Dora Guo, Illustrations Editor

Researchers at Yale have developed active fibers that can be sewn onto fabric, allowing it to bend into complex shapes and reset autonomously.

Rebecca Kramer-Bottiglio, professor of mechanical engineering and materials science, is the principal investigator of the project. She leads a team of researchers in her ‘Faboratory,’ housed within Mason Laboratory. The Faboratory uses creative materials to bridge the gap between the soft, adaptable mechanisms of the natural world and the rigid structures typically found in modern robotics. 

In a paper published in the Proceedings of the National Academy of Sciences last month, Kramer-Bottiglio and three researchers in her lab discussed their study of robotic fabric along with several applications of the technology.

“Fabrics have conventionally been passive materials with static properties,” Kramer-Bottiglio wrote in an email to the News. “In this paper, we present a set of functional fibers that we developed to ‘roboticize’ everyday fabrics as a platform for reconfigurable robots.”

In order to make this possible, Kramer-Bottiglio and her team attached thin, heat-activated fibers to simple fabric using standard sewing techniques. The properties of the fibers and the method of attachment transform the fabric into a soft robot that can move and stiffen into a series of programmable shapes.

Courtesy of Yale School of Engineering and Applied Science

Temperature plays a key role in the adaptability of the fabric-based robots, according to the paper. Heating the functional fibers makes them soft and therefore highly flexible. Once bent into the programmed position, cooling will cause them to become rigid, at which point the robotic fabric can maintain its shape and even hold small amounts of weight. Heating again will return the system to its original state, all without human intervention, the paper explains.

Adam Bilodeau, who earned his PhD this past May after six years with the Faboratory, expressed that one of the most difficult aspects of this project was getting the robotic fabric creations to smoothly self-deploy and recompress. The initial fibers were prone to twisting the fabric rather than bending it, and Bilodeau compared early attempts to a tangled Slinky. “Certainly not autonomous,” he said. Trevor Buckner, 5th-year PhD student in Kramer-Bottiglio’s lab and first author of the study, was able to work out these kinks by altering the shape of the fibers.

“Once we had clean motion, everything else was so much easier to connect on top of that,” Buckner said.

The paper suggests that a tent-like configuration of their robotic fabric could inspire preliminary versions of self-deploying shelters. In contrast to previous shape-changing robots that rely on distinct, predetermined folds in the material to form a limited amount of structures, the Faboratory has leveraged the softness of fabric to create a highly versatile product.

Along with the fibers that determine shape and rigidity, the team also painted strips of specialized ink on the fabric which can sense damage or environmental changes. While this sensing capability has implications for a variety of applications, the paper specifically discusses it in the context of a robotic fabric tourniquet.

“This type of responsive sleeve could potentially be used as a smart garment in military or exploratory environments, where automatic emergency measures could counteract life-threatening situations if medical aid is not immediately available,” the paper reads.

When a portion of the sensing ink is damaged, the robot reacts, initiating the programmed response for the fibers to contract around the fabric and tighten the tourniquet. The team was careful to make sure that the sensing ink would not inhibit the components of the fabric — primarily breathability and flexibility — that make it such an ideal material for wearable applications.

John Rogers, professor of biomedical engineering, materials science and neurological surgery at Northwestern University, works as an editor at the journal that published the Faboratory’s study. He expressed excitement that a mechanically active fabric like this one could present promising options for interacting with the body and potentially aiding natural processes.

“The electronics need to kind of move naturally with daily activities, physiological processes,” Rogers said. “Maybe in the context of these mechanically active fabrics, you can take advantage of their ability to move with the body or induce motions.”

He discussed the example of providing aid to the natural beating motions of the heart. Versions of a sock-like structure surrounding the heart have been thoroughly explored in the past as a strategy for controlling irregular heartbeats and eliminating arrhythmias, but he thinks that robotic fabric could play a role in the future development of this concept.

Possible medical applications are not without their obstacles, however, as the current system runs on heat. Energy-demanding applications such as the cardiac sock would likely require scientists to turn to mechanisms other than heating, according to Rogers.

“If you increase the temperature of internal tissue by more than a couple degrees, you start doing damage, irreversible damage,” he said.

Kramer-Bottiglio’s team is acutely aware that heat poses an issue for certain applications, and Buckner has expressed interest in exploring technologies other than heat activation now that the proof of concept has been established. He is continuing his work on this project, aiming to improve the individual components so that the robotic fabric can support heavier loads, change shape faster and use even thinner fibers.

“We envision that the future will bring mass-produced rolls of robotic fabric, available for purchase, and programmable as-required to fit varied tasks,” the paper states.

Kramer-Bottiglio moved her laboratory from Purdue University to Yale in 2017.

Meggie Goodridge | meggie.goodridge@yale.edu