Coils are used in many electronic devices as inductors in mobile units such as mobile phone, digital cameras, etc. Inductance and quality factor of coils are very important value of the performance. Therefore, the requests for coils are small size, high inductance, low power consumption, etc. However, coils are unsuitable for miniaturization because of its structure. Therefore, we have proposed and developed the microcoils of high aspect ratio with the dipping method and an X-ray lithography technique. In dipping method, centrifugal force and highly viscous photoresist solution were key points to evenly apply resist in the form of thick film on metal bar. The film thickness of resist on bar was achieved about 50 μm after single coating. Using these techniques, we succeeded in creating threaded groove structure with 10 μm lines and spaces on 1 mm brass bar. In this case, the aspect ratio was achieved five. It is very expected the high performance microcoil with high aspect ratio lines could be manufactured in spite of the miniature size.
This paper describes the development of a SCARA-type haptic device, which will be used to assist a human operator in non-contact object handling of silicon wafers using electrostatic levitation. The device has three degrees of freedom, of which only one (vertical) is actively controlled. By utilizing the admittance control paradigm, a high vertical stiffness and a high output force can be achieved. These properties are necessary for the intended application of non-contact object handling to prevent instabilities (induced by the human motion) of the electrostatic levitation system. As the nominal air gap between object and electrostatic levitator is in the order of 350 micrometer, with an allowable position error of about 150 micrometer, instability can easily occur if there is no haptic assistance, especially in the picking up or placing process. The developed SCARA-type haptic device has a mechanical stiffness of 51 N/mm for the vertical direction when it is in the weakest posture, which is sufficient for the non-contact handling task. The design and performance of the haptic device for the active vertical degree of freedom are described in this paper.
The LIGA process consists of lithography which use synchrotron radiation light, electroforming and molding has attracted attention in microstructure fabrication technology. At the molding process of LIGA process, a cast of especially high aspect ratio structure is assumed that it is difficult to pull out from the mold. But, mold releasability is improved by tapering the structure. In this research, The diffraction exposure technique is newly proposed. Diffraction is caused by providing a clearance between the resist and the mask. The structure fabricated is the lines and intermediate space whose processed depth is 200μm and designated the taper angle 5° as set point. The experiment was done by changing gap, dose and slit width. When dose is increased, processed width increased, but taper angle does not change. When gap is increased, both processed width and taper angle increased. When slit width is expanded, processed width increased, but taper angle decreased. The taper angle of 3.7 degrees was achieved under the conditions for slit width of 7μm, gap of 150mm and 15000 (mA·sec/mm).
Reliable joining technologies are essential for fabrication of microstructures such as micro-machines, and particularly technologies that are capable of jointing different types of materials. However, these technologies cannot be used for materials that have different rates of thermal expansion or in cases where the adhesives have an effect on the properties of the component materials. Our research focused on developing a direct jointing technology which employs hydrogen bonding. In this technology, OH radicals are absorbed into the surface of the material to be bonded by modifying its surface properties by ion irradiation. We studied the modification of the surface properties of two resins, (SU-8 and PMMA) by H2O ion irradiation and Ar cleaning. It was confirmed that the presence of H2O ions on the surface of these resins improved their hydrophilic properties and also the peel strengths of Cu membrane s deposited onto both resins. Based on the results of these studies, a series of experiments were conducted in which two different materials, (copper plus one or other of the resins) were joined directly and the results were evaluated. Each of the resins could be joined to copper by heating to a temperature of 100°C and pressurizing to 10 MPa. This jointing technology will now be applied to the fabrication of the tilt sensors that we are currently developing.
