Fabrication of laser induced periodic surface structure for geometrical engineering

The paper presents the highly ordered geometrical structures of laser induced periodic surface structure (LIPSS) in azobenzene urethane polymer (DR19 polymer) from 4-(N,N-dihydroxyethylamino)-4′-nitroazobenzene (Disperse red 19) with tolylene-2,4-diisocyanate (TDI). One or two regulated striped LIPSS was formed in confined spaces between surface relief gratings (SRG) induced by the s-polarized interfered beams. The pitch of LIPSS was one-half or one-third of SRG pitch. Standing wave with some selected mode between SRG in the surface waveguide is responsible for the formation of the regulated striped LIPSS. The crossed illumination of the interfered beams showed the waffle-like structure for s-polarization beam and the egg crate-like (ECL) structure for p-polarized beam. Photoinduced microscopic molecular ordering was also investigated. The linear polarized beam gave the large optical anisotropy in the polymer and the circularly polarized beam produced the chiral structure. The circular dichroism spectra showed the sharp peak due to the circular Bragg reflection from which the chiral pitch was evaluated.     

International mobility of researchers in robotics,computer vision and electron devices: A quantitative and comparative analysis

We investigated author information in scientific articles by approximately 7,000 researchers for a quantitative analysis of researchers’ international mobility. From top journals, we traced the movements of more than 2,200 researchers in the research domains of robotics, computer vision and electron devices. We categorized countries’ characteristics for the balance between the inflow and the outflow of researchers moving internationally. Flow patterns of international mobility confirm that the United States, China and India exhibit the greatest global flows of researchers, with Singapore and Hong Kong attracting remarkable numbers of researchers from other countries. International mobility focusing on institutions reveals that universities in Singapore receive as many foreign researchers as do research universities in the United States. Furthermore, firms and international collaborative research institutes act as alternative receivers to the universities in the electron devices research domain.     

Fabrication of optics by use of plasma chemical vaporization machining with a pipe electrode

We figure optical surfaces by plasma chemical vaporization machining (CVM) with a pipe electrode, in which an rf plasma generated at the electrode tip under approximately atmospheric pressure moves over the surfaces. We propose a shaping method in which the movement of plasma on the surfaces can be determined. Flat and aspheric surfaces are successfully figured with the desired peak-to-valley shape accuracy of 0.1 microm. The root-mean-square roughness of the resultant surfaces is at the subnanometer level. These results confirm that the plasma CVM and the shaping method have the capability to fabricate optics with high accuracy.     

Rapid erasing of wettability patterns based on TiO2-PDMS composite films

TiO₂-polydimethylsiloxane (TiO₂-PDMS) composite films are prepared using the sol–gel method from a Ti(OBu)₄–benzoylacetone solution containing PDMS. The prepared films are cured by irradiation with ultraviolet (UV) light. Structural changes in the films after UV irradiation are confirmed by UV–vis absorption experiments, which show that an absorption band characteristic of the benzoylacetonate chelate rings disappears. This finding is ascribed to structural changes associated with the dissociation of the chelate rings. The IR spectra of the thin films exhibit a broad absorption band after UV irradiation, indicating that a Ti–O–Ti network forms in the thin film. Contact angles are measured for the TiO₂-PDMS thin films, showing wettability conversion from hydrophobic to superhydrophilic states by irradiation with oxygen plasma for 1 s. This phenomenon is explained by XPS experiments which reveal that the number of carbon atoms decreases, whereas the number of oxygen atoms increases on the surface of the TiO₂-PDMS composite films. Finally, hydrophobic–superhydrophilic patterns are fabricated based on a patterned TiO₂-PDMS composite film. The film displays a rapid change to superhydrophilicity over the whole film surface upon plasma irradiation for 1 s, which means that the wettability patterns are rapidly erasable.     

