Thermo-Mechanically Recyclable Smart Textiles from Circularly Knitted Liquid Crystal Elastomer Fibers

Liquid crystal elastomer (LCE) fiber actuators are promising candidates for smart textiles owing to their reversible large-stroke actuation and high aspect ratios. However, current LCEs require ultraviolet (UV) curing and are not recyclable. In addition, research is mainly focused on flat knitted thermo-responsive textiles. Here, a scalable recycling route for smart LCE textiles is developed by melt-extruding a thermoplastic LCE containing a near-infrared photothermal dye. The LCE fibers exhibit ∼30% reversible actuation strain and display light-driven rolling motions with left- or right-turning trajectories according to their programmed twist handedness. Using commercial knitting machines, multi-material plain- and rib-knit textiles are fabricated that exhibit in-plane contraction and out-of-plane deformations including bending and twisting under thermal and photo stimuli. Circularly knitted tubular structures exhibit reversible contraction in both radial and axial directions, reaching approximately 16% in outer diameter, 19% in inner diameter, and 14% in length, enabling applications in autonomous climbing, controlled liquid release, and micro pumping. Finally, thermo-mechanical recycling yields recycled fibers and both flat and circularly knitted textile structures with nearly unchanged actuation performance and comparable mechanical properties, demonstrating robust recyclability. Our results demonstrate the creation of smart textiles that are simultaneously intelligent in function and sustainable in design.