Image: Duduta et al.
Robots are increasingly able to outperform humans in a variety of mundane tasks (and even in more technical areas like surgery), but for all that efficiency they are still by and large one trick ponies. Most robots are designed to perform one very specific task and part of taking robotics to the next level is designing a multifunctional robot that can move with enough speed to make multifunctionality a desirable feature.
To overcome this design problem, engineers have begun studying Mother Nature’s own solution to multifunctionality, which has given rise to a field of bio-inspired robotics. One of the newest areas of bio-bot research involves the creation of soft robots, where the idea is to take a cue from animals like the octopus and starfish and make a robot that is only made of soft components. Soft robotics is, in essence, the art and science of designing artificial muscles.
Just in the last five years engineers have seen enormous breakthroughs in soft robotics, but a fundamental problem still remains: these robots are still moving at starfish-like speeds. This is why a new approach to engineering robot muscles pioneered by researchers at Harvard’s School of Engineering and Applied Sciences which allows for flexible, efficient circuitry is being heralded by soft roboticists as “the holy grail” of the field.
The technical term for the artificial muscles that make a soft robot move is "actuators," and historically these actuators have relied on hydraulic or pneumatic components (which make use of liquids or compressed gases, respectively) to function. The downside of pneumatic and hydraulic actuators is that they are slow to respond and rigid—which kind of defeats the whole point of soft robotics. Some engineers have looked at using soft, insulating materials called dielectric elastomers as an alternative to pneumatic actuators, but they also require rigid components and high voltage to deal with their complex and inefficient circuitry.
A soft robot engineered at Harvard in 2011.
In this sense, the latest development out of Harvard is something of a revolution for dielectric elastomers. The research, published this week in Advanced Materials, culminated in the development of a dielectric elastomer that has a broad range of motion and hyper-efficient circuitry, thus requiring relatively low voltage to function.
“Electricity is easy to store and deliver, but until now the electric fields required to power actuators in soft robots has been too high,” said Mishu Duduta, a Harvard engineering graduate student and the paper’s lead author. “This research solves a lot of the challenges in soft actuation by reducing actuation voltage and increasing energy density, while eliminating rigid components.”
To make their paper-thin device, Duduta and his colleagues made use of a new type of elastomer developed at UCLA which doesn’t need to be pre-stretched over a rigid frame like other elastomers. For the device’s electrode, they used carbon nanotubes developed at Harvard instead of the typical carbon grease.
According to the team, this breakthrough could find use in everything from minimally invasive surgical tools to the artificial muscles for more complex and traditional robots.
"Actuation is one of the most difficult challenges in robotics," said Robert Wood, a Harvard professor of engineering and co-author of the new paper. "This breakthrough in electrically-controlled soft actuators brings us much closer to muscle-like performance in an engineered system and opens the door for countless applications in soft robotics."