A team of M.I.T. researchers reports in this week’s Science magazine a new way to land the tiniest drones, and keep them landed: electroadhesion. It’s the same principle that makes your hair stick to a balloon when you rub it.
So how does this help drones?
One of the biggest advantages of UAVs are their extended dwell time when observing a target. Eventually they do run out of juice, however, and need to go home, effectively closing the “unblinking eye” until a replacement shows up. The easiest solution would be simply to land and keep observing, saving energy and allowing it to stick around longer.
But landing these small UAVs is tough. They’re so small that it isn’t worth including the kind of landing gear commonly used on bigger drones (and airplanes). As a consequence many small UAVs are awkward landers: for some the standard practice is to catch a suspended rope with a hook; for others it’s to fly into large nets; others simply crash into the ground, and are built to do so over and over again. All these techniques require some preparation of the landing zone. Landing and taking off vertically makes things easier, but a slight breeze can easily send a small drone tumbling.
As is often the case, nature long ago found a solution to this problem: perching. We tend to think of perching the way birds do it—mechanically, using a special gripping toe with muscles to move it and keep it firmly in place. But there are other options: Geckos have feet with millions of tiny hairs, so many that they can use van der Waals forces to stick to virtually anything. Chemical adhesives (like glue) are even stickier, but both methods have a problem: They need additional energy to unstick, and for tiny drones, the sudden release makes flight control difficult.
Electroadhesion gets around those problems. The M.I.T team built an insect-sized drone with a flat head of copper electrodes. Running just a tiny bit of power to the electrodes allows them to stick to anything with a charge, which is just about everything. Unsticking is as simple as turning off the power. (See the video above.) Electroadhesion is used regularly in industrial settings to move delicate electronics and fabric, among other things, and though the technique has a lot of promise for designing artificial hands, cleaning dusty surfaces, and even climbing up walls, there are as yet no consumer products that rely on it.
Though the M.I.T researchers are still in the lab, they’re clearly onto something: With the ability to perch and move effortlessly, insect-size UAVs would be perfect for rescue teams searching collapsed buildings, manufacturers inspecting fragile goods, et cetera.