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We recently developed a microfabrication technique [microfabrication using laser-induced bubble (microFLIB)] and applied it to polydimethylsiloxane (PDMS), a thermoset polymer. The technique enabled the rapid fabrication of a microchannel on a PDMS substrate and selective metallization of the channel via subsequent plating; however, the technique was limited to surface microfabrication. Therefore, we explored the feasibility of three-dimensional (3D) microFLIB of PDMS using a nanosecond laser. In the experiment, a laser beam was focused inside pre-curing liquid PDMS and was scanned both perpendicular and parallel to the laser-beam axis to generate a 3D line of laser-induced bubbles. In the microFLIB processing, the shape of the created bubbles was retained in the pre-curing PDMS for more than 24 h; thus, the line of bubbles generated by the perpendicular laser scanning successfully produced a 3D hollow transverse microchannel inside the PDMS substrate after subsequent thermal curing. In addition, a through-hole with an aspect ratio greater than ∼200 was easily fabricated in the PDMS substrate by parallel laser scanning. The fabrication of a 3D microfluidic device comprising two open reservoirs in a PDMS substrate was also demonstrated for biochip applications.

The study of the sinking phenomenon of diatom cells, which have a slightly larger specific gravity (~1.3) compared to that of water, is an important research topic for understanding photosynthetic efficiency. In this study, we successfully demonstrated the observation of the sinking behaviors of four different species of diatom using a homemade “tumbled” optical microscope. A homemade 1 mm3 microchamber was employed to decrease the effects of convection currents. In the microchamber, diatom cells were basically settled in a linear manner without floating, although some of the cells were rotated during their sinking. Sinking speeds of the four species of diatom cells, Nitzschia sp., Pheodactylum tricornutum, Navicula sp., and Odontella aurita, were 0.81 ± 5.56, 3.03 ± 10.17, 3.29 ± 7.39, and 11.22 ± 21.42 μm/s, respectively, based on the automatic tracking analysis of the centroids of each cell. Manual analysis of a vector between two longitudinal ends of the cells (two-point analysis) was effective for quantitatively characterizing the rotation phenomenon; therefore, angles and angular velocities of rotating cells were well determined as a function of time. The effects of the cell shapes on sinking velocity could be explained by simulation analysis using the modified Stokes’ law proposed by Miklasz et al.

We propose a method for predicting the concentration of a functional ingredient, procyanidin, in apple using Raman spectroscopy in combination with multivariate calibration analysis. A regression model was constructed by partial least-squares (PLS) regression using the collected Raman spectra and the procyanidin concentrations measured by high-performance liquid chromatography (HPLC). Four different preprocessing algorithms—baseline correction, noise removal, averaging, and multiplicative scatter correction—were applied to the acquired Raman spectra. HPLC was used to determine the procyanidin concentrations in the edible part of apple specimens. The PLS regression model predicted the procyanidin concentration in apple with a coefficient of determination of 0.74, a root-mean-square error of calibration of 7.09 µg/g, and a root-mean-square error of prediction of 14.89 µg/g. In addition, the spectra of the carotenoid pigments were observed from the factors extracted from the PLS analysis. Consequently, we found that the procyanidin concentration in apple can be predicted using Raman spectroscopy measurements of carotenoid pigments of apple peel. Compared with conventional destructive measurements, Raman spectroscopy with the aid of multivariate analysis shows strong potential for the rapid and nondestructive quantitative analysis of procyanidin in apples.

Surface microfabrication of a UV-transparent fluoropolymer (CYTOP) was achieved using direct laser ablation with a femtosecond (fs) oscillator. The commercially available CYTOP is highly transparent and has a low refractive index comparable to that of water. Therefore, this polymer is a candidate biochip material for application in the field of tissue engineering. We have previously developed techniques for microfabrication of CYTOP using nanosecond and amplified fs laser ablation, both followed by wet etching and annealing. However, these techniques were not suitable for some industrial applications due to the generation of debris and cracks around the ablated areas, which called for prolonged etching during the fabrication process. To overcome these problems, we have attempted to directly ablate the surface of a CYTOP substrate using a high-repetition fs oscillator and compared the results with fabrication using an amplified fs laser at a low repetition rate. Consequently, ablation with the fs oscillator resulted in high-quality surface microfabrication of the CYTOP substrate. The fundamental characteristics of CYTOP microfabrication using the fs oscillator were investigated. We also demonstrate the fabrication of a transmission diffraction grating on CYTOP using the fs oscillator, and measure the diffraction efficiency of the grating using a 632 nm He–Ne laser.

