Liquid crystal elastomers (LCEs) are one promising actuator materials due to their reversible and anisotropic deformation during the phase transition. However, for high strength actuators for applications such as robotics, it is important to increase the elasticity of the LCEs and make them amenable to light and electrical actuation. Here, we demonstrate fabrication of meter long LCE filaments from diacrylate LC monomer and thiol-terminated LC oligomer, showing light and electrical responsiveness based on photothermal and electrothermal effect, respectively. The LCE filaments were produced by extruding LC mixtures through a syringe pump, followed by rapid UV crosslinking via the thiol-acrylate click reaction, allowing for immediate locking of the uniaxial alignment along the filament. The wide-angle x-ray scattering (WAXS) measurement showed that addition of needle-shaped cellulose nanocrystals (CNCs) improved the alignment of LC molecules along the filament long axis. As a result, it enhanced the elasticity of the filament: filaments with 4 wt% CNCs can withstand ~15% more strain compared to the pristine ones. When adding multi-wall carbon nanotubes (MWCNTs) into the system, the modulus of filaments was improved by an order of magnitude as measured by the dynamical mechanical analysis (DMA) tests. As a result, the composite filaments demonstrate high work capacity, up to 38 J/kg (vs. 2.3 J/kg from the patterned films), which is comparable to 40 J/kg from human muscles.  The highly elastic LCE filaments with well controlled molecular alignment could be embedded in a robotic hand for sequential and programmed actuation of the fingers with dexterity and adaptivity upon exposure to light or electric field.<br/>

Highly elastic liquid crystal elastomer-carbon nanotube composite filaments as programmed actuators

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.