The field of robotics is full of surprises, with creatively designs sporting forms or functions that defy expectations of what machines can do.
In this vein, the latest buzz in miniature robotics is the “RoboBee.”
Led by engineers at Harvard University in collaboration with Northeastern University, the RoboBees project aims to create autonomous robotic insects capable of sustainable, independent flight.
The team’s primary research covered a number of areas to reach this goal, overcoming obstacles related to micro-manufacturing, actuation materials, small-scale energy storage and algorithms capable of effectively controlling individual and coordinated swarms of robots.
Micro Robots Inspired by Nature
The initial inspiration for the RoboBee came from flies and other insects. The team was intrigued by the incredible ability of small insects to self-launch, navigate and perform agile actions despite their small bodies.
"Bees and other social insects provide a fascinating model for engineered systems that can maneuver in unstructured environments, sense their surroundings, communicate and perform complex tasks as a collective full of relatively simple individuals," said Robert Wood, professor of engineering and applied sciences at Harvard, and principal investigator on the RoboBee project.
"The RoboBees project grew out of this inspiration and has developed solutions to numerous fundamental challenges -- challenges that are motivated by the small scale of the individual and large scale of the collective," Wood continued.
The current RoboBee design weighs only 84 milligrams, which is lighter than a real bee despite being about the same size.
As the project progressed, the team designed and demonstrated increasing capabilities with their miniature flying robots – from the first controlled flight of an insect scale robot back in 2012, to the current generation that can swim. The next goal: RoboBees that can sense their environment using lasers.
Conserving Energy with Biomimicry
Earlier this year, the team demonstrated RoboBees that can perch during flight to save energy, emulating bats, birds and butterflies.
“Many applications for small drones require them to stay in the air for extended periods,” said Moritz Graule, one of the researchers who participated in the RoboBees project as an engineering student at Harvard University. “Unfortunately, smaller drones run out of energy quickly. We want to keep them aloft longer without requiring too much additional energy.”
The RoboBee can stick to almost any surface, from glass to wood to a leaf. (Image courtesy of Harvard Microrobotics Lab/Harvard University.)
“A lot of different animals use perching to conserve energy,” said Kevin Ma, a post-doc at SEAS and the Wyss Institute. “But the methods they use to perch, like sticky adhesives or latching with talons, are inappropriate for a paperclip-size microrobot, as they either require intricate systems with moving parts or high forces for detachment.”
Instead, the team turned to electrostatic adhesion. This is basically the science behind the effect of a static-charged sock that clings to a pants leg or a balloon sticking to the wall.
For example, by rubbing a balloon on a wool sweater, the balloon becomes negatively charged. If the charged balloon is brought close to a wall, that negative charge forces some of the wall’s electrons away, leaving the wall’s surface positively charged. The attraction between opposite charges is what causes the balloon to stick to the wall.
“In the case of the balloon, however, the charges dissipate over time, and the balloon will eventually fall down,” said Graule. “In our system, a small amount of energy is constantly supplied to maintain the attraction.”
The RoboBee uses an electrode patch and a foam mount that absorbs shock. The entire mechanism weighs 13.4 mg, bringing the total weight of the robot to about 100mg, which is closer to the weight of a real bee. When the electrode patch is supplied with a charge, it can stick to almost any surface, from glass to wood to a leaf. To detach, the power supply is simply switched off.
“One of the biggest advantages of this system is that it doesn’t cause destabilizing forces during disengagement, which is crucial for a robot as small and delicate as ours,” said Graule.
The patch requires about 1000 times less power to perch than it does to hover, which dramatically extends the operational life of the robot. Reducing the robot’s power requirements is critical for the researchers as they work to integrate onboard batteries into untethered RoboBees.
"The use of adhesives that are controllable without complex physical mechanisms, are low power and can adhere to a large array of surfaces is perfect for robots that are agile yet have limited payload -- like the RoboBee," Wood added. "When making robots the size of insects, simplicity and low power are always key constraints."
Future Flight of the RoboBee
So what can these RoboBees be used for, either individually or as a swarm?
The research team sees them applied to assist in reconnaissance, aid in remote communications or even act as artificial pollinators in agriculture.
(Image courtesy of Kevin Ma and Pakpong Chirarattananon.)
"Aerial microrobots have enormous potential for large-scale sensor deployment to inaccessible, expansive and dangerous locations. However, flight is energy-intensive, and the limitations of current energy storage technologies severely curtail in-air operations," said Jordan Berg, an NSF program director familiar with the project.
Berg continued, "Because the capabilities of flying insects far exceed those of similarly sized machines, many researchers seek design inspiration from nature. NSF-funded projects such as this one show that innovative solutions can arise from exploiting a synergy between biological ends and engineered means."
And it’s not just the RoboBees that are enjoying the fruits of the project’s labor; members of the project have taken some of their advances into other projects.
"We have had some nice successes with translation of some of the technologies that emerged from the RoboBees project," Wood said. "For example, several of the RoboBees principal investigators are now participating in a DARPA-sponsored project making new surgical tools based on the popup microfabrication technologies developed in the RoboBees project."
Meanwhile, research on the RoboBees continues. Currently, the team is working to make the perching mechanism omnidirectional, which would enable the robot to land anywhere. They are also developing onboard power sources that could allow the RoboBees to fly completely untethered.
As exciting as these mini-robots sound, they aren’t expected to be ready for use in the real world for another five to ten years, according to Wood.
Nevertheless, this is a great example of how long-term sustained research through universities provides opportunities for engineering students.
To learn more, check out the Harvard Microrobotics Laboratory website.