Microfluidic-directed magnetic controlling supraballs with multi-responsive anisotropic photonic crystal structures

The design and fabrication of anisotropic photonic crystal supraballs with multiple responses are highly desirable for versatile environmental sensing and flexible displaying. Herein, we developed an available strategy to construct a series of multi-responsive magnetic colloidal photonic crystal (CPC) supraballs with Janus and molecular-analogue structures. Initially, the humidity and temperature sensitive CPC supraballs were obtained via immobilization of polyacrylamide (PAM) and polyisopropylacrylamide (PNIPAM) hydrogels into the CPC structure, respectively, and CdTe/ZnS quantum dots endow the supraballs fluorescent signal under UV light. Furthermore, Fe₃O₄ nanoparticles (NPs) were served as a magnetic hemisphere to construct CPC Janus supraballs which can be subsequently assembled into three different molecular-shaped cluster particles that integrate more response types via Fe₃O₄ NPs hemisphere coalescence to a magnetic coupling center, recognizing multiple responses simultaneously that correspond the environmental altering. In addition, 2D polychromatic patterns with sensitive CPC pixels printed by automatic printing system were demonstrated, which could monitor the changes of temperature and humidity. The multi-responsive magnetic controlling supraballs and 2D patterns reveal the promising applications in environmental sensing, anti-counterfeiting and displaying.