Researchers have created a low-cost fiber that shrinks when heated and regains its shape when heat dissipates. The deformable fiber is compatible with existing textile machinery and does not rely on sensors or other hardware, so it can be used in a variety of ways. Researchers have been working for some time to produce deformable fibers that can be incorporated into textiles, which could be used for a range of purposes from warmth to padding aircraft. But many fibers require hardware, making them impractical for use outside the lab.
Now, researchers at MIT and Northeastern University have developed a low-cost actuation fiber called FibeRobo that changes shape in response to temperature changes and is compatible with existing textile manufacturing machinery, meaning it has the potential for real-world applications.
"We use textiles for everything. We build airplanes with fiber-reinforced composites, we cover the International Space Station with radiation-resistant fabrics, and we use them to express personal style and performance clothing," said Jack Forman, lead author of the study. "So many things in our environment are adaptable and responsive, but the things that need to be adaptable and responsive the most - textiles - are completely inert."
To create a fiber that could silently actuate and change shape while being compatible with common textile manufacturing procedures, the researchers looked to liquid crystal elastomers (LCEs). Liquid crystals are a series of molecules that can flow like a liquid, but when they are allowed to settle, they pack into a crystalline arrangement.
They integrated these crystal structures into a stretchable elastomer network. When heat is applied to LCE, the crystals lose alignment and pull the elastomer together, causing the fibers to shrink. When the heat is removed, the molecules return to their original arrangement.
Fibers are made by slowly extruding the heated LCE resin through a nozzle and curing it with ultraviolet light. The light has to be just right. Too little light can cause the material to separate and drip; too much light can cause the material to clump. The fibers are then dipped in oil to give them a smooth coating and cured again with strong UV light to create strong, smooth fibers. Finally, the fibers are collected onto a spool at the top and dipped in powder so they can be easily slipped into a textile manufacturing machine.
"We can turn a lot of knobs," Forman said. "It took a lot of effort to develop this process from scratch, but in the end it gave us a lot of freedom in producing the fibers".
The entire process, from chemical synthesis to finished spool, takes about a day and produces about a kilometer (0.6 miles) of ready-to-use fiber. The fiber, which the researchers named FibeRobo, costs 20 cents per meter (3.3 feet) to produce, making it about 60 times cheaper than commercially available shape-changing fibers. It can shrink by 40% without bending, but the skin-safe version only shrinks by 25%.
The fiber can be used on industrial sewing machines, knitting machines and non-industrial handlooms, as well as in crochet without any modifications to the process. To test FibeRobo's capabilities, researchers used an industrial knitting machine to create a compression jacket for Forman's dog that "cuddles" the pet via a smartphone's Bluetooth signal.
They also used it to create an embroidered adaptive sports bra that tightens when the user starts moving.
The researchers plan to make FibeRobo's chemical components recyclable or biodegradable and simplify the polymer synthesis process so that users without laboratory expertise can make their own.
"Ultimately, you don't want a mythical fabric," Forman said. "What you want is a fiber that when you use it, it belongs in a collection of materials - you can use it like any other fiber material, but it has a lot of exciting new capabilities."
The researchers hope that in the future, people will be able to buy a FibeRobo at a craft store like a ball of yarn and use it to make their own shape-shifting products.
The research will be presented at the 36th ACM Symposium on User Interface Software and Technology in October 2023. The video below, produced by MIT, demonstrates FibeRobo's capabilities.