Fig. 3.

a) Scheme of the principle of in situ manipulation and monitoring of mechanical properties using photonic hydrogel. b) The hydrogel is synthesized by copolymerization of acrylate monomers in the presence of coumarin-containing acrylate and silica nanoparticles. c) Reversible photo-induced dimerization and cleavage of methyl coumarin group. d) Scheme of the reconfiguration and self-reporting of the photonic hydrogel. e) SEM and optical (inset) images of the generated hydrogel before and after reconfiguration. i) original hydrogel and after 2 (ii), 4 (iii) and 5 (iv) min illumination. As the hydrogels were freeze dried before SEM visualization, polymer networks were not visible from a top view. The center-to-center distance between the particles increases and the color of the hydrogel gradually changed from blue to red. f) Reflection spectra and the corresponding stiffness of the reconfigured hydrogels. g) Scheme of the soft and patterned light-triggered hydrogels composed of thermoresponsive polymer and gold nanorods. Gold nanorods convert NIR light-illumination into heat, leading to gel collapse. Pulsing laser results in actuating (beating) hydrogels. h-i) Immunofluorescent images showing the effect of actuation on mechanosensitive protein myocardin related transcription factor A (MRTFA) localization and fibronectin distribution. Cells in the actuating area show nuclear localization of MRTFA, whereas for cells in the non-actuating area MRTFA is in the cytoplasm (h). When cells are actuated, fibronectin secretion is more aligned (i). a)-f) Republished with permission of Royal Society of Chemistry, from [98]; permission conveyed through Copyright Clearance Center, Inc. g)-i). Adapted from [99]