Super-Elastic Magnetic Structural Color Hydrogels.

Structural color hydrogels are promising candidates as scaffold materials for tissue engineering and for matrix cell culture and manipulation, while their super-elastic features are still lacking due to the irreconcilable interfere of the precursor and the self-assembly unit. This hinders many of their practical biomedical applications where elasticity is required. Herein, hydrophilic and size-controllable Fe3 O4 @poly(4-styrenesulfonic acid-co-maleic acid) (PSSMA)@SiO2 magnetic response photonic crystals are fabricated as the assembly units of the structural color hydrogels by orderly packing of core-shell colloidal nanocrystal clusters via a two-step facile synthesis approach. These units are capable of responding instantaneously to an external magnetic field with resistance to interference of ions, thus, by integrating super-elastic hydrogels, super-elastic magnetic structural color hydrogels can be achieved. The structural color arises from the dynamic ordering of the magnetic nanoparticles through the contactless control of external magnetic field, allowing regional polymerization of hydrogels via changing orientation and strength of external magnetic field. These regionally polymerized super-elastic magnetic structural color hydrogels can work as anti-counterfeiting labels with super-elastic identification, which may be widely used in the future.