MIT Breakthrough Gives Insect-Sized Drones a Carrying Capacity Nearly Three Times Their Own Weight

A team of researchers at the Massachusetts Institute of Technology (MIT) have developed a new way to make soft actuators, which dramatically improves their efficiency — requiring 75 percent lower voltages while boosting payload capacity by 80 percent.

Earlier this year MIT researchers unveiled tiny insect-sized drones designed for high dexterity and an ability to easily navigate even the tightest of spaces. The resulting designs were entirely functional, but with one problem: The soft actuators, which flapped the drones' wings up to 500 times in a single second, were considerably more power-hungry than their rigid equivalents — meaning the tiny robots couldn't even lift their own power electronics, much less a payload.

Now, a novel fabrication technique designed to reduce the number of defects in the artificial muscles at the heart of the actuators has overcome the problem — reducing the voltage required by three-quarters and nearly doubling their carrying capacity.

"This opens up a lot of opportunity in the future for us to transition to putting power electronics on the microrobot," explains Kevin Chen, assistant professor and senior author of the group's latest paper. "People tend to think that soft robots are not as capable as rigid robots. We demonstrate that this robot, weighing less than a gram, flies for the longest time with the smallest error during a hovering flight. The take-home message is that soft robots can exceed the performance of rigid robots."

The new manufacturing process, which includes vacuuming the elastomer while wet to remove air bubbles that cause defects, altering the concentration of carbon nanotubes, and baking each layer to speed up the curing process as the number of layers increases, has a dramatic effect: A 20-layer version of the actuator demonstrated a lift-to-weight ratio of 3.7 to 1, meaning the microbots can now carry a payload almost three times their own weight.

"Two years ago, we created the most power-dense actuator and it could barely fly," Chen recalls. "We started to wonder, can soft robots ever compete with rigid robots?

"We observed one defect after another, so we kept working and we solved one fabrication problem after another, and now the soft actuator’s performance is catching up. They are even a little bit better than the state-of-the-art rigid ones. And there are still a number of fabrication processes in material science that we don’t understand. So, I am very excited to continue to reduce actuation voltage."

The team's work has been accepted for publication in the journal Advanced Materials under closed-access terms.