Figure 4.

Microscopic in-situ observation of the light-induced SASS response. (a) Schematic of the microscope and sample set-up for in-situ observation of SASS. Irradiation with a 405 nm laser initiates photothermal heating, and remodels MNP organization. (b) Images of aligned MNPs in the responsive layer captured upon initiation of photothermal heating (0 s), at the end of heating (13.9 s), and at the end of cooling (27.8 s). (c) Time-lapse images of aligned MNPs in the responsive layer collected during photothermal heating with a 405 nm laser and cooling with the laser off. (d) and (e) show plots of line-scans for Fe₃O₄@SiO₂ nanoparticles (~3 nM), and SiO₂ nanoparticles (~3 nM) embedded within pNIPAM hydrogels during relaxation following 405 nm excitation for 13.9 s.