The particle flowability can be improved by admixing particles smaller than the original particles (main particles). However, the details of this improving mechanism are not yet fully understood. In this study, we focused on effects of adhesive force distribution at each of contact points based on admixing particle coating on improving the flowability, and investigated it using discrete element method (DEM) simulation. In this simulation, we used three different surface adhesive force distribution models (non-uniform, random, and uniform models) and calculated discharge flow rates. As a result, non-uniform models had a larger discharge flow rate compared with the other models. This is because non-uniform models had a larger frequency of generating discontinuous layer, which would suppress a formation of particle arching in a bed. Thus, in a smaller particle admixing system, adhesive force distribution at each of contact points would contribute to improving the flowability.

In this study, we demonstrated the precise size control of Poly lactic-co-glycolic acid (PLGA) nanoparticles using our microfluidic device named iLiNP^®. The size of PLGA nanoparticles was able to control ranged from 30 to 120nm by the flow conditions using the iLiNP device. The iLiNP device was also applied to produce the PEG-PLGA nanoparticles and paclitaxel (PTX)-loaded PLGA nanoparticles. We confirmed the physical properties including average-size, size distribution, and encapsulation efficiency of PTX were enough to evaluate for in vivo and in vitro assays.

Various kinds of particle suspensions in organic solvents are used in a wide range of industries. Thus, characterizing interactive forces between solids in organic solvents is significant for handling such suspensions. However, while the DLVO theory well describes the interaction between surfaces in aqueous solution, the interactions between particles in non-aqueous solvents have been much less understood. In this study, we prepared silica surfaces modified with silane coupling reagents with various terminal groups and investigated the interactions between the modified particle and substrate in organic solvents by atomic force microscopy. We also conducted NMR relaxation measurements to evaluate the relationship between the interaction forces and surface-solvent molecule interactions. The repulsive forces acting over a few nanometers were measured between the surfaces when the particles disperse, whereas only van der Waals attraction was observed when the particles aggregate. This repulsive force was suggested to be the solvation force, arising from the steric hindrance of solvent molecules strongly attached to the surfaces, which was produced when the surface-solvent molecule interaction is strong. On the other hand, when van der Waals attraction dominated the interactions between the surfaces the surface-solvent molecule interaction was found out to be weak.

The accumulation of organic pollutants in surface water, groundwater, and even drinking water have raised as a serious issue in recent decades. Semiconductor-based photocatalysis has emerged as a green and sustainable approach to find remediate solutions for environmental and energy issues. However, the fast recombination rate of photogenerated charge carriers reduces the photocatalytic efficiency of photocatalysts. In this study, a hydrothermal synthesis method is proposed for preparing four types of p–n heterojunctions, BiVO₄/BiOX (X=F, Cl, Br, I). BiVO₄ is an n-type semiconductor and BiOX is a p-type semiconductor. Photocatalytic activity tests showed that the BiVO₄/BiOF has the best photocatalytic performance under visible light, and photoluminescence spectra confirmed the lowest recombination rate of photogenerated charge carriers for BiVO₄/BiOF as compared with others. The microstructure of all samples is also investigated by scanning electron microscope and transmission electron microscope.

Magnetic materials that respond to external magnetic fields are used in a wide range of fields such as magnetic resonance imaging (MRI), medical diagnostic materials, electronic materials, and catalyst. Iron oxide magnetic particles such as magnetite (Fe₃O₄) and maghemite (γ-Fe₂O₃), which have excellent magnetic properties, are generally used as constituents of magnetic materials, and various functional magnetic materials based on iron oxide magnetic particles are developed in progress. However, iron oxide magnetic particles are difficult to use as coloring materials and optical materials, since they are dark brown to black materials. In this study, we found that colorless magnetic particles can be obtained by using a polymer network in which lanthanoid elements were combined. By applying this technology, we succeeded in producing full-color magnetic particles and fluorescent magnetic particles. The produced material exhibited magnetism in the powder state and in the state of being dispersed in a solvent, and is expected to be applied as a new magnetic material.

Nanomaterials, including carbon nanotubes (CNTs), are coated by proteins in early stages of their uptake into biological systems. The protein layers around the nanomaterial surfaces are called protein corona, which determines the fate pathways and biological impacts of the nanomaterials. However, little is known about interactions of proteins with the nanomaterials during protein corona formation. In this work, we discovered that CNTs form thick and dense protein layers on their surfaces and induce oxidative stress on the proteins. The proposed protein oxidation mechanism will advance the fundamental understanding of the biological safety and toxicity of nanomaterials.

In the present study, we have studied the impact on a granular bed by a hydrogel sphere. The impact of an object will lead to the formation of a crater. The diameter of the crater is proportional to the 1/4 power of the kinetic energy of the object for low speed impact of a solid sphere. For a liquid drop impact cratering, some scaling factors (from 1/6 to 2/5) have been reported due to the complexity of a liquid drop impact phenomenon such as deformation, splashing, and penetrating granular bed. Considering only the effect of the deformation on the scaling relation, we investigated the impact cratering of a hydrogel sphere which deforms without splashing and penetrating. For spheres with high Young’s modulus, the relation of the 1/4 power law, which is reported for a solid sphere impact cratering, is observed. On the other hand, the power is smaller than 1/4 for the impact of the sphere with small Young’s modulus.

Using red blood cells (RBCs), we have fabricated functional soft particles, which exhibit not only several kinds of shapes but also biologically functional sugar chains of ABO blood group on the RBC membrane even after chemical fixation. It was found that chemical fixation of RBCs with paraformaldehyde significantly reduces the adsorption amount of bovine serum albumin on an RBC, but hardly affects that of lectins (i.e., proteins that recognize blood type sugar chains).

First-principles calculations were conducted to study the possibility of the formation of SnTiO₃. Nanocluster models were used, and BaTiO₃ and SnTiO₃ were studied. SnTiO₃ was stabilized with Sn rich surface similar to the BaTiO₃. Also, SnTiO₃ has smaller surface energy than that of BaTiO₃, suggesting the possibility of the formation of nanoparticles of SnTiO3 and stabilization of the unstable structure with nanometer-size. As a result of nanoparticle synthesis of BaTiO₃, Ba deficient structure was elucidated. Under the condition, the synthesis of Sn-Ti composite oxide was studied.

In this study, to clarify the mechanism of the permeation and collection through a filter, a direct numerical simulation model for multi-phase flows was newly developed. We extend this model to apply air filter and coalescer. To represent a realistic microporous structure inside the filters during simulation, a numerical method that coordinates the filter structure obtained by X-ray CT imaging with computational fluid dynamics is developed. The predictions of filter pressure drop from our numerical method were quantitatively in good agreement with the experimental measurements and the empirical equations previously reported. Finally, we demonstrated that the present method can be easily extended to multiphase flow simulations.