Maho Hosogi

Silicon Nanotweezers with Adjustable and Controllable Gap for the Manipulation and Characterization of DNA Molecules

We describe electrostatically actuated silicon nanotweezers which are intended for the manipulation and characterization of DNA molecules. The fabrication process combines KOH etching and deep reactive ion etching (DRIE) on silicon-on-insulator (SOI) wafer to form sharp nanotips and high aspect ratio microstructures, respectively. The microelectromechanical system (MEMS) consists of a pair of opposing tips, the distance of which can be accurately adjusted thanks to a high resolution differential capacitive sensor. The device shows a resolution of 5 nm for a displacement range of 3 mum (static mode). It has a resonant frequency at 2 kHz and a quality factor of 40 in air, and 550 in vacuum

Self-hold and precisely controllable optical cross-connect switches using ultrasonic micro motors

In this paper, we propose new optical cross-connect switches using ultrasonic micro motors, whose features are self-hold, precise control, and low electric power consumption. Two methods are examined for optical beam deflection. One method is moving the lens and the other is rotating the mirror by using ultrasonic micro motors. The light from the optical fiber is collimated using a self-focusing (SELFOC) lens and is deflected by moving the lens, with an ultrasonic linear motor, perpendicularly to the fiber axis. The light is then coupled to another fiber. Another proposed method is to use reflection mirrors. This structure is composed of a magnetized material attached to a micro mirror and a permanent magnet mounted on a shaft of an ultrasonic rotation motor. The reflected beam is deflected by rotating the mirror. In both methods, precise beam deflection is demonstrated, and optical switching characteristics are confirmed.

Electrical Conductivity of Lambda DNA–Pd Wire

We investigated the electric conduction of lambda DNA molecules covered with Pd colloids using micromachined DNA tweezers that has a pair of opposing probes for retrieving DNA molecules. The molecules were retrieved from a solution containing lambda DNA by applying RF power between the probes in the solution. The retrieved molecules were then soaked in a colloidal solution containing cationic Pd particles, which results in a DNA–Pd wire bridged between the tweezer probes. Current–voltage curves for the DNA–Pd wire can be measured between the DNA tweezers probes, and the resistivity of the DNA–Pd wire was approximately 74 Ω cm.

Electrical and Mechanical Characteristics of DNA Bundles Revealed by Silicon Nanotweezers

This paper deals with the first simultaneous electrical and mechanical characterization of DNA bundles by a MEMS tool. The silicon-based device has an integrated actuator and a differential capacitive position sensor. Our experiments show that under constant humidity conditions, a rope of DNA has a nearly Ohmic conductivity and behaves as a viscoelastic material.

Vertical Comb-Drive MEMS Mirror for Optical Spectrum Sensing

We have proposed a vertical comb-drive MEMS mirror which can be applied for a spectrometer with phase-shifting method, and fabricated the mirror device using micro fabrication technology. The configuration of the MEMS mirror was designed with three vertical electrostatic comb-drive actuators and hinges at the periphery of the mirror. In the proposed spectrometer, the phase of the light which is reflected at the movable mirror is changed, and obtain the interferogram is obtained by the movable mirror which is driven precisely. We evaluated the moving characteristics of the fabricated MEMS mirror and confirmed that the MEMS mirror could be driven vertically to about 30 mum and also could be tilted. Using this MEMS mirror, we configured the spectrometer with a source of monochromatic light (lambda = 405 nm), and evaluated the spectroscopic characteristic in principle. Therefore, we have confirmed that the fabricated MEMS mirror can be applied to the spectrometer with phase-shifting method.

Multiprobe SPM System Using Optical Interference Patterns

This paper proposes a new composition of the multiprobe scanning probe microscopy (SPM) system using optical interference patterns for a parallel nanoimaging in a large-area measurement. We achieved large-scale integration with 50 000 probes fabricated with microelectromechanical systems (MEMS) technology and measured the optical interference patterns with charge-coupled device (CCD), which was difficult in a conventional single scanning probe. In this research, the multiprobes are made of SiN by MEMS process, and the multiprobes are joined with the Pyrex glass by anodic bonding. We designed, fabricated, and evaluated the characteristics of the multiprobe. In addition, we changed the probe shape to decrease the warpage of the SiN probe. We used the supercritical drying to avoid stiction of the SiN probe with the Pyrex glass surface and fabricated the SiN probe without stiction. We took some interference patterns by CCD and measured the position of them. We calculated the probe height using the interference displacement and compared the result with the theoretical deflection curve. As a result, these interference patterns matched the theoretical deflection curve. We found that this multiprobe chip using interference patterns is effective in measurement for a parallel nanoimaging. We also composed the multiprobe SPM system and evaluated the fundamental characteristics

Free-Space Optical Switch Modules Using Risley Optical Beam Deflectors

This paper describes new optical switch modules based on Risley optical beam deflectors. The Risley deflector consists of two wedge-shaped prisms and precisely controllable rotation mechanisms. An optical beam can be deflected to the direction of two axes by rotating each prism independently. The deflectors potentially have a self-latching function, which provides a reliable switching operation, and a large-deflection angle of 19.2°, which makes the switch compact. We experimentally confirmed that prototype switch modules, hardware volume: 15×15×31 mm3, deflection angle: <19.2°, have a scalability of the switch up to 256 ports, low-loss characteristics of 1.0–1.5 dB, and switching time of within 6 s.

Silicon nanotweezers: A new biophysical tool for molecular experimentation

We describe a MEMS-based method for the biomechanical characterization of filamentary molecules. The system consists of a pair of electrostatically actuated silicon nanotweezers and a differential capacitive sensor that is connected to the moving tip of the tweezers. With such a tool, we achieved sub-nanometer displacement resolution (around 0.2 nm), detected the trapping of DNA nanowires and measured the evolution of their biomechanical characteristics through the shift of the resonant frequency.

Rotary Comb Drive Actuator with an Optical Fiber Encoder

We propose the rotary type electrostatic comb drive actuator with a sensor scale for an optical fiber encoder. This actuator can be expected to measure the amount of the movement of the actuator precisely by using the optical fiber encoder

Multi-Probe SPM using Fringe Patterns for a Parallel Nano Imaging

This paper proposes a multi-probe SPM using fringe patterns which is able to measure the large area. The composition of the chip accumulates 50,000 probes in the area of 5 mmtimes5 mm. We fabricated the multi probes, and by using the chip the fringe patterns image could be taken with the CCD camera