Flying robotic insects took first controlled flight

Researchers at Harvard University have developed insect-sized flying robots that mimic nature and, in the process, have stretched the frontier of science in the production of nanomaterials and tiny computers, albeit still smarter than the average insect's brain.

In the very early hours of one morning last summer at the Harvard University Robotics Lab, a robotic insect began to fly. It is half the size of a paper clip, and weighs less than a tenth of a gram. It jumped a few inches, hovered for a moment on fragile, flapping wings, then sped through the air on a predetermined route.

Like a proud parent watching his child's first steps, Pakpong Chirarattananon immediately took a video of the chick taking off and sent it to his PhD supervisor and colleagues at three in the morning. In the subject line he wrote: "Flight of RoboBee".

"I was so excited, I couldn't sleep," recalled Chiratananon, co-lead author of the article published this week in the journal Science.

The success of the first controlled flight of an insect-sized robot is the culmination of more than a decade of work led by researchers at Harvard University's School of Engineering and Applied Science and Harvard University's Wyss Institute for Bio-Inspired Engineering.

"That's what I've been trying to do for literally the last 12 years," says Robert Wood, professor of engineering and applied science, Wyss faculty member, and principal investigator of the National Science Foundation, which supports the RoboBee project. "It's really only thanks to this laboratory's recent breakthroughs in production, materials, and design that allowed us to even try this. And it just worked, most spectacularly. "

Inspired by the biology of a fly, with sub-millimeter scale anatomy, the robot flaps two thin, almost invisible wings at a rate of 120 times per second. "The tiny device represents the absolute cutting edge of micromanufacturing and control systems and has helped drive innovation in these areas by dozens of researchers across Harvard for years."

"We were required to develop solutions from the beginning, for everything," explains Wood. "Every time we solved one problem, five new problems emerged. It was a moving target," he said.

Flight muscles, for example, don't come prepackaged for finger-sized robots. "Large robots can run on electromagnetic motors, but at this small scale, alternative solutions are needed, and there were none," says one of the authors Kevin Ma, a graduate student.

The tiny robot flaps its wings by activating strips of ceramic that expand and contract when an electric field is applied. Thin plastic hinges were inserted into a carbon fiber body frame and served as joints, and a delicately balanced control system controlled the rotation of the robot's movements expressed in the flapping of the wing. Each wing was controlled independently in real time.
On the tiny scale, small changes in airflow can have a larger-than-usual effect on flight dynamics, and the control system must react much faster to keep the robot stable [the system]).

For the production of the robotic insects, the developers utilize the ingenious production technique developed by Wood's team in 2011. Sheets of different materials are laser cut layer by layer and pushed together into a thin surface that folds like a children's book from which cardboard figures jump out, but instead of the cardboard figures it is a complete electronic circuit.

The quick, step-by-step process replaces what was supposed to be a manual for precision art and allows Wood's team to use stronger materials and new combinations, improving the overall accuracy of each device.

"Now we can quickly build a reliable prototype, which allows us to be more aggressive in the way we test them," Ma says, adding that the team has tested 20 prototypes in the past six months.

Applications of the RoboBee project could include environmental monitoring, search and rescue operations, military and intelligence applications or to help with crop pollination. However, it is possible that the materials, production techniques and components developed within it over the years may turn out to be even more significant. For example, in the process of producing the 'pop-up book' it is possible to produce a new type of complex medical devices.

Harvard's Office of Technology Development and the Wyss Institute are already in the midst of commercializing some of these technologies.

"Biology harnessed to solve real-world problems is what the Wyss Institute is all about," says the institute's founder and director, Don Ingeber. "This work is a beautiful example of how bringing together scientists and engineers from many fields to carry out research inspired by nature - can lead to important technical breakthroughs."

And the project continues. "Now that we have this unique platform, there are dozens of tests we are starting to do, including controlling more aggressive maneuvers and landing the insect," says Wood.

The next steps will involve combining the parallel work of many different research teams working on the brain, colony coordination behavior, power source, and so on, until the robotic insects are fully autonomous and wireless.

The prototypes are still tethered by a very thin electrical cable, because there are no off-the-shelf energy storage solutions that would be small enough to be mounted on the robot's body. Before the RoboBees can fly independently, fuel cells for high-density energy storage must be developed.

The control is also done from a separate computer and not from the robot's 'brain'. This is despite the fact that a separate team is working on developing an efficient brain that can handle the computing power required for the robot.

"The aerobatic performance of flies is the most amazing in nature and is done with the help of a tiny brain," notes co-author Sawyer Fuller, a postdoctoral researcher on Wood's team who studied how fruit flies cope with windy days. "Their capabilities exceed what we can do with our robot, so we want to understand their biology better and apply it to our work."

"This project provides shared motivation for scientists and engineers across the university to build smaller batteries, design more efficient control systems, and create stronger and lighter materials," says Wood. "You might not expect all these people to be working together with vision specialists, biologists, material scientists, electrical engineers and more. What do they have in common? Well, everyone enjoys solving really hard problems."

"I want to create something the world has not seen before," adds Ma. "It's exciting to stretch the limits of what we think we can do, and the limits of human ingenuity."

This research was supported by the National Science Foundation and the Wyss Institute for Biologically Inspired Engineering at Harvard University.