Self-assembly of fine particles on three-dimensional structure enables a lot of applications. Dip-coating is one of the processes to produce such assemblies and often utilized because of high productivity and simplicity, just drawing up from suspension in which particles are dispersed. However, it has been applied only to planar substrates because the spreading profile of suspension is constant when the drawing up speed is constant while that on three-dimensional substrates becomes complex. This study aims to realize uniform assembly on the three-dimensional structure with the texture fabricated using a five-axis milling machine. First, the spreading profile of water on directionally slanted grooves on planar substrate was investigated. It was found that water is well held by pinning and the effect becomes highest when the slant angle 30°. It was also found that the coverage increased when the groove pitch 100μm and the drawing up speed 12.5mm/s. Then, assembly on the three-dimensional profile was tried. Dip-coating process was carried out referring the appropriate conditions for planar substrates. The effectiveness of the texture was verified comparing the assembly results on parabolic surface with/without it. Finally, it was found the uniform assembly on parabolic surface is applicable to optical element.
Nanostructure processing method with high productivity is desired for many practical uses. Recent studies report that femtosecond laser process is expected as one of high productive process. By irradiating femtosecond laser to the polished target surface, it is possible to form a nanostructure on laser irradiation entire area. But this method cannot be easily applied to glass substrate because this method needs to generate surface plasmon polariton by laser irradiation. Our research group invented a new method for forming a nano-sized texturing on a glass by using light absorbable metal nanoparticles and glass precursor. We made nano-sized surface structure on the glass sample, and showed the anti-reflection effect.
Grinding has widely been applied to the peripheral finishing of hard materials like hardened steel, since the milling process often causes the regenerative/mode-coupling chatter vibrations due to high specific cutting force and low stiffness of slender end mills. A new machining method is proposed in which high-efficiency peripheral finishing of hard materials is realized with highly-varied-helix end mills at low-radial immersion. Large axial depth of cut (high surface generation rate) can be attained by the proposed method, because the mode-coupling chatter is avoided by setting the radial immersion to be small and the regenerative chatter is suppressed by using the highly-varied-helix end mills. This paper presents experimental verification of the proposed machining method and comprehensive explanation of its stability increase by utilizing “regenerative-effect cancelation diagram” proposed in this study.
This paper deals with a force estimation method by using driving current of a piezoelectric actuator. Because the size of sensors sometimes restricts the size of a whole device, a sensor-less control is preferable to build a device compactly. A mechanical clamp device including the actuator was represented as an equivalent electric circuit by applying Martin's model, and a force change is calculated from the driving current. Although only dynamic behavior generates the electric charge in the piezoelectric actuator, a static stress varies its piezoelectric constant. Then the stiffness of the piezoelectric actuator will change. The preload of the piezoelectric actuator can be estimated from the resonant frequency of residual vibration of the driving current, which coincided with the mechanical vibration of the device. Consequently, the generated force can be represented as a linear function of the applied voltage and resonance frequency of the current. The force containing the static preload was estimated with an error less than 12% for step response.
We have developed a laser frequency calibration system with an optical frequency comb linked to the national standard of frequency. The frequency standard oscillator for comb stabilization was synchronized to the coordinated universal time of national metrology institute of Japan (UTC(NMIJ)), and the residual error of its frequency was remotely calibrated. Thus, the comb frequency was traceable with respect to the national standard of frequency. Using the developed system, we measured the frequency of a 633nm iodine stabilized He-Ne laser that was previously calibrated by using the secondary standard based on the national primary standard of laser. The results obtained by using the comb were in a good agreement with those obtained by using the secondary standard of laser. To ensure measurement reliability, we measured the relative stability of the developed system with respect to the one developed by NMIJ. A relative frequency stability of 5.2×10-14 was obtained.