Near-Infrared Light-Driven Microgrooved UCNPs/Azobenzene-LCE Actuators and Substrates for Cardiomyoblast Alignment

Photoisomerization-based liquid crystal elastomer (LCE) actuators offer precise spatiotemporal control over mechanical deformation, yet their reliance on ultraviolet (UV) irradiation limits biomedical applicability due to phototoxicity and poor tissue penetration. Herein, we report an 808 nm near-infrared (NIR) light-driven photoisomerization actuator based on azobenzene-cross-linked LCEs (Azo-LCEs) integrated with NaYF₄:Yb/Tm@NaYF₄:Yb/Nd@NaYF₄ core-shell-shell upconversion nanoparticles (CSS-UCNPs). The Nd³⁺-sensitized CSS-UCNPs convert 808 nm NIR light into UV/blue upconversion emissions (345-476 nm), driving trans-to-cis isomerization of azobenzene units and inducing macroscopic bending of the LCE films. To evaluate the actuation performance, the UCNPs/Azo-LCE films were tested under continuous-wave 808 nm irradiation for 20 s at power densities of 4-24 W cm^-2, reaching a maximum bending angle of 42.8 ± 2.6° at 24 W cm^-2 and exhibiting stable cyclic actuation over 50 cycles at 16 W cm^-2. For biologically relevant operation, thermal assessment at lower irradiation intensities revealed only a limited temperature rise in the culture medium under 4-8 W cm^-2 irradiation (ΔT = 2.29-4.36 °C), with no obvious cumulative heating during cyclic operation (20 s on/20 s off, 50 cycles). In addition, microgroove-patterned UCNPs/Azo-LCE substrates supported the adhesion and spreading of rat cardiomyoblast cells (H9c2) and guided groove-width-dependent uniaxial alignment. This work establishes a strategy for 808 nm-excited photoisomerization-driven LCE actuation and highlights its potential as an NIR-addressable soft actuator platform for future studies of dynamic cell-guidance, while operating with a modest thermal burden under the tested conditions.