Metallic Glass as a Mechanical Material for Microscanners

Microelectromechanical system (MEMS) actuators essentially have movable silicon structures where the mechanical motion can be activated electronically. The microscanner is one of the most successfully commercialized MEMS devices which are widely used for collecting optical information, manipulating light, and displaying images. While silicon is abundant, it is also brittle and stiff and when microprocessed, defects are not uncommon. These defects result in weakness under torsional stress and this has been the key factor limiting the scanning performance of the microscanner. Here a metallic glass (MG)‐based microscanner is reported with MG as the material for the moving torsion bars. The low elastic modulus, high fracture toughness, and high strength of MG offers, for the first time, an ultralarge rotating angle of 146° with power consumption lowered to the microwatt range, and a smaller driving force and better actuation performance, than conventional single crystal silicon and polycrystalline silicon. The high spatial resolution and large scanning field of the MG‐based microscanner are demonstrated in the tomographic imaging of a human finger. This development of an MG‐based MEMS possibly opens a new field of low‐powered MEMS devices with extreme actuation and enhanced sensing.     

用体硅微加工工艺实现的微纳电械系统

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Deep Reactive Ion Etching of Lead Zirconate Titanate Using Sulfur Hexafluoride Gas

A deep reactive ion etching (RIE) technique that uses sulfur hexafluoride (SF₆) gas has been developed for lead zirconate titanate (Pb(Zr,Ti)O₃, PZT) three-dimensional microfabrication from PZT ceramic blocks. The etching was performed by using an inductively coupled plasma that was generated in a narrow-gap vacuum chamber. The etch depth was 70 µm with a maximum etch rate of 0.3 µm/min and a selectivity of PZT to the electroplated nickel mask of >35:1. The sidewalls of the PZT structures were tapered, with base angles of ∼75°. Both positive RIE lag and unexpected ultrafine-slit etching phenomena were observed.     

Trench filling characteristics of low stress TEOS/ozone oxide deposited by PECVD and SACVD

In this paper low stress silicon oxide was deposited with tetraethylorthosilicate (TEOS, Si(OC₂H₅)₄)/ozone by plasma enhanced chemical vapor deposition (PECVD) and sub-atmospheric chemical vapor deposition (SACVD) for deep trench filling. Two kinds of PECVD oxide were fabricated: Coil antenna inductively coupled plasma (ICP) oxide and parallel plates capacitive coupled plasma (CCP) oxide. Adding ozone into the deposition process enhances the trench filling capability. Oxide filling in a deep trench (5 m wide, 52 m deep) was carried out using the SACVD process, which gave excellent conformal step coverage. However, the coil antenna ICP oxide was suitable as a sealing material. The effects of argon ion sputtering and magnetic field in the PECVD for the trench filling are discussed in this paper. Because the low temperature processes of PECVD and SACVD, the thermal residual stress was reduced and a low stress film of 85 MPa compression is available.This work is supported by a Grant-in-Aid (No. 13305010) from Japanese Ministry of Education, Culture, Sports, Science and Technology. A part of this work has been performed in Venture Business Laboratory, Tohoku University.     

Magnetically coupled oscillators applicable to high-sensitivity mass detection

Microsystem Technologies - In this paper, a system of magnetically coupled oscillators consisting of a Π-shaped horizontal cantilever and a rectangular vertical cantilever with a frequency...     

High aspect ratio fabrication method using O2 RIE and electroplating

A polyimide-based process for the fabrication of vertical structures with high aspect ratio has been developed. O₂ reactive ion etching (O₂ RIE) has been employed in the polyimide processing. Achieved etching characteristics of the O₂ RIE system are: 4.0 m/min etching rate, 15 aspect ratio, 75 m etching depth. Polyimide has excellent chemical and thermal properties which makes it a good building material for micromachines. Polyimide could be also used as molds for electroplating. Electroplated copper structures were formed in the polyimide molds and metal gears were fabricated by these fabrication technologies. New possibilities for micromachining were opened by the use of O₂ RIE and electroplating.This work was supported by Japanese ministry of Education Science and Culture under a grant-in-Aid No. 03102001.     

