Researchers at MIT have developed a programmable, actuating fibre that contracts in response to an increase in temperature, then self-reverses when the temperature decreases, without any embedded sensors or other hard components.
- The low-cost fibre named — FibeRobo—is fully compatible with textile manufacturing techniques, including weaving looms, embroidery, and industrial knitting machines, and can be produced continuously by the kilometre.
- This could enable designers to easily incorporate actuation and sensing capabilities into a wide range of fabrics for myriad applications, such as programmable compression garments that could aid in post-surgery recovery, according to the researchers.
- The fibres can also be combined with conductive thread, which acts as a heating element when electric current runs through it.
- In this way, the fibres actuate using electricity, which offers a user digital control over a textile’s form. For instance, a fabric could change shape based on any piece of digital information, such as readings from a heart rate sensor.
The researchers: The lead author of the paper on the actuating fibre is Jack Forman, a graduate student in the Tangible Media Group of the MIT Media Lab, with a secondary affiliation at the Center for Bits and Atoms.
- He is joined on the paper by 11 other researchers at MIT and Northeastern University, including his advisors, Professor Neil Gershenfeld, who leads the Center for Bits and Atoms, and Hiroshi Ishii, the Jerome B Wiesner Professor of Media Arts and Sciences and director of the Tangible Media Group.
- The research will be presented at the ACM Symposium on User Interface Software and Technology.
- This research was supported, in part, by the William Asbjornsen Albert Memorial Fellowship, the Dr. Martin Luther King Jr. Visiting Professor Program, Toppan Printing Co., Honda Research, Chinese Scholarship Council, and Shima Seiki.
- The team included Ozgun Kilic Afsar, Sarah Nicita, Rosalie (Hsin-Ju) Lin, Liu Yang, Akshay Kothakonda, Zachary Gordon, and Cedric Honnet at MIT; and Megan Hofmann and Kristen Dorsey at Northeastern University.
Morphing materials: Current shape-changing fibres have pitfalls that have largely prevented them from being incorporated into textiles beyond laboratory settings.
- One fibre, known as a shape-changing alloy, only contracts by about 5%, doesn’t self-reverse, and often stops working after a handful of actuations. Another, called a McKibben actuator, is pneumatically driven and requires an air compressor to actuate.
- The MIT researchers wanted a fibre that could actuate silently and change its shape dramatically, while being compatible with common textile manufacturing procedures. To achieve this, they used a material known as liquid crystal elastomer (LCE).
- A liquid crystal is a series of molecules that can flow like liquid, but when they’re allowed to settle, they stack into a periodic crystal arrangement. The researchers incorporated these crystal structures into an elastomer network, which is stretchy like a rubber band.
- As the LCE material heats up, the crystal molecules fall out of alignment and pull the elastomer network together, causing the fibre to contract. When the heat is removed, the molecules return to their original alignment, and the material to its original length, Forman explains.
- By carefully mixing chemicals to synthesise the LCE, the researchers could control the final properties of the fibre, such as its thickness or the temperature at which it actuates.
- They perfected a preparation technique that creates LCE fibre which can actuate at skin-safe temperatures, making it suitable for wearable fabrics. Researchers had been unable to accomplish this with other LCE fibres.
- However, the researchers discovered that making fibre from LCE resin is a finicky process. Existing techniques often result in a fused mass that is impossible to unspool.
Fabricating the fibre: Forman built a machine using 3D-printed and laser-cut parts and basic electronics to overcome the fabrication challenges. He initially built the machine as part of the graduate-level course MAS.865 (Rapid-Prototyping of Rapid-Prototyping Machines: How to Make Something that Makes [almost] Anything).
- The thick and viscous LCE resin is first heated, and then slowly squeezed through a nozzle like that of a glue gun. As the resin comes out, it is cured carefully using UV lights that shine on both sides of the slowly extruding fibre.
- If the light is too dim, the material will separate and drip out of the machine, but if it is too bright, clumps can form, which yields bumpy fibres.
- Then the fibre is dipped in oil to give it a slippery coating and cured again, this time with UV lights turned up to full blast, creating a strong and smooth fibre. Finally, it is collected into a top spool and dipped in powder so it will slide easily into machines for textile manufacturing.
- From chemical synthesis to finished spool, the process takes about a day and produces appro`ximately a kilometre of ready-to-use fibre.
- The resulting fibre, named FibeRobo, can contract up to 40% without bending, actuate at skin-safe temperatures, and be produced with a low-cost setup for 20 cents per metre, which is about one-sixtieth times cheaper than commercially available shape-changing fibres.
- The fibre can be incorporated into industrial sewing and knitting machines, as well as nonindustrial processes like hand looms or manual crocheting, without the need for any process modifications.
What They Said:
We use textiles for everything. We make planes with fibre-reinforced composites, we cover the International Space Station with a radiation-shielding fabric, we use them for personal expression and performance wear. So much of our environment is adaptive and responsive, but the one thing that needs to be the most adaptive and responsive — textiles — is completely inert.
— Jack Forman (Lead Author)
Graduate student, Tangible Media Group
MIT Media Lab