Recently, increased user demand for quiet vehicle environments has resulted in the need to develop low-noise gears that do not generate noises that are harsh on to the human aural. The principal method for reducing meshing transmission error has been to gear design with as many teeth as possible. However, while these design methods have focused on decreasing gear noise, they have not considered the relationship between gear noise and the background noise of vehicle interiors. In fact, it would appear that no research considering the human aural characteristics associated with gear noise under these conditions has been conducted to date. Furthermore, the problem of gear noise on background noise in vehicle has increased as the use of hybrid engine technology in vehicle has become more pervasive in recent years. The proposed technique for reducing gear noise involves gear design that frequency control of gear noise by changing the number of teeth. The technique described here considers human aural limit and the influence of masking, and how these are affected by the tooth settings of low noise gear. This was achieved by assessing human aural characteristics in the unique acoustic environment of the vehicle interior. Then, the relationship between the number of teeth and the sound pressure level of gear noises was investigated. It was found that the proposed method of varying the number of teeth was effective for designing gears with optimal human aural characteristics.
To develop case-carburized gears with high loading capacity, the surface durability of a developed Cr-Mo-Si steel (with 1 mass% Si added in the chemical composition) was studied. Initially, the fatigue tests of case-carburized Cr-Mo-Si steel and Cr-Mo steel melted in a hypoxia vacuum were carried out using a two-roller contact fatigue tester. Next, the changes in the surface failure, surface roughness and sectional hardness distribution of the test rollers were examined using a scanning electron microscope, a surface roughness measuring instrument and a penetrometer, respectively. In the case of Cr-Mo-Si steel test rollers under rolling-sliding contact, the following results are obtained in comparison with Cr-Mo steel test rollers: micro pitting area ratio is lower under a medium load, the pits do not occur under a heavy load, and the value of surface variation is lower. Therefore, it is clear that the developed Cr-Mo-Si steel can be applied to case-carburized gear materials under a heavy load.
A pneumatic system has several advantages, which are cheapness, lightweight, and reliability to human and environment. These advantages are adapted to some research areas, such as industrial lines, medical and nursing cares, and rehabilitation tools. However, the pneumatic system needs several devices; compressor, air tube, and control valve. This research aim to downsize pneumatic system. In this paper, a new method of multiplex pneumatic transmission for multi-pneumatic servo system is proposed. The valve for this system consists of two vibrators supported by springs, which was designed with simple and cheap structure. The working principle of the valve is vibrators resonance from multiplex pneumatic transmission and it is possible to work as ON/OFF valves without electric wire. Dynamic simulation was used to confirm the working principle of the resonance driving system. A prototype device confirming the principle was designed and developed based on the simulation. The experiments show that this new control system works very well to control two separated valves through single pneumatic tube.
The contact stress in a gerotor pump is addressed in this paper because the gerotor pump cannot be adjusted for wear. The first part of this paper presents a simple and exact rotor profile equations of the gerotor pump. In the second part of this paper, an explicit formula to avoid undercut in the inner-rotor of the gerotor pump is proposed by examining the minimum radius of curvature of the inner-rotor tooth profile on the convex section. It is found that undercut does not occur so long as the minimum value of the radius of curvature on the convex section is not less than zero. Next, the contact stresses without hydrodynamic effect between the inner and outer-rotors are evaluated through the calculation of the Hertzian contact stress in the rotor teeth. Based on the above results, we finally present the wear characteristics of pHVs factor, which is proportional to the wear rate, between the rotors of the gerotor pump under quasi-static and dry contact conditions.
With the recent progress in downsizing and the sophistication of various industrial products, the need for more compact actuators is increasing. Actuators account for the larger percentage of volume and weight of a product compared with other parts and devices. We have proposed fabrication process of spiral micro coils that employs X-ray lithography. This process will be effective for fabricating coils of a high aspect ratio lines. Reducing the size of coil lines and increasing their aspect ratio are expected to reduce the size and increase the output of actuators. Using this process, we formed spiral coil lines that can be used in electromagnetic actuators. X-ray lithography was used to form a high aspect ratio helical structure on the surface of an acrylic resin pipe. As a measure to suppress void generation, which is one of the shortcomings of electroplating processes, the sputtering apparatus and plating equipment were improved, a pretreatment process was additionally provided, and the actual electroplating method was improved. As a result, a void-free metallic deposit could be formed on a thin coil line. At the final step of this research study, we etched the coil line to determine optimal etching conditions.
