MEMS (Micro Electro Mechanical Systems) enables the fabrication of value-added system devices on silicon chips. Micromachining that is an extended integrated circuit technology is used for the fabrication. A rotational gyroscope with an electrostatically levitated ring rotor was developed for inertia sensing. Wafer level packaging enabled MEMS relay for LSI tester. Multi-probe data storage and multicolumn electron beam lithography are realized by array MEMS which take advantages of photolithography and nanostructures such as carbon nanotubes formed in them. Microprobes and microresonators provide high sensitivity and spatial resolution by utilizing nanostructures.
Recent microtechnology has opened various application fields in chemistry. In analytical chemistry, in particular, ‘Micro Total Analysis Systems (μ-TAS)’, has been established as one of the largest research fields. On the other hand, growing interest has also focused on applications in biochemistry and synthetic organic chemistry. In this paper, we introduce some applications for Continuous-Flow Chemical Processing (CFCP), immunoassay, and organic synthesis by using a surface modification as examples of micro chemical processes.
Bonding technologies play important roles in MEMS fabrication processes, especially for reliability and commercial competitiveness. One of those technologies is wafer direct bonding. Conventional wafer direct bonding utilizes hydrogen bonds between hydroxyl groups on wafer surfaces. It has an advantage of pressure-less bonding; however, high temperature annealing step, required to achieve practical bonding strength, limits its application to MEMS devices. In wafer direct bonding, surface state of the wafers largely influences the bonding. Therefore, several surface treatments have been adapted. Surface activated bonding (SAB) utilizes sputter etching of the bonding surface in vacuum. The sputter etched surface is expected to be in an active state and form strong bonds at lower temperatures. Various materials such as silicon, compound semiconductors and metals can be bonded at room temperature. On the other hand, in case of SAB between oxide wafers, low temperature annealing, typically at 200oC, is effective to achieve strong bonding. This means that a simple model of bond formation between clean surfaces is not enough to explain the bonding process of SAB.
Protein motors are chemo-mechanical ATPases that can naturally generate force and move cargo or as individual molecules along tracks of protein polymers (actin filaments or microtubules), using chemical energy from adenosinetriphosphate (ATP) hydrolysis. In order to harness these protein motors to power nanometer-scale devices, we have investigated effective and non-destructive methods for immobilizing them and/or their protein filament tracks on surfaces and to steer the output of these motors, i.e. force and movement, into defined directions. We succeeded in aligning protein motors (myosin and its proteolytic fragments) on microscopic tracks composed of polytetrafluoroethylene (PTFE) deposited on the surfaces or polymethylmethacrylate (PMMA) prepared lithographically. Control of protein-motor driven movement of protein filaments was successfully made by using micrometer-scale grooves or walls lithographically fabricated on glass surfaces, and thus unidirectional movement of the filaments was accomplished by adding simple patterns onto the grooves or walls.
In a liquid crystalline (LC) monolayer on liquid surface, simple rod-like chiral molecules exhibit a unidirectional rotational motion under transmembrane water transport. The coherent collective precession motion was observed in various chiral LC monolayers, the rotational speed of which is linearly increased with the chirality strength and also the transmembrane water transfer rate per unit of time. When either the chirality or water transfer direction is inversed, the rotational direction of the precession is completely reversed. The result indicates that the molecular chirality works as a propeller and its unidirectional rotation is driven by water transfer across the membrane. Each chiral molecule cannot overcome the thermal fluctuation alone, but the LC interaction amplifies the molecular motion and transforms it into a coherent collective precession of entire molecules. This might propose a new approach to nanomachines.
The tunneling current flowing between the tip and H-adsorbed Si(001) surface in Scanning Tunneling Microscopy (STM) is investigated using the first-principles calculations based on the real-space finite-difference method. The resultant current map is consistent with the STM image in which H-adsorbed dimer looks geometrically lower than the bare dimer. Although the isosurface of the local density of states above the H-terminated Si dimer, which are mainly attributed by the Si-H σ bonding states, locate itself higher than that above the bare Si buckled dimer, these bonding states do not contribute to the tunneling current. On the other hand, many electrons tunnel from π bond of the unreacted dimer into the tip. Accordingly, the H-adsorbed dimer appears geometrically lower than the bare dimer in the STM, since the tip must approach closer to the sample surface in order to achieve the constant tunneling current.
Highly concentrated pastes of Au and Ag nanoparticles were prepared by a novel method using a comb-shaped block copolymer and an amine as protective colloid and reducing agent, respectively. The nanoparticles were applied to paint colorants utilizing the surface plasmon light absorption. Au and Ag nanoparticles exhibited clear red and yellow colors, respectively. It was revealed that the nanoparticles possess aesthetic color properties such as transparency and color saturation as well as excellent weather durability. Further, a novel metal paint system was also developed from using the condensed Ag paste, which enables us to produce metal like coatings by a simple, dry and environmentally friendly process.