We fabricated a micropump with a circular actuator of shape memory alloy (SMA) diaphragm. The actuator consisted of a TiNi diaphragm of 5mm in diameter and 6μm in thickness, and a glass cap. This was fabricated through a process sequence of Si isotropic etching, flash evaporation of the TiNi thin film, annealing for shape memorization, removing of the undesired Si layer by reactive ion etching, and anodic bonding of the glass cap to the diaphragm structure. The fabricated actuator gave about 90μm displacement at the center of the diaphragm under a bias pressure of 200kPa. The SMA micropump, which was completed by gluing the Si check valve with a cantilever valve flap to the actuator, gave a pumping rate of 3-15μL/min at heating energy of 3-9 J under a bias pressure of 200kPa and at zero back pressure. Experimental data indicate that the fabricated SMA diaphragm is acceptable as an actuator of a micropump, while the fabricated valve structure is insufficient as a check valve for high pressure application due to a leak problem.
Enhancement of hydrophobicity by a roughness mixture was investigated on two different model structures. A two-dimensional particle array and commercial embossed film were employed as a bottom rough surface, and a colloidal silica-fluoropolymer composite was coated on these surfaces. Both model surfaces became superhydrophobic by the roughness mixture. These results were quantitatively analyzed based on their surface morphology. The hydrophobicity enhancement was explained by an effective increase of the solid-air interface area.
Control of spatially localized chemical reactions such as site-selective reversible chemical conversion of functional groups and metal deposition on nano and/or micro areas is important to fabricate new devices in the next generation. In this study, the reaction controls were attempted with a nano probe. In the reversible chemical conversion, amino-terminated self-assembled monolayers (SAMs), which were prepared on Si substrates from (p-aminophenyl)trimethoxysilane (APhS) through chemical vapor deposition, were electrochemically converted into nitoroso-terminate ones using an atomic force microscope. The electrochemical reaction required the positive bias voltages of +0.5 to +3V. In order to define the chemical conversion, the sample substrates were immersed in a solution of pH=4 containing carboxylate-modified polystyrene (PS) spheres. The PS spheres were site-selectively adsorbed on the non-scanned regions. This indicates that non-scanned regions justifiably correspond to amino-terminated SAMs. On the other hand, the PS spheres were not adsorbed on the scanned regions at all, since the regions were oxidized and converted into nitoroso-terminated SAMs. Furthermore, the oxidized regions could also be reduced by a probe with negative bias voltage of −2V. The site-selective electroless deposition was actualized using a surface-induced reduction of gold ions combined with scanning probe lithography. Gold nano- or micro-structures on hydrogen-terminated Si surfaces were demonstrated. After fabrication of an Au nanostructure, 1-hexadecanethiol was immobilized on the Au surface. The result shows that we successfully controlled chemical reactions in nanometer-scale by the formation of metal patterns with the SPM.
Small particles of Ti and Si were produced using a high-voltage discharge technique in aqueous solution. A Ti or Si electrode was cathodically polarized at a cell voltage higher than 180V in an electrolyte solution to trigger spark discharge between the electrode surface and the electrolyte solution. The spark discharge generated intense heat at the spark point and emitted melted materials into the solution. This process produced small particles of electrode materials in the solution. The particle size was in the range of ten nm to sub-μm for Ti and to 10μm for Si. XRD spectra indicated that the surfaces of the Ti particles were covered with oxide that had formed due to high-temperature oxidation in the aqueous solution. For the Si particles, XRD spectra showed only peaks attributed to Si crystals.
Manganese and iridium oxides composite films were obtained by anodic codeposition using a mixture solution of manganese (ll) sulfate and iridium (lll) sulfate, and their electrochromic properties were investigated. To prepare the electrolyte, 0.2wt% manganese (ll) sulfate aqueous solution and 0.2wt% Iridium (lll) sulfate solution were mixed in various proportions. The anodic codeposition was carried out using a pulse wave of 1350mV and −200mV (vs Ag/AgCl), with hold time for 6 sec at room temperature. From XPS analysis, it was confirmed that the manganese-iridium oxide composite films of different oxide ratios can be obtained by anodic codeposition. The electrochemical and electrochromic properties of composite films of different metal oxide ratios have been characterized by cyclic voltammogram in 0.05 M NaOH aqueous solution. The composite Mn-Ir (9 : 1) oxide film shows higher charge densities and a broad and stable C. V. curve compared to that of pure manganese oxide film. The composite Mn-Ir (9 : 1) oxide film exhibited maximum optical density (ΔOD) at 400nm. The morphology of the composite film anodically deposited from MnSO4 : Ir2(SO4)3=9 : 1 electrolyte consisted of nanoparticles of 20-30nm in diameter, while the pure manganese oxide film was fiber, and the pure iridium oxide film consisted of particles of 100-200nm. It seems that enhancement of electrochromic characteristics are due to the nanostructure of the Mn-Ir (9 : 1) composite thin film.
Silicon nitride ceramics with different microstructures were N+ ion-implanted at energies ranging from 50 to 400keV. Wear tests of these ion-implanted materials were carried out using a Block-on-Ring wear tester under non-lubricated conditions. Specific wear rates varied according to ion energy and these results were explained by the fact that the amorphized region varied dependent on ion energy.