The first microfluidic synthesis of ionomer‐based bifunctional Janus supraballs possessing two distinct magnetic‐nanoparticle‐dropped and quantum dots–polymer hemispheres within an anisotropic structure is reported. Based on such Janus supraballs with stable fluorescence and superparamagnetism, a magnetoresponsive fluorescent switch is developed to realize free‐writing under a magnetic field. This is a promising, simple way to fabricate novel flexible bead displays.

The design and development of Janus suprabeads (JSs) with multiple responses are highly desirable in the fabrication of functional nanomaterials. In this work, we report a triphase microfluidic strategy for the construction of JSs with temperature-magnetism-optics triple responses. Initially, macromonomer poly(methacrylic acid) (PMAA) obtained via catalytic chain transfer polymerization (CCTP) was grafted onto the polystyrene (PS) colloidal photonic crystals (CPCs) surface. Because abundant carboxylic acid groups in PMAA could coordinate cadmium ions for in situ production of fluorescent CdS quantum dots (QDs) after introducing sulfur ions, the as-prepared JSs were endowed with favorable optical properties. Meanwhile, the as-prepared Cd(2+)/PS CPCs were employed as a template to build JSs with temperature-magnetism sensitivity via the introduction of magnetic Fe3O4 and hydrogels. Finally, the fluorescence pattern was easily performed by using chalcogenides as "ink" to write on the pad, in which in situ reaction mechanism was involved in the response. The multiple responsive JSs show promising applications in sensor, display, and anticounterfeit fields.

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We report an alternative pathway for the facile fabrication of tunable colloidal photonic crystal (TCPC) hydrogel supraballs via a simple microfluidic device for the first time. The TCPC hydrogel supraballs immobilized the CPC structure into a PAm hydrogel, which has properties suitable for humidity sensing and volume phase transition behavior. Thus, the as-prepared TCPC hydrogel supraballs can monitor a very broad humidity range by obvious color changes rather than traditional volume changes suffering from a time-consuming gravimetric measurement. The color changes are reversible and durable corresponding to humidity sensitivity, and cover almost the whole visible spectrum. More interestingly, the optical stopband of the spherical TCPCs is angle-independent on the curved surface. Furthermore, this procedure also provides a new insight into the creation of novel micro-scaled stimuli-responsive CPC devices.

The predictable assembly of colloidal particles into a programmable superstructure is a challenging and vital task in chemistry and materials science. In this work, we develop an available magnetic-directed assembly strategy to construct a series of molecular-analogue photonic crystal cluster particles involving dot, line, triangle, tetrahedron, and triangular bipyramid configurations from solid-liquid Janus building blocks. These versatile multiplex molecular-analogue structural clusters containing photonic band gap, fluorescent, and magnetic information can open a new promising access to a variety of robust hierarchical microstructural particle materials.