Fabrication of discrete polystyrene nanoparticle arrays with controllable their structural parameters

We have demonstrated the fabrication of two-dimensionally periodic non-close packed arrays of spherical polystyrene nanoparticles with controllable their structural parameters including diameter and interpartcile distance. The principle of this procedure relies on stepwise integration of spin-coat-assisted colloidal self-assembly of the single layer of close-packed polystyrene nanoparticle on a substrate, and subsequent etching of the particle under atmospheric pressure helium plasma. The plasma process converted the close-packed nanoparticle array into non-close-packed arrangement remaining with unchanged their original spherical shape and periodicity. Owing to the etching process underwent isotropically, the structural parameters could be controlled with nanometric accuracy by the treatment time. The etching rate strongly depended on the working pressure conditions, and the etching rate under 250 Torr was ca. 3 times faster than that of the 760 Torr. The effects of the working pressure indicated the neutral helium radicals and photons diffused from the plasma might be primarily responsible for the etching.     

Finishing of AT-cut quartz crystal wafer with nanometric thickness uniformity by pulse-modulated atmospheric pressure plasma etching

Quartz resonator is a very important device to generate a clock frequency for information and telecommunication system. Improvement of the productivity of the quartz resonator is always required because a huge amount of the resonator is demanded for installing to various electronic devices. Resonance frequency of the quartz resonator is decided by the thickness of the quartz crystal wafer. Therefore, it is necessary to uniform the thickness distribution of the wafer with nanometric level. We have proposed the improvement technique of the thickness distribution of the quartz crystal wafer by numerically controlled correction using atmospheric pressure plasma which is non-contact and chemical removal technique. Heating effects of the quartz wafer in the removal rate and the correction accuracy were investigated. The heating of the substrate and compensate of the scanning speed of the worktable according to the variation of the surface temperature enabled an increase of 50% in the etching rate and 10-nanometric-level accuracy in the correction of the thickness distribution of the quartz wafer, respectively.     

Amorphous nanosilicas induce consumptive coagulopathy after systemic exposure

We previously reported that well-dispersed amorphous nanosilicas with particle size 70 nm (nSP70) penetrate skin and produce systemic exposure after topical application. These findings underscore the need to examine biological effects after systemic exposure to nanosilicas. The present study was designed to examine the biological effects. BALB/c mice were intravenously injected with amorphous nanosilicas of sizes 70, 100, 300, 1000 nm and then assessed for survival, blood biochemistry, and coagulation. As a result, injection of nSP70 caused fatal toxicity, liver damage, and platelet depletion, suggesting that nSP70 caused consumptive coagulopathy. Additionally, nSP70 exerts procoagulant activity in vitro associated with an increase in specific surface area, which increases as diameter reduces. In contrast, nSP70-mediated procoagulant activity was absent in factor XII-deficient plasma. Collectively, we revealed that interaction between nSP70 and intrinsic coagulation factors such as factor XII, were deeply related to nSP70-induced harmful effects. In other words, it is suggested that if interaction between nSP70 and coagulation factors can be suppressed, nSP70-induced harmful effects may be avoided. These results would provide useful information for ensuring the safety of nanomaterials (NMs) and open new frontiers in biological fields by the use of NMs.     

Finite-difference time-domain analysis of time-resolved reflectance from an adult head model composed of multilayered slabs with a nonscattering layer

Finite-difference time-domain (FDTD) analysis has been used to predict the time-resolved reflectance from multilayered slabs with a nonscattering layer. Light propagation across the nonscattering layer was calculated based on the light intensity characteristics along a ray in free space. Additional equivalent source functions due to light from scattering regions across the nonscattering region were introduced into the diffusion equation and an additional set of the diffusion equation was solved by FDTD analysis by employing new boundary conditions. The formulation was used to calculate time-resolved reflectances of three- and four-layered slabs containing a nonscattering layer. The received light intensity and the mean time of flight estimated from the time-resolved reflectance are in reasonable agreement with previously reported experimental data and Monte Carlo simulations.     

Hot explosive compaction of diamond powder using cylindrical geometry

Diamond powders were attempted to be consolidated at elevated temperature using an explosive compaction technique employing a cylindrical configuration. A compacted diamond sample recovered from the center of a cylinder, close to the end plug made of stainless steel showed high hardness and tight interparticle bonding between the diamond powders. The sample was characterized on the basis of X-ray diffraction patterns. No graphitization was observed due to heating or compaction, and the hot compacted sample was highly strained by intensive deformation at elevated temperature.