Bubbles can be formed by focusing a high-power laser in a liquid. Based on this phenomenon, the present study demonstrated a novel technique, referred to as microFabrication using Laser-Induced Bubbles (microFLIB), for the microfabrication of the thermoset polymer polydimethylsiloxane (PDMS). A conventional nanosecond green laser was focused at the interface between uncured PDMS and a metal target and scanned to generate a line of bubbles at the boundary. The hemispherical shapes of these bubbles produced a groove on the rear side of the PDMS substrate following subsequent thermal curing. After the fabrication of such specimens, metal films could be selectively deposited along the grooves by electroless plating. This process allows rapid, high-quality microfluidic fabrication with potential applications to biochips.

A renormalized perturbation method is developed for quantum maps of periodically kicked rotor models to study the tunneling effect in the nearly integrable regime. Integrable Hamiltonians closely approximating the nonintegrable quantum map are systematically generated by the Baker-Hausdorff-Campbell (BHC) expansion for symmetrized quantum maps. The procedure results in an effective integrable renormalization, and the unrenormalized residual part is treated as the perturbation. If a sufficiently high-order BHC expansion is used as the base of perturbation theory, the lowest order perturbation well reproduces tunneling characteristics of the quasibound eigenstates, including the transition from the instanton tunneling to a noninstanton one. This approach enables a comprehensive understanding of the purely quantum mechanisms of tunneling in the nearly integrable regime. In particular, the staircase structure of tunneling probability dependence on quantum number can be clearly explained as the successive transition among multiquanta excitation processes. The transition matrix elements of the residual interaction have resonantly enhanced invariant components that are not removed by the renormalization. Eigenmodes coupled via these invariant components form noninstanton (NI) tunneling channels of two types contributing to the two regions of each step of the staircase structure: one type of channel is inside the separatrix, and the other goes across the separatrix. The amplitude of NI tunneling across the separatrix is insensitive to the Planck constant but shows an essentially singular dependence upon the nonintegrablity parameter. Its relation to the Melnikov integral, which characterizes the scale of classical chaos emerging close to the saddle on the potential top, is discussed.

Surface plasmon polaritons (SPPs) enable the light to confine to sub-wavelength space. Metallic nanostructure is often used for plasmonic device since plasmon resonance band is generally formed at visible regime. SPPs lead to several orders enhancement of incident light intensity at the metallic nanosurface. While this remarkable effect has been studied for useful application (e.g. SERS, TERS photoluminescence, etc.), it was found plasmon generated highly energetic carriers through Landau damping, referred as hot electrons and holes. The hot carrier induces chemical transformation of molecules at the plasmonic nanosurface. The fact chemically inert molecules reacted by hot carrier has been reported in the recent [1].

Microfluidic chips known as μ-TAS or LoC have become versatile tools in cell research, since functional biochips are able to streamline dynamic observations of various cells. Glass or polymers are generally used as the substrate due to their high transparency, chemical stability and cost-effectiveness. However, these materials are not well suited to the microscopic observation at the fluid boundary due to the refractive index mismatch between the medium and the biochip material. For this reason, we have developed a method of fabricating three-dimensional (3D) microfluidic chips made of a low refractive index fluoric polymer CYTOP. CYTOP has a refractive index of 1.34, a value that is almost equivalent to that of water. This optical property is very important for clear 3D microscopic observations of cell motion near the solid boundary, due to the minimal mismatch between the refractive index values of the medium and the CYTOP substrate. Therefore, CYTOP microfluidics are expected to allow the generation of clear images of unique cell migratory processes near the microfluidic sidewall. Therefore, we established the fabrication procedure involving the use of femtosecond laser direct writing, followed by wet etching and annealing, to create high-quality 3D microfluidics inside a polymer substrate. A microfluidic chip made in this manner enables us to more clearly observe areas near the fluid surface, compared to the observations possible using conventional microfluidic chips.

