Papers by Author: Jun Ichi Hamagami

Abstract: A novel micropatterning process for a particle assembly has been performed by using an electrophoretic deposition (EPD) method with a local electric field in a colloidal suspension generated by a three-electrode system. Monodisperse silica colloidal spheres with a diameter of 300 nm were used to fabricate micropattern of colloidal crystal. An interdigitated gold-microarray electrode with a 10 μm of width and a gold plate electrode were used as the working and the counter electrodes, respectively. After optimization of the EPD processing parameters, a micropattern was constructed from silica colloidal spheres. It had a relatively close-packed structure formed onto the interdigitated microarray electrode. This micropattern showed a characteristic optical reflectance peak due to Bragg’s law.

Abstract: A novel micro-fabrication technique for particle assembly has been performed by an electrophoretic deposition (EPD) method using a local electric field in a colloidal suspension generated by a microelectrode. This unique EPD technique was called a “μ-EPD process”. Monodispersed polystyrene microspheres with diameters of 204, 290, and 320 nm were used in this study. A 50 μm Pt wire embedded into a polytetrafluoroethylene tube and an ITO glass slide were employed as the micro-counter electrode and the substrate, respectively. A slow deposition rate in the μ-EPD process was preferable to form a high quality micro-deposit consisting of a three-dimensional periodic polystyrene array. Under the optimized μ-EPD conditions, three-dimensionally ordered polystyrene particles were deposited in front of the micro-counter electrode. This micro-deposit constructed from polystyrene particles with a close-packed structure showed a characteristic optical absorption peak due to Bragg’s law.

Abstract: Micrometer wire consisting of microbeads was successfully fabricated onto a patterned conductive electrode substrate by an electrophoretic deposition (EPD) process with precise control of electric field distribution generated in the colloidal suspension. Monodisperse polystyrene microspheres with 320 nm in diameter and an interdigitated microarray Au electrode having 10 μm in width and 5 μm in spacing were used in this EPD system. A micropattern of polystyrene particles with two dimensional arrays was formed onto the patterned electrode by the EPD process with two electrode system using an electrostatic interaction between the electrodes and the charged particles in the suspension.

Abstract: A new proton-conducting membrane was prepared consisting of uniformly macroporous silica matrix and a proton-conducting gel polymer, 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS). Three-dimensionally ordered macroporous silica membrane was fabricated by use of a colloidal template method with mono-dispersed polystyrene beads. Surface sulfonation of the pores in the silica matrix was performed by using 1,3-propanesultone. The sulfonated silica matrix exhibited about 400 times higher proton conductivity than unmodified one. The proton conductivity of the composite membrane was also successfully enhanced by using the sulfonated silica matrix.

Abstract: Thin films of lithium ion conductive ceramic Li4+xAlxSi1-xO4 were fabricated on Au substrate using sol-gel process. The sol of Li-Al-Si-O was spread on Au substrate using a spin coater, and it was gelated at room temperature. The gel was calcinated at 400 °C and heat-treated at high temperatures between 500 °C and 800 °C in air. The addition of poly(vinylpyrrolidone) (PVP) was effective in stabilizing the sol. Furthermore, the morphology of the obtained thin film was changed by the PVP additive. Li4+xAlxSi1-xO4 thin film prepared at 800 °C exhibited a Li+ ion conductivity of 10-8 S cm-1 at room temperature.