Scalable Wet Spinning of Graphene Liquid Crystalline Elastomer Composite Filaments for Responsive Soft Actuators

Conventional haptic and intelligent systems are designed to complete complex tasks through mechanical and pneumatic systems that leverage rigid materials, resulting in systems that can be heavy and nonadaptive to the environment, especially in wearable contexts. Liquid crystal elastomers (LCEs) have shown to be a promising material candidate for the development of soft, elastic environmentally-responsive actuators and have been extensively researched in their application as an artificial muscle actuator and in smart textiles. To facilitate the application of LCEs into haptic platforms, the scalable production of LCEs as filaments is critical. LCEs pose as a promising candidate to apply conventional and commercially-viable textile manufacturing processes such as wet spinning due to its polymeric nature, a processing technique commonly used for popular liquid crystalline polymers such as Nomex® or Kevlar®. Here, we present a fast and reliable wet-spinning fabrication method for the scalable fabrication of graphene LCE composite filaments under mild processing conditions. We develop a double diffusion mechanism that allows for rapid crosslinking of a spinning dope into tangible filaments due to solvent exchange and high catalyst influx. We report the scalable one-step production of continuous polydomain graphene-LCE filaments with fabrication speeds up to 4500 m/hr. With the inclusion of graphene, we showcase morphological and mechanical optimization of the LCE filaments to enable thermo- and NIR-responsive stimuli for robust actuation. The wet-spun graphene-LCE composite filaments are notably capable of fabrication in a broad range of diameters (137 to 1128 μm) and can generate actuation stresses and strains up to 3.66 MPa and 44% in 3 s. Using filaments manufactured across the diameter range, we showcase the versatility of the processing technology by using the filaments as artificial muscles, a popular application of LCEs. We envision that the scalable wet-spinning production of polydomain graphene LCE composite filaments across a range of diameters will open new opportunities to design smart textiles and soft robotics.