## 3 Shape-Memory Polymer Nanocomposites (SMPNCs)
### Metal-Based Nanocomposites
#### 3.1.4 Tungsten Oxide Nanowire Nanocomposites  
Tungsten oxide nanocrystals (WO\({}_{3-\mathrm{x}}\)) exhibit broad absorption across the UV-vis-NIR region due to their intramolecular charge transfer and localized surface plasmon resonances (LSPR) absorption [122]. Their photothermal conversion efficiency is notably high, approximately 28.1%, which is comparable to carbon nanotubes (28%) and surpasses the efficiencies of AuNPs at 11% and reduced graphene oxide (rGO) at 12%, as previously reported [123]. Diverse nanostructures of WO\({}_{3-\mathrm{x}}\), including nanofibers, nanowires, and spherical particles, have been prepared with tunable sizes. Among these, WO\({}_{3-\mathrm{x}}\) nanowires display superior NIR light absorption, highlighting their potential for advanced photothermal applications [124]. [PERSON] et al. introduced multi-photoresponse SMP composites and chiral actuators incorporating oligo(ethylene glycol) (OEG)-modified W\({}_{18}\)O\({}_{49}\) nanowires into cross-linked polyethylene glycol diacrylate (cPEGDA) matrices (Figure 12a) [72]. The integration of OEG-modified W\({}_{18}\)O\({}_{49}\) nanowires facilitated chemical cross-linking through acrylate groups for shape fixty and utilized crystalline PEG segments as the reversible phase for shape memory [72]. The presence of OEG ligands on the W\({}_{18}\)O\({}_{49}\) surface enhanced compatibility with cPEGDA via hydrogen bonding, ensuring even dispersion of nanowires and maintaining high crystallinity at loadings up to 4.0 wt.%. The cPEGDA/W\({}_{18}\)O\({}_{49}\) nanocomposites exhibited rapid temperature increases due to the efficient photothermal conversion of W\({}_{18}\)O\({}_{49}\) nanowires and effective heat transfer to the polymer matrix. As illustrated in Figure 12b, a composite with 2.0 wt.% nanowire loading reached a surface temperature of 74 \({}^{\circ}\)C under 365 nm UV light within one minute. Under 808 nm NIR laser irradiation (1.6 W cm\({}^{-2}\)), the temperature escalated to 167 \({}^{\circ}\)C in 20 s and 214 \({}^{\circ}\)C in one minute. Similarly, under a 980 nm NIR laser (1.6 W cm\({}^{-2}\)), the temperature reached 161 \({}^{\circ}\)C in 20 s, highlighting their potential for rapid and precise thermal actuation. [PERSON] et al. developed remotely and spatially controllable shape-shifting characteristics in SMP composites upon a laser-induced temperature gradient [125]. These composites were synthesized through a thiol-ene Michael addition reaction, using acrylate-terminated polycaprolactone (PCLDA) and a four-arm cross-linker to integrate OEGy-modified W\({}_{18}\)O\({}_{49}\) nanowires as photothermal agents. The crystalline PCL phase within the composite underpins the SME, while the OEGy-W\({}_{18}\)O\({}_{49}\) nanowires serve to absorb light and convert it into heat [125]. Upon exposure to a 100 mW/cm\({}^{2}\) laser, the composites rapidly exceed the melting temperature (T\({}_{\mathrm{m}}\)) of PCL, with the equilibrium temperature rising in tandem with the OEGy-W\({}_{18}\)O\({}_{49}\) content at a constant laser intensity. A direct relationship was observed between laser intensity and peak temperature, which varied from 92.3 \({}^{\circ}\)C to 175.2 \({}^{\circ}\)C as the laser intensity increased from 0.1 to 1 W/cm\({}^{2}\). Following laser discontinuation, the composites cooled down to ambient temperature. These materials exhibited excellent  
Figure 11: (**a**) Diagram illustrating the conventional preparation methods for SMP surfaces with micro-cone arrays; (**b**) the transfer of droplets without any loss during both the “captured” and “detached” stages. Reproduced with permission from ref. [121]. Copyright 2020 American Chemical Society. thermally induced shape-memory behavior, with shape fixity (R\({}_{f}\)) and shape-recovery (R\({}_{r}\)) ratios of 97.1% and 96.3%, respectively.