PZT-Polymer 1-3 Composite for High Resolution Ultrasonic Imaging

A novel process has been developed to construct PZT-polymer 1-3 micro composites for high-resolution ultrasonic imaging for medical diagnosis. The key technology is the lost silicon (Si) mold process, by which PZT micro-rod arrays have been successfully fabricated with the finest rod size being 7 μm, the highest aspect ratio exceeding 15. Such fine-scale high-aspect-ratio PZT structures, which are essential for realizing high imaging performance, have never been realized by any conventional technique.     

Design and characteristics of large displacement optical fiber switch

Plastic optical fiber (POF) is suitable for indoor local area network (LAN), for example, in-home or office networks, because of its flexibility and its ease of connection due to its relatively large core diameter. A 1/spl times/2 optical switch for indoor LAN using POF and a shape memory alloy (SMA) coil actuator with magnetic latches was successfully fabricated and tested. In this paper, the design concept and the characteristics of this switch are described. To achieve switching by the movement of a POF, large displacement is necessary because the core diameter is large (e.g., 0.486 mm). A SMA coil actuator is used for large displacement and a magnetic latching system is employed for fixing the position of the shifted POF. For this design, the insertion loss is 0.40 to 0.50 dB and crosstalk is more than -50 dB without index-matching oil. Switching speed is less than 0.5 s at a driving current of 80 mA. A cycling test was performed 1.4 million times at room temperature. Another optical fiber switch was fabricated and successfully actuated using plastic clad fiber (PCF). PCF also has a large core diameter (e.g., 0.20 mm) and optical switches using PCF will be useful for short distance networks between buildings.     

Local electrical modification of a conductivity-switching polyimide film formed by molecular layer deposition

The electrical modification of a conductivity-switching polyimide film via molecular layer deposition (MLD) is studied for ultrahigh density data storage based on a scanning probe microscope (SPM). A PMDA-ODA (PMDA = 1, 2, 3, 5-benzenetetracarboxylic anhydride, ODA = 4, 4-oxydianiline) film as a recording medium is uniformly formed from a self-assembled monolayer on a Au surface by MLD. It is demonstrated that the conductivity of the film can be changed by applying a voltage between a SPM probe and the film. This conductivity-switching phenomenon is discussed by the molecular orbital approach and considered to be caused by the charge transfer effect or carrier trapping effect of PMDA-ODA.     

Influence of one bout of intensive running on lymphocyte micronucleus frequencies in endurance-trained and untrained men

This clinical investigation was designed to determine the effect of changes in loading patterns on left ventricular (LV) relaxation when heart rate was maintained constant. Not only were changes noted in total load or time in which load is changed, but also the contour of the ascending aortic systolic pressure wave. Twenty patients were studied. LV and ascending aortic pressure were measured by a multisensor catheter under baseline conditions (C) and after an intravenous injection of 2.5 microg angiotensin (A) and sublingual administration of 0.3 mg nitroglycerin (N). A bipolar pacing catheter was placed in the right atrium to maintain a constant heart rate throughout the protocol. The augmentation index (AI), which characterizes the contour of the ascending aortic systolic pressure wave, was defined as the ratio of the height of the late systolic shoulder/peak to that of the early systolic shoulder/peak in the pulse. The rate of isovolumic LV pressure decline was calculated as a time constant (Tau). Ascending aortic systolic pressures (mmHg) were 127+/-29 (C), 158+/-20 (A) and 109+/-15 (N). AI were 1.61+/-1.14 (C), 2.08+/-1.11 (A) and 1.27+/-1.14 (N). Tau values (msec) were 49+/-4 (C), 54+/-4 (A) and 45+/-5 (N). Tau was prolonged proportionally with increasing AI (p<0.001, r=0.64). It was concluded that late systolic pressure augmentation in the ascending aorta is one important factor that influences the rate of isovolumic left ventricular pressure decline in humans.