Robotics | Article

Beyond Metals: Advancing Materials in Robotics

How soft materials are expected to change the shape of robotics.

Written by: Poornima Apte

Roboticists and design engineers are looking beyond metals to build robots for reasons that touch on everything from human health to manufacturing. Pliable robots can be integrated much more effectively into the human body to solve medical problems, and a soft touch on robot grippers can make a world of difference when handling fragile goods on the production and packing belt.

Most methods of creating soft robots fall into two silos, according to Carl Vause, CEO of Soft Robotics, Inc.: making rigid components soft by wrapping them in foam or soft materials, or building entire robotic systems completely out of soft materials.

Expect to see a whole suite of manufacturing techniques and applications for these soft materials. Scientists at the Massachusetts Institute of Technology have shown that synthetic polyvinyl alcohol (PVA) hydrogels can be trained to develop muscle-like properties and can be 3D printed into desired shapes. Whether these soft robotic parts are produced following the principles of thin-film electronics to create stretchable circuit wiring or through other means, robotics beyond metals is fast becoming a significant part of the field.

Soft robotic applications

Hand exoskeletons with air-powered actuators that helped patients with gripping motions were among the early applications of soft robotics in medicine. According to Carmel Majidi, Clarence H. Adamson associate professor, mechanical engineering and director of the Soft Machines Lab at Carnegie Mellon University, advances in materials science have since pushed the envelope with respect to how robotics can be integrated into the body and used in medicine.

Soft materials alone do not dictate successful robot functionality; they have to be integrated with working electrical circuitry. The problem, Majidi says, is that while from a mechanical standpoint the need is for elastic and soft materials, most candidates that qualify—such as elastomers—are not able to conduct electricity or manage heat. His lab has developed thermally conductive rubber (Thubber) and stretchable electronics that can be the base for soft robots and tattoo-like wearable circuits that might find use in healthcare, to power any type of device that can be mounted on the skin.

In the field of pick-and-place robotics, as seen in assembly lines, soft materials need powerful actuators to actually perform tasks. “It’s all about actuation, speed, precision and repeatability,” Vause says.

There are plenty of examples of biological organisms that combine sensing and data processing and motion in ways that we can’t necessarily achieve with conventional engineered hardware.
Carmel Majidi Carnegie Mellon University

From concept to design and marketplace

Because soft robot grippers better conform to objects, they don’t need as many sensors or force feedback as they would with more traditional counterparts. Companies such as Soft Robotics, Inc. have done a fantastic job of creating soft robot grippers for automated parts handling. However, commercial applications of soft robotics in medicine is still in the nascent stages, Majidi says.

“There are two sources of hiccups,” Majidi says. “First, customers are very sensitive to the cost of materials and yield and reliability. Just because you get something to work in the lab doesn’t mean it’s going to work every single time and under every single condition. Researchers must come up with manufacturing methods and material architecture that enables this high throughput, low-cost manufacturing of robust devices for real-world environments.”

Second, whatever is interesting in the lab might not be what is actually needed on a daily basis. “There is sometimes a mismatch between what is exciting to a researcher and what will make money,” he says.

According to Majidi, the solution is to not abandon the research altogether but to figure out how to marry other technologies with soft materials to make better products. It also helps for design engineers to look at nature.

“There are plenty of examples of biological organisms that combine sensing and data processing and motion in ways that we can’t necessarily achieve with conventional engineered hardware,” he says. One example currently being researched: artificial skin that not only matches the sensing properties of skin, but also its mechanical compliance and elasticity.

The many use cases for soft materials makes a compelling case for adoption of soft robotics in the marketplace. “The fact that you can achieve a really rich range of functionalities with materials that are soft and lightweight will continue to excite researchers and industry stakeholders,” Majidi says.