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3D Printed Robotic Bat Wing Built to Study Flight

By Wesley Fenlon

A mechanical bat wing gives researchers new insight into how the wing functions mid-flight.

Taken a certain way, "Brown researchers build robotic bat wing" is a horrifying headline. Does...does that mean science has created a cyborg bat? Half machine, half screeching terror of the night? That's the most intimidating image this side of Batman. Thankfully, that's not quite what the headline means. Brown University researchers have indeed developed a robot bat wing, but not to surgically attach to a one-winged bat. Their aim is to better understand the (organic) machinations of the real thing.

The wing, modeled after a fruit bat, flaps in a wind tunnel while attached to a force transducer. That transducer then measures the aerodynamic force produced by the wing. The study also measures how much power the mechanical wing's three servo motors produce while moving the wing's seven joints. All that information adds up to create a picture of just how much energy it takes to flap a fruit bat's wing.

The researchers built a mechanical bat wing because there was no way to force bats to cooperate into flapping at a certain pace or strength. With an accurate model, they can study each dynamic of the wing separately. The Brown researchers discovered, for example, that bats fold their wings backwards during an upstroke to decrease negative lift.

How did the researchers create this accurate reproduction of a bat's wing, anyway? No surprise here: they used a 3D printer. A 3D printer created the mechanical wing's plastic "bones," while a silicone elastomer took the place of stretchy skin. Impressive as the wing's seven joints are, it's actually far simpler than a real bat's wing, which has 25 joints. But simplifying the design makes the bat's wing easier to study without sacrificing the basics of its functionality. The researchers did find, however, that some mechanical flaws could be overcome with organic-like modifications.

"During testing, for example, the tongue and groove joint used for the robot’s elbow broke repeatedly," writes the Brown University News. "The forces on the wing would spread open the groove, and eventually break it open. [Grad student] Bahlman eventually wrapped steel cable around the joint to keep it intact, similar to the way ligaments hold joints together in real animals...The wing membrane provided more lessons. It often tore at the leading edge, prompting Bahlman to reinforce that spot with elastic threads. The fix ended up looking a lot like the tendon and muscle that reinforce leading edges in bats, underscoring how important those structures are."

Cyborg bats may not be too far off, after all.