Spiders Inspire Soft, Recyclable Textile Fibers

Spiders may be considered household pests to some, but to scientists they are the inspiration for a new method of producing soft fibers that possess qualities well-suited for the fabrication of smart and recyclable textile fibers.

Researchers from the Department of Materials Science and Engineering at the National University of Singapore (NUS) developed a relatively simple fabrication method to make the materials, which are at the same time strong, able to stretch, and electrically conductive. In the past, creating materials with these properties together has been challenging and required complex conditions and systems.

At the same time, the process can be easily replicated at room temperature and pressure to produce new fibers, the researchers said. It also uses less solvent and energy than previous fabrication techniques, making it more environmentally friendly and efficient.

“Technologies for fabricating soft fibres should be simple, efficient, and sustainable to meet the high demand for smart textile electronics," noted NUS Assistant Professor Tan Swee Ching in a post on the NUS news site. "Soft fibers created using our spider-inspired method of spinning has been demonstrated to be versatile for various smart technology applications."

Those potential applications include weaving functional fibers into a strain-sensing glove for interactive gaming purposes or sensing temperature changes in robots to protect them from environments with extreme temperatures, he said.

Mimicking Spider Spinning

To create their process, the researchers identified two steps in the formation of spider silk—a highly efficient process that occurs in a natural environment—that they could mimic. The first is the transformation of a highly concentrated protein solution, known as a silk dope, into a strand of fiber.

Identifying that the protein concentration and interactions in the silk dope increase from synthesis to spinning, the researchers then observed that the arrangement of proteins within the dope changes when triggered by external factors. This second step—known as liquid-solid phase separation—is what helps to separate the liquid portion from the silk dope, leaving the solid part, or the spider-spun silk fibers.

The researchers recreated these two steps in the lab and developed a new spinning process they call the phase separation-enabled ambient (PSEA) spinning approach. This process spins soft fibers from a viscous gel solution—called the spinning dope—composed of polyacrylonitrile (PAN) and silver ions, or PANSion, dissolved in the common solvent dimethylformamide (DMF). The spinning dope forms into a strand of soft fiber through the spinning process when the gel is pulled and spun under ambient conditions, the researchers said.

They then exposed the PANSion gel to air, where water molecules trigger a reaction that causes the liquid portion of the gel to form drops and separate from the solid portion—called nonsolvent vapor-induced phase separation effect. When separated from the solid fiber, holding the fiber vertically or at an angle removes the liquid droplets using gravity.

“This innovative method fulfills an unmet need to create a simple yet efficient spinning approach to produce functional 1D soft fibers that simultaneously possess unified mechanical and electrical functionalities,” Tan said.

Recyclable Textile Fibers: Applications and Sustainability

The combination of the spin process and the gel allowed the researchers to fabricate soft fibers with mechanical strength, elasticity, and conductivity—all three of which the researchers tested in the lab to verify their performance. Researchers published a paper on their results in the journal, Nature Electronics.

To test the fibers in real-world applications, the team also created a few—including the aforementioned smart gaming glove—to prove its efficacy. The glove could successfully detect human hand gestures and enable a user to play simple games.

The researchers also fabricated a smart face mask that could monitor the breathing status of the wearer, something that could be used in a medical scenario to keep track of conditions such as obstructive sleep apnea.

Another key aspect of the PANSion soft fibers is their sustainability, as they can be recycled by dissolving in DMF and then converted back into a gel solution for spinning new fibers, the researchers said. In the future, the team plans to continue its work to improve this feature throughout the fibers' entire production cycle--from the raw materials to recycling the final product.