Origami-inspired robots promise significant strength in a soft, squishy shell

I’ve made a few origami frogs in the past, and while they did successfully hop, I never appreciated how close I was to making a robot. The amount of potential and kinetic energy in the frog’s flexing legs seemed negligible, but apparently carefully controlled folding can not only trigger movement, but it can offer some considerable strength as well. While my little paper frogs weren’t about to do any heavy lifting, researchers from Harvard and MIT have found that lightweight, foldable materials can do a lot of work, even moving objects 1,000 times their own weight.

Air-powered contraction and expansion

The key to these folded robots is how they turn folded materials into veritable motors. A simple example uses a strip of stiff paper or plastic, folded in a basic accordion shape. That zig-zagging strip functions as a sort of “skeleton” for the machine, but it needs an outer covering to be activated. A simple plastic bag sealed around the folded strip is sufficient to act as the machine’s “muscles,” as long as that bag has a valve that can manipulate air flow. Sucking the air out of the valve with an air pump naturally causes the bag to contract, constricting around the folded paper. As the whole machine contracts, it’s strong enough to lift a weight many times its own mass. Letting air back into the bag allows the folded strip to expand again, lowering the weight in a controlled manner. In short, it’s a simple crane, powered by lightweight materials and a vacuum pump.

A folded strip is only the beginning though, as well-placed creases and joints in the inner skeleton can make for much more complicated articulation. One prototype was a four-pronged claw that can contract with enough strength to lift a tire. Another was a multi-jointed arm, ending in a flower-shaped gripper that can open and close as air is added or removed from the system. While they promise outsized strength, each design works with very simple, zig-zagged folds in the internal plastic structures, keeping them lightweight and very importantly, squishy.

Softer and safer

We have many machines that can lift a lot of weight, but the strength exhibited by these machines is quite noteworthy for something that’s soft and relatively safe. With no hard motors, actuators, joints or power sources, these machines can be used in places that harder robots wouldn’t be appropriate, like close to the human body. Since less than an ounce of foldable machine can lift over six pounds of weight, researchers think these gentle robots could be fit to human bodies, supporting or augmenting people who need help with certain tasks. They’d need to have a way to inflate and deflate the machine, but it would still be safer and more comfortable than carrying a huge set of gears, servos or hydraulic pistons.

At this point, researchers still haven’t made a jumping frog, unfortunately. The snap you get when releasing an origami frog is actually a bit speedy for these machines, as they can only move as fast as they’re inflated. An upcoming goal instead focuses on maximizing strength and articulation, as researchers aim to build a robotic elephant trunk. Since a trunk contains no hard bones but is incredibly mobile thanks to its 150,000 muscle fascicles, or muscle sections. It will likely require some carefully coordinated folding, but it would also prove that these inflation-based “muscles” will allow for very versatile machines in the near future.

Source: Artificial muscles give soft robots superpower, Phys.org