Takahiro Sumi

Fabrication of non-close-packed colloidal monolayers by convective self-assembly using cationic polyelectrolyte-grafted silica particles

Two cationic polyelectrolytes, poly((3-acrylamidopropyl)trimethylammonium chloride) (PAPTAC) and poly(vinylbenzyl trimethylammonium chloride) (PVBTA), have been grafted on the surface of the silica particles, and then these polyelectrolyte-grafted silica particles have been applied to the convective self-assembly (CSA) process using mica substrate to prepare colloidal layers. When the PAPTAC-grafted silica particles (PAPTAC-Si) were used, we obtained the colloidal monolayers with a curious pattern composed of many wiggle beads. By the CSA process using the PVBATA-grafted silica particles (PVBTA-Si), on the other hand, we succeeded in fabricating the colloidal monolayers having a somewhat constant interparticle distance, that is, a non-close-packed (NCP) structure without using any templates. Although both particles have cationic polyelectrolytes on their surfaces, the structures of the resultant colloidal monolayers are quite different from each other, indicating that the molecular structure of the grafted polymer is crucially important for the patterning of the colloidal layers through the CSA process.

Experimental and numerical studies on the possibility of duct flow low-power generation using a butterfly wind turbine

An objective of this study is to demonstrate the validity of using a small wind turbine to recover the fluid energy flowing out of an exhaust duct for the generation of power. In these experiments, a butterfly wind turbine of a vertical axis type (D = 0.4 m) is used. The output performance is measured at various locations relative to the exit of a small wind tunnel (W = 0.65 m), representing the performance expected in an exhaust duct flow. Two-dimensional numerical analysis qualitatively agrees with the experimental results for the wind turbine power coefficient and rate of energy recovery. When the turbine is far from the duct exit (more than 2.5 D), an energy recovery rate of approximately 1.3% is obtained.