Cross-linking dependent performance analysis in liquid crystal network actuators

Liquid crystal network (LCN) actuators are promising materials for soft robotics and artificial muscles because of their programmable and reversible shape deformations. However, optimizing their performance for specific applications requires a clear understanding of how network composition affects actuator output. This work investigates splay-aligned LCN actuators with high crosslink density (RM-HI) and low crosslink density (RM-LO) and identifies a clear trade-off between blocking force and actuation speed. Our results demonstrate that the highly crosslinked RM-HI actuators generated a substantially higher average blocking force of 68.5 mN compared to 39.0 mN for RM-LO. Conversely, the lower crosslinked RM-LO films exhibited greater free-bending displacement (16.5 mm vs. 13.6 mm) and significantly faster actuation and relaxation dynamics. Under cyclic testing, both formulations maintained stable macroscopic actuation and blocking-force output over the tested cycles. While prolonged cycling induced an increase in surface roughness that altered the apparent optical absorptance via scattering, it did not degrade the mechanical functionality of the actuators. Ultimately, this work provides quantitative, energy-based design guidelines for tailoring LCN actuator performance to application-specific requirements.