We present the fabrication of a waveguide-like structure in a polydimethylsiloxane (PDMS) polymer substrate using a femtosecond laser to study the mechanism of symbiosis between filamentous cyanobacteria, Phormidium, and a seedling root. While symbiosis occurring underground promotes the growth of vegetable seedlings, the details of the mechanism remain unclear. Understanding the mechanisms of Phormidium gliding to the seedling root will facilitate improving the mat formation of Phormidium, which will lead to increased vegetable production. We assumed a symbiosis mechanism in which sunlight propagates through the seedling root and is scattered underground to guide the Phormidium gliding. Once attached to the root, Phormidium uses the scattered light for photosynthesis. Photosynthetic products, in turn, promote an increase in Phormidium mat formation and vegetable growth. To verify this assumption, the optical characteristics of the seedling root were investigated. A waveguide-like structure with the same optical characteristics of the root was subsequently fabricated by femtosecond laser in PDMS polymer to assess the light illumination effect on Phormidium behavior.

Femtosecond lasers have unique characteristics of ultrashort pulse width and extremely high peak intensity; however, one of the most important features of femtosecond laser processing is that strong absorption can be induced only at the focus position inside transparent materials due to nonlinear multiphoton absorption. This exclusive feature makes it possible to directly fabricate three-dimensional (3D) microfluidic devices in glass microchips by two methods: 3D internal modification using direct femtosecond laser writing followed by chemical wet etching (femtosecond laser-assisted etching, FLAE) and direct ablation of glass in water (water-assisted femtosecond laser drilling, WAFLD). Direct femtosecond laser writing also enables the integration of micromechanical, microelectronic, and microoptical components into the 3D microfluidic devices without stacking or bonding substrates. This paper gives a comprehensive review on the state-of-the-art femtosecond laser 3D micromachining for the fabrication of microfluidic, optofluidic, and electrofluidic devices. A new strategy (hybrid femtosecond laser processing) is also presented, in which FLAE is combined with femtosecond laser two-photon polymerization to realize a new type of biochip termed the ship-in-a-bottle biochip.

This paper presents a simple technique to fabricate new electrofluidic devices for the three-dimensional (3D) manipulation of microorganisms by hybrid subtractive and additive femtosecond (fs) laser microfabrication (fs laser-assisted wet etching of glass followed by water-assisted fs laser modification combined with electroless metal plating). The technique enables the formation of patterned metal electrodes in arbitrary regions in closed glass microfluidic channels, which can spatially and temporally control the direction of electric fields in 3D microfluidic environments. The fabricated electrofluidic devices were applied to nanoaquariums to demonstrate the 3D electro-orientation of Euglena gracilis (an elongated unicellular microorganism) in microfluidics with high controllability and reliability. In particular, swimming Euglena cells can be oriented along the z-direction (perpendicular to the device surface) using electrodes with square outlines formed at the top and bottom of the channel, which is quite useful for observing the motions of cells parallel to their swimming directions. Specifically, z-directional electric field control ensured efficient observation of manipulated cells on the front side (45 cells were captured in a minute in an imaging area of ~160×120 μm), resulting in a reduction of the average time required to capture the images of five Euglena cells swimming continuously along the z-direction by a factor of ~43 compared with the case of no electric field. In addition, the combination of the electrofluidic devices and dynamic imaging enabled observation of the flagella of Euglena cells, revealing that the swimming direction of each Euglena cell under the electric field application was determined by the initial body angle. Devices for manipulating microorganisms have been made using a simple method involving a femtosecond laser by researchers in Japan and China. Electrofluidic devices that permit rapid 3D control of the orientation of microorganisms are important for exploring the functions of various microorganism structures. Koji Sugioka at the RIKEN Center for Advanced Photonics, Japan, and his co-workers have demonstrated that hybrid femtosecond-laser microfabrication is promising for making such devices because it enables electrodes of designable geometries to be integrated at desired locations. The researchers used the technique to make ‘nanoaquariums’ that can rapidly orientate the elongated unicellular microorganisms Euglena gracilis, allowing them to obtain desired images of Euglena cells much faster than when no electric field is applied. The team anticipates that the devices can be applied to the 3D alignment of other elongated cells.

