In behavior can be explained when assuming that the highly swollen pNIPAAm-based hydrogel nanostructure wraps around the whole AuNP in its swollen state. When increasing temperature T above the LCST, the hydrogel compacts at the AuNP walls where it was attached by the plasmonically enhanced intensity of the NIR fs laser beam (Figure ). This effect is accompanied by an increased surface mass density and higher refractive index of the hydrogel on walls perpendicular to the polarization (||) of the writing beam. On the surface of walls parallel to the fs NIR beam polarization (⟂) where the polymer network is not attached, it retracts towards the plasmonic hotspots and is replaced by water with a lower refractive index of nH2O = 1.33.