A biomimetic process to make soft fibers for smart textiles

August 1, 2023 | By Gerald Ondrey

For intelligent textiles to function effectively, they need to be strong, stretchable and electrically conductive. However, fabricating fibers that possess these three properties has been challenging.

Drawing inspiration from how spiders spin silk to make webs, an international team of researchers has developed a method of producing soft fibers that possess these three key properties. The study — led by assistant professor Tan Swee Ching from the Dept. of Materials Science and Engineering under the National University of Singapore (NUS; www.nus.sg) College of Design and Engineering — was reported in a recent issue of Nature Electronics.

Conventional spinning methods to fabricate synthetic fibers require high pressure, high energy input, large volumes of chemicals, and specialized equipment. Moreover, the resulting fibers typically have limited functions. In contrast, the spider-silk-spinning process forms strong and versatile fibers at room temperature and pressure. Two unique steps in spider-silk formation were identified that the team could mimic. The first is the change of a highly concentrated protein solution (silk dope) into a strand of fiber. The second step identified was that the arrangement of proteins within the dope changes when triggered by external factors to help separate the liquid portion from the silk dope, leaving the solid silk fibers. The team recreated the two steps and developed a new spinning process known as the phase separation-enabled ambient (PSEA) spinning approach.

The soft fibers were spun from a viscous gel solution comprised of polyacrylonitrile (PAN) and silver ions (PANSion) dissolved in dimethylformamide. When the gel is pulled and spun under ambient conditions, the soft fiber forms. When exposed to air, water molecules in the air cause the liquid portion of the gel to separate from the solid portion of the gel — a phenomenon known as the nonsolvent vapor-induced phase-separation effect. The droplets are simply removed by gravity.