Papers by Author: Ryo Yoshida

Abstract: We have developed polymer and gels with an autonomous self-oscillating function by utilizing the Belousov-Zhabotinsky (BZ) reaction. Under the coexistence of the substrates, the polymer undergoes spontaneous cyclic soluble-insoluble changes or swelling-deswelling changes (in the case of gel) without any on-off switching of external stimuli. By using microfabrication technique, ciliary motion actuator or self-walking gel have been demonstrated. Further, in order to realize nano-actuator, the linear polymer chain and the submicrometer-sized gel beads were prepared. By grafting the polymers or arraying the gel beads on the surface of substrates, we have attempted to design self-oscillating surface as nano-conveyer. For application to biomaterials, it is necessary to cause the self-oscillation under biological condition without using non-biorelated BZ substrates. So we attempted to introduce pH-control site and oxidant-supplying site into the polymer. By using the polymer, self-oscillation only in the existence of biorelated organic acid was actually achieved.

Abstract: BaTiO3 nano-sized powders were successfully prepared by spray pyrolysis using multiphase plasma under the air atmosphere. The particles characteristics of BaTiO3 nano-sized powders were studied by SEM and XRD. The effect of volume of arc plasma and precursor solution on the formation of BaTiO3 nano-sized powders was investigated. The use of Ba-Ti complex precursor solution derived from lactic acid led to formation of tetragonal BaTiO3 nano-sized powders with 140 nm size. As for BaTiO3 ceramics, the effect of sintering temperature on relative density and the temperature dependence of dielectric properties were investigated.

Abstract: Self-oscillating gel is designed by copolymerizing the catalyst for the Belousov-Zhabotinsky (BZ) reaction with thermosensitive polymer. The cylindrical-shaped specimens of NIPAAm-co-(Ru(bpy)3 gel were prepared by copolymerizing (Ru(bpy)3) monomer as catalyst with NIPAAm as thermosensitive polymer. Swelling behavior during self-oscillating of gel by BZ reaction was observed using CCD camera and the force due to this reaction was evaluated using semiconductor gauge. Self-oscillating swelling-deswelling behavior in samples with different swelling ratio was evaluated by this apparatus, and mechanical parameters such as Young’s modulus, stress amplitude and oscillating period were quantitatively estimated.

Abstract: Self-oscillating gel is designed by copolymerizing the catalyst for the Belousov- Zhabotinsky (BZ) reaction with thermosensitive polymer. The cylindrical-shaped specimens of NIPAAm-co-(Ru(bpy)3 gel were prepared by copolymerizing (Ru(bpy)3) monomer as catalyst with NIPAAm as thermosensitive polymer. Tensile tests were performed with cross-head speed of 10 )m/s in pure water at 20°C. Stress-strain curves were plotted using tensile load measured by semiconductor gauge and strains calculated from observation of the gel. Fracture strain and Young’s modulus were obtained from these curves. Also Poisson’s ratio was estimated from the ratio of strains in longitudinal and radial directions.