Active matter often exhibits ordered collective motion, such as in bacterial colonies or swarms of fish and birds. Understanding the mechanisms underlying the complicated collective behaviors is significant to develop innovative chemical systems. We discovered that Pt catalytic particles with simpler structures exhibit a unique collective motion, that is, repetitive cluster formation and disintegration in an aqueous ethanol solution. In this study, the collective behavior of Pt particles is demonstrated in mixtures containing inert particles. Two distinct types of cluster formation were observed by varying the mixing ratio of the Pt and Au particles: Pt/Au mosaic-like clusters and Pt/Au core–shell clusters. In contrast, no Pt/silica cluster formation was observed in the silica particles mixed with Pt particles. In the Pt/Au core–shell clusters observed in this study, the thickness of the Au particle shell could be controlled by adjusting the concentration of the Au particle. This finding suggests that the spatial separation of Pt and Au particles can be realized under controlled conditions.

As grinding progresses, powders exhibit high surface activity due to the generation of ions and radicals, and interfacial effects become pronounced. Mechanochemical reactions that effectively utilize this surface activity have been applied to the synthesis of functionalized powders. In this study, a mechanochemical polymerization process was carried out continuously modifying the surface of silica particles by grinding silica sand in the presence of methyl methacrylate (MMA) using a dry bead mill. The effects of grinding conditions on the MMA conversion, particle size distribution, specific surface area, and chemical composition were investigated. As a result, the possibility of continuously producing surface-modified particles with polymer coatings accompanied by fine grinding was demonstrated. Furthermore, it was confirmed that optimizing the milling atmosphere and grinding conditions is crucial for improving the efficiency of polymer-modified powder production in this process.

3D printing has emerged as a promising technology for the production of personalized medicines, enabling freeform design and on-demand manufacturing. Selective laser sintering (SLS) is a solvent-free powder bed fusion technique capable of simultaneously fabricating dosage forms and inducing drug amorphization. However, the optimization of printing parameters and the reuse of powder materials remain key challenges for pharmaceutical applications. In this study, printlets containing either acetaminophen or indomethacin were fabricated using an SLS 3D printer with Kollidon^® VA64 as a thermoplastic polymeric excipient. The effects of SLS process parameters on printlet formability and drug dissolution were evaluated. The results demonstrated that printing temperature strongly influenced formability, with optimal values varying between formulations. Although the reuse of powder was not feasible due to physicochemical changes in the drug upon heat exposure, high manufacturing efficiency was achieved by maximizing the number of printlets produced per batch. Furthermore, indomethacin was successfully amorphized during the printing process, leading to a marked improvement in its dissolution behavior. These findings suggest that SLS 3D printing can serve as a one-step manufacturing platform for preparing amorphous solid dispersions and enabling flexible design of dosage forms for poorly water-soluble drugs.

Recent advances in bead mill design have been achieved through optimization using the Discrete Element Method (DEM). This is because the impact energy of beads calculated by DEM is well correlated with the actual grinding performance of bead mills. However, wear is inevitable in bead mills, leading to a decline in grinding performance and making it difficult to maintain the effectiveness of the optimized shape over time. In this study, we propose a shape optimization system that accounts for wear. The proposed system integrates the Design of Experiments (DOE) for analyzing shape parameters and the Interface Capturing Wear Model (ICWM) for accurate and robust wear simulation. The effectiveness of optimized bead mill is validated through comparison with actual grinding experiments.

The goal of this research is to prepare polymethyl methacrylate (PMMA) nanoparticles with an average particle diameter of less than 100 nm in which a functional dye that absorbs near-infrared light is immobilized. In the experimental conditions used in this study, the liquid-in-drying method was employed to prepare the nanoparticles by dissolving the polymer as the wall material and the functional dye in an organic solvent and dispersing the O/W emulsion in water. As a result, the particle size tended to decrease as the concentration of nonionic surfactant added to the dispersed phase was increased, and nanoparticles with functional dyes below 100 nm could be prepared under conditions of 15 wt% or higher. However, as the surfactant concentration increased, the functional dye content decreased. In the dispersion stability tests of the prepared nanoparticles had a high dispersion stability under a static condition for 7 days expect for the nanoparticles prepared with Tween80 concentration of 1 wt%.