Toshiaki Mitsui

Development of CNT-Coated Diamond Grains Using Self-Assembly Techniques for Improving Electroplated Diamond Tools

Single crystalline diamond grains covered by nested carbon nanotubes (CNTs) were constructed using self-assembly techniques. The acid-treated CNTs (MWCNTs-COOH) are first adsorbed onto amine-terminated diamond grains, which were chemically functionalized by silane coupling treatments, in N, N-dimethylformamide solution. Then, the drying and readsorption cycle deposited CNT coatings on the diamond grains due to CNT-CNT interactions caused by van der Waals forces. When the diamond grains were bonded to steel substrates by electroplating using nickel sulfamate plating bath, the bonding strength of the CNT-coated diamond grains to the Ni matrix was almost twice as large as that of the normal diamond grains. Hence, the CNT-coated diamond grains are very useful for improving the tool life of electroplated diamond tools.

5-Axis Capacitive Motion Sensor Fabricated by Silicon Micromachining Technique

We have developed a 5-axis capacitive motion sensor by using silicon bulk-micromachining technique. This sensor has a seismic mass which is vibrated along Z-axis by electrostatic force at the resonant frequency of 1875Hz. The Z-axis acceleration (Az) translates a mass parallel and the X-, Y-axis accelerations (Ax,Ay) tilt a mass. Corioris force induced by 2-axis angular rates (Ωx,Ωy) tilt a mass synchronizing with driving frequency. Therefore the 3-axis accelerations and 2-axis angular rates can be detected selectively because of the difference of frequency. Measured sensitivities of accelerations were approximately 20fF/G in Az, and 6fF/G in Ax and Ay. The sensitivities of angular rates are approximately 3aF/[deg/s] in Ωx and Ωy. The chip size of developed sensor is 8.4mm×8.0mm×1.4mm.