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Colloidal crystals (CCs) are ordered arrays of monodisperse colloidal particles. Because of the presence of a periodic superlattice of colloids and voids, CCs bear many unique structures and fascinating properties which are distinctly different from those of standard crystals with atoms, ions or molecules as repeating subunits. The research on CCs has surprisingly blossomed during recent decades, and many practical materials based on CCs with potential applications in photonic devices, material science and biomedical engineering have been generated. In this review, we give a systematic, balanced and comprehensive summary of the main aspects of CCs related to their preparation and application, and propose perspectives for the future developments of CCs.

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Pebax-1657 is known as a promising polymeric membrane material for CO 2 /N 2 and CO 2 /H 2 separation. In order to further improve its gas separation performance and reinforce the membrane, different fillers including silica nanoparticles, polystyrene (PS) colloids, and carbon nanotubes (CNTs) were incorporated into the polymer matrix to form nanocomposite membranes. The nanocomposite membranes of Pebax-1657/silica and Pebax-1657/PS colloid had a decreased CO 2 permeability and selectivity over N 2 or H 2 compared to the pure Pebax-1657 membrane, while the Pebax-1657/CNT nanocomposite membranes had an increased CO 2 permeability, retaining similar CO 2 /N 2 or CO 2 /H 2 selectivity compared to the pure polymer membrane. The CO 2 permeability increased with increasing CNT content and reached a maximum at 5 wt % CNTs. The CNT-enhanced gas permeability was attributed to the increase in gas diffusivity. The tensile modulus of Pebax-1657 increased 43% after adding 5 wt % single-wall CNTs (SWNTs), and increased 24% after adding 5 wt % multi-wall CNTs (MWNTs). Thus, it is feasible to add CNTs to Pebax-1657 membranes for improved mechanical strength and gas separation performance.

A tough and electro-responsive hydrogel actuator exhibits fast, cyclic and bidirectional bending behavior.