The X-ray lithography of uses synchrotron radiation is one of the microprocessing structure fabrication technology. In X-ray lithography, precision of the fabricated structure is influenced by precision of the X-ray mask considerably. Conventionally, the X-ray mask was fabricated with UV lithography. However, it is difficult to fabricate the highly precise X-ray mask because of the tapering X-ray absorber. We introduces the ability of Si dry etching technology into UV lithography in order to fabricate untapered, high precision X-ray masks containing rectangular patterns. This new X-ray mask fabrication method uses a high-precision microstructure pattern formed by Si dry etching, thereby fabricating high aspect ratio, narrow line width resist microstructures that cannot be achieved by any conventional technology. An Au for the X-ray absorber is made to the groove of the structure, and it is formed by electroplating. The silicon substrate itself is used as seed layer and the structure is fabricated with the photo resist whose resistance is higher than silicon. It can be expected the gilding growth from only the bottom layer. High-density Au functions sufficiently as an absorber. Au plating was formed only from the base of the structure ditch and could bury Au of thickness 3.5μm in a narrow place of 2.7μm in width well. The fabricated structure using X-ray lithography. Highly-precise rectangular structure could be fabricated.
Since surface forces prevent micro-machines from moving in the air, there are a lot of difficult problems to be solved concerning the reliability of micro-machines. Surface forces depend strongly on dust and contaminants. Therefore, we should be considering the attachment and detachment of micro-applications between interactive contact surfaces related to the locomotion of micro-machines. We observed that dusts have effects upon contact surface forces via the locomotion of cantilever in the air. First, we made a stainless steel cantilever with a glass sphere (dry borosilicate glass sphere, curvature radius: R=10μm) glued on top. In addition, we created an asperity array at the micro-sphere's surfaces on the stainless steel cantilever using an FIB (Focused Ion Beam). The experiment was performed using an AFM (Atomic Force Microscope). From the results, we found out that contact surface forces are influenced remarkably by dust debris in the air. The spheres with asperity arrays tend to hinder the accumulation of dust than the spheres without asperity arrays in abrading work using the same normal spring constant (=kn) of the cantilever. Moreover, among the cases with non-asperity arrays, the accumulation of dust on the sphere's surface is lower in the thin cantilever than the wide cantilever. To prevent contact surface forces from increasing by the accumulation of contaminants, micro-machines must have locomotion and asperity arrays on any surface that comes in contact with severe natural conditions.
We present a process for the fabrication and assembly of a novel spiral-shaped micromirror manipulator for free space optical switching. The manipulator is comprised of two different parts, which are fabricated using conventional surface micromachining processes. The footprint of the assembled device is about 600μm and the height of the micro pyramid is 200μm. In spite of conventional approaches to microsystem design, which prefer devices with monolithic and self-assembling properties, the two parts are fabricated on two different chips. They are then assembled using a spatial mechanical approach. A number of separate spiral and pyramid parts are fabricated and the first assembling test on a single actuator is performed. In this paper, the Surface micromachining processes used for fabrication of the parts are presented and their sensitivity and issues are discussed. Spatial mechanical assembly results are presented and process issues are addressed.
This paper describes a new traction drive transmission which features a self-loading mechanism to achieve high efficiency and a simple ratio-change system without synchronizers. A cam incorporated in the roller support provides loading force in proportion to the force being transmitted, and the speed ratio is selected by changing the distance between the shafts. Tests conducted to evaluate the loading force, transmission efficiency and ratio changes have confirmed that this transmission achieves high efficiency equal to that of gears and quick ratio changes without any shift shock. This mechanism is expected to be a next-generation transmission for automobiles, achieving low cost, small size and high levels of performance. The study results show its fundamental performance and promising future.