We demonstrate laser microfabrication of transparent fluoric polymer using a conventional green laser. Fluoric polymers have unique characteristics such as high transparency, chemical resistance, and low refractive index and are expected to overcome many problems which conventional polymers have for biochip applications. We developed crack-free surface microfabrication of commercially available fluoric polymer commercially available fluoric polymer CYTOP (Asahi Glass Co., Ltd., Tokyo) using a conventional green laser. The laser ablation with successive wet etching by fluorine solution and annealing achieves high-quality microfluidics on the surface of the polymer substrate. In addition, we demonstrate the fabrication of a biochip with a three-dimensional fluid structure by bonding two pieces of CYTOP substrates for clear microscopic observation of swimming aquatic microorganism at the sidewall of the fluidics.

We demonstrate the generation of ultrabroad bandwidth attosecond continua extending to sub-50-as duration in the extreme ultraviolet (EUV) region based on a 1.6-cycle Ti:sapphire laser pulse. The combination of the amplitude gating scheme with a sub-two-cycle driver pulse and the double optical gating scheme achieves the continuum generation with a bandwidth of 70 eV at the full width at half maximum near the peak photon energy of 140 eV, which supports a Fourier-transform-limited pulse duration as short as 32 as. The carrier-envelope-phase (CEP) dependence of the attosecond continua shows a single-peak structure originating from the half-cycle cut-off at appropriate CEP values, which strongly indicates the generation of a single burst of an isolated attosecond pulse. Our approach suggests a possibility for isolated sub-50-as pulse generation in the EUV region by compensating for the intrinsic attosecond chirp with a Zr filter.

Internal modification of transparent materials such as glass can be carried out using multiphoton absorption induced by a femtosecond (fs) laser. The fs-laser modification followed by thermal treatment and successive chemical wet etching in a hydrofluoric (HF) acid solution forms three-dimensional (3D) hollow microstructures embedded in photosensitive glass. This technique is a powerful method for directly fabricating 3D microfluidic structures inside a photosensitive glass microchip. We used fabricated microchips, referred to as a nanoaquarium, for dynamic observations of living microorganisms. In addition, the present technique can also be used to form microoptical components such as micromirrors and microlenses inside the photosensitive glass, since the fabricated structures have optically flat surfaces. The integration of microfluidics and microoptical components in a single glass chip yields biophotonic microchips, in other words, optofluidics, which provide high sensitivity in absorption and fluorescence measurements of small volumes of liquid samples.

A microchip made of UV transparent polymer (CYTOP) that can perform selective cell culture has been fabricated by F2 laser surface modification. The refractive index of CYTOP is almost the same as that of culture medium, which is essential for three-dimensional (3D) observation of cells. The F2 laser modification of CYTOP achieves hydrophilicity only on the laser irradiated area with little deterioration of the optical properties and surface smoothness. After the laser modification, HeLa cells were successfully cultured and strongly adhered only on the modified area of CYTOP. The cells patterned on CYTOP were applied for clear 3D observation using an optical microscope in phase contrast mode.

We demonstrate fabrication of microchips with microfluidic structures for dynamic analysis of living cells using a femtosecond (fs) laser. Fs laser direct writing followed by annealing and successive wet etching in dilute hydrofluoric (HF) acid solution resulted in formation of three dimensional (3D) hollow microstructures embedded in photostructurable glass. The embedded microchannel structure enabled us to analyze unique phenomenon of Cryptomonas, which suddenly swims very fast under certain condition. Vector analysis of the driving force for the rapid motion was also carried out by introducing nano-beads into the microchannel, in which Cryptomonas was encapsulated. We also fabricated a microchip for observation of Phormidium moving toward a seedling root, which accelerates growth of the seedling. Using the embedded microchannel in the microchip, observation of Phormidium assemblage to the seedling root was easily carried out. Such microchips with microfluidic structures, referred to as a nