A polydimethylsiloxane (PDMS) microfluidic chip with well-interconnected microfibrous channels was fabricated by using an electrospun poly­(ε-caprolactone) (PCL) microfibrous matrix and 3D-printed pattern as templates. The microfiber-templated microfluidic chip (MTMC) was used to produce nanoscale emulsions and spheres through multiple emulsification at many small micro-orifice junctions among microfibrous channels. The emulsion formation mechanisms in the MTMC were the cross-junction dripping or Y-junction splitting at the micro-orifice junctions. We demonstrated the high throughput and continuous production of water-in-oil emulsions and polyethylene glycol-diacrylate (PEG-DA) spheres with controlled size ranges from 2.84 μm to 83.6 nm and 1.03 μm to 45.7 nm, respectively. The average size of the water droplets was tuned by changing the micro-orifice diameter of the MTMC and the flow rate of the continuous phase. The MTMC theoretically produced 58 trillion PEG-DA nanospheres per hour without high shear force. In addition, we demonstrated the higher encapsulation efficiency of the PEG-DA microspheres in the MTMC than that of the microspheres fabricated by ultrasonication. The MTMC can be used as a powerful platform for the large-scale and continuous productions of emulsions and spheres.

The self-organization of colloidal nanoparticles into programmed suprastructures is an important research area in various disciplines of nano, colloid, and polymer sciences. However, despite the recent advances in their fundamental understanding and practical applications, the selforganization of organic-free inorganic nanoparticles remains unexplored. Herein, we present the controlled organization of oppositely charged allinorganic nanoparticles through the electrostatic interaction and the colloidal behaviors of organized suprastructures. Depending on the charge states of the assembled suprastructures, three different phases, including patchy, patchy bridged, and fully coated particles, are identified, enabling the construction of the phase diagram with nanoparticle concentrations. Especially, the fully coated particles exhibit unexpected colloidal stability through the action of nanoparticles as surface stabilizers to induce the overcharged surface state; thus, we propose the concept of "nanoligands". It is demonstrated that this concept can be extended to a wide range of material combinations, including semiconducting, metallic, and oxide nanoparticles. The currently developed approach will enable the chemical designing of self-organized nanostructures.

Poly( -caprolactone) (PCL)-based polyurethane (PU) foam scaffolds with different mechanical properties are fabricated using a gas foaming technique to use as porous substitutes for ear or bone with cartilage. PCL diol or triol is used as a polyol in PU foam for biocompatibility and biodegradation, with an aqueous gelatin solution as a blowing agent. The highly porous inner and outer structures of the scaffolds are developed by employing a silicone surfactant and sulfuric acid, respectively. The PU scaffolds prepared by PCL diol show ductile and flexible properties, whereas the PU scaffolds prepared by PCL triol exhibit high compression strength. In vitro test reveals the low toxicity of the PU scaffolds and the high ALP activity of MC3T3-E1 cells in the PU scaffold prepared by PCL triol. By taking advantage of the difference in mechanical properties, customized PU scaffolds with ear or bone shapes are fabricated using a silicone mold. The PU scaffolds with two compartments of PCL diol and triol (corresponding to cartilage and bone, respectively) are fabricated as a substitute for bone with cartilage. It is believed that the PU scaffolds with highly porous structure and controlled mechanical properties have wide potential application for tissue engineering.

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Halide perovskite solar cells have been attracting tremendous attention as next-generation solar cell materials because of their excellent optical and electrical properties. Formamidinium lead tri-iodide (FAPbI3) exhibits the narrowest band gap among lead iodide perovskites and shows excellent thermal and chemical stability, also. However, the large-area coating of FAPbI3 needed for commercialization has not been successful because of the instability of the black phase of FAPbI3 at ambient temperature. This study presents a compositional engineering direction to control the polymorph of the FAPbI3 thin film for the shear coating processes, without halide mixing. By adopting a hot substrate above 100 oC, our shear coating process can produce the black phase FA-based halide perovskites without halide mixing. We carefully investigate the Cs-FA and MA-FA mixed lead iodide perovskites’ phase stability by combining the study with thin-film fabrication and ab initio calculations. Cs-FA mixing shows promising behaviors for stabilizing α-FAPbI3 (black phase) compared with MA-FA. Stable FA-rich perovskite films cannot be achieved via shear coating processes with MA-FA mixing. Ab initio calculations revealed that Cs-FA mixing is excellent for inhibiting phase decomposition and water incorporation. This study is the first report that FA-based halide perovskite thin films can be made with the shear coating process without MA-Br mixing. We reveal the origin of the stable film formation with Cs-FA mixing, and present future research directions for fabricating FA-based perovskite thin films using shear coating.