Photothermal Actuation of Thick 3D‐Printed Liquid Crystalline Elastomer Nanocomposites

Liquid crystalline elastomers (LCEs) are stimuli‐responsive materials that transduce an input energy into a mechanical response. LCE composites prepared with photothermal agents, such as nanoinclusions, are a means to realize wireless, remote, and local control of deformation with light. Amongst photothermal agents, gold nanorods (AuNRs) are highly efficient converters when the irradiation wavelength matches the longitudinal surface plasmon resonance (LSPR) of the AuNRs. However, AuNR aggregation broadens the LSPR which also reduces photothermal efficiency. Here, the surface chemistry of AuNRs is engineered via a well‐controlled two‐step ligand exchange with a monofunctional poly(ethylene glycol) (PEG) thiol that greatly improves the dispersion of AuNRs in LCEs. Accordingly, LCE‐AuNR nanocomposites with very low PEG‐AuNR content (0.01 wt%) prepared by 3D printing are shown to be highly efficient photothermal actuators with rapid response (>60% strain s−1) upon irradiation with near‐infrared (NIR; 808 nm) light. Because of the excellent dispersion of PEG‐AuNR within the LCE, unabsorbed NIR light transmits through the nanocomposites and can actuate a series of samples. Further, the dispersion also allows for the optical deformation of millimeter‐thick 3D printed structures without sacrificing actuation speed. The realization of well‐dispersed nanoinclusions to maximize the stimulus‐response of LCEs can benefit functional implementation in soft robotics or medical devices. A two‐step process to functionalize gold nanorods (AuNRs) with poly(ethylene glycol) (PEG) thiol results in improved AuNR dispersion in liquid crystalline elastomers (LCEs). Improved dispersion and low PEG‐AuNR loadings in 3D‐printed LCE‐AuNR enable efficient photothermal heating, rapid actuation with contractile strain rates exceeding 60% s−1, and complex photothermal deformation of 1 mm thick 3D‐printed structures.