechanical Systems] manufacturing process that has created some of the most complex composite machines and mechanisms ever. The Monolithic Bee – or Mobee – was the first machine to demonstrate this process and is the first mass-producible robotic insect at the 100 mg mass scale,” says Sreetharan. The project is funded by a grant from the National Science Foundation.