Given their habit of bouncing off their surroundings with surprising regularity, bumblebees certainly live up to their name. But despite their collision records, the small insects’ wings can withstand a comparatively hefty amount of damage and still function well enough to continue along their pollination routes. This surprising, natural wing strength often outperforms most flying robots’ arrays, which can be grounded by the smallest issues. It’s a resilience that recently inspired researchers to delve into just what makes bumblebees so hearty, and how engineers can mimic that in repairing their own artificial wings.
In an upcoming issue of the research journal, Science Robotics, a team at MIT detailed the new ways they improved tiny aerial robots’ actuators, aka artificial muscles, to handle a sizable amount of damage and continue flying. In this instance, the test robots were roughly the size of a microcassette tape while weighing slightly more than an average paper clip. Each robot has two wings powered by ultrathin layers of dielectric elastomer actuators (DEAs) placed between two electrodes and rolled into a tube shape. As electricity is applied, the electrodes constrict the elastomers which then cause the wings to flap.
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DEAs have been around for years, but miniscule imperfections in them can cause sparks that damage the device. Around 15 years ago, however, researchers realized that DEA failures from a single minor injury could be avoided via what’s known as “self-clearing,” in which a high enough voltage applied to the DEA disconnects an electrode from the problem area while keeping the rest of its structure intact.
For large wounds, such as a tear in the wing that lets too much air pass through it, researchers developed a laser cauterization method to inflict minor damage around the injury perimeter. After accomplishing this, they were then able to utilize self-clearing to burn away the damaged electrode and isolate the issue. To assess efficacy, engineers even integrated electroluminescent particles into each actuator. If light shines from the area, they know that portion of the actuator works, while darkened portions mean they are out-of-commission.
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The team’s repair innovations showed great promise during stress tests. Self-clearing allowed the aerial robots to maintain performance, position, and altitude, while laser surgery on DEAs recovered roughly 87 percent of its normal abilities. “We’re very excited about this. But the insects are still superior to us, in the sense that they can lose up to 40 percent of their wing and still fly,” Kevin Chen, assistant professor of electrical engineering and computer science (EECS), as well as the paper’s senior author, said in a statement. “We still have some catch-up work to do.”
But even without catch-up, the new repair techniques could come in handy when using flying robots for search-and-rescue missions in difficult environments like dense forests or collapsed buildings.
