Liquid crystal elastomers for orthopedic applications: Comparative analysis of formulations and viscoelastic...

Osteoarthritis (OA) is a leading cause of disability worldwide and often necessitates surgical interventions such as joint fusion or replacement when cartilage degeneration becomes severe. Conventional implants composed of cobalt chromium (CoCr), ceramics, or ultra-high molecular weight polyethylene (UHMWPE) provide durability but lack viscoelastic compliance, leading to stress mismatch, wear, and long-term complications. Hydrogels and synthetic cartilage substitutes have been explored as alternatives; however, their insufficient mechanical strength and inconsistent clinical outcomes limit their use in whole-surface cartilage replacement. These limitations highlight the need for new materials that combine mechanical durability with cartilage-like functionality. Liquid crystal elastomers (LCEs) are emerging candidates as a joint replacement material due to their soft elasticity, rate-dependent viscoelasticity, and capacity for energy dissipation, making them particularly well suited for cartilage replacement applications. In this study, we evaluated three LCE formulations (LCE15, LCE30, and LCE45) spanning a range of stiffness and compliance to identify their suitability for joint applications. A range of mechanical characterization was performed, including Young's modulus, compressive modulus, equilibrium modulus from creep and stress relaxation, and dynamic modulus at physiological frequency. Across tests, LCE15 and LCE30 exhibited properties at or below the lower bounds of articular cartilage, indicating potential suitability in low-load applications. By contrast, LCE45 demonstrated consistently robust performance across all parameters, closely matching or exceeding native cartilage values. These results identify LCE45 as the most promising formulation for cartilage replacement and motivate further investigations into its durability, frictional behavior, and performance under physiologically relevant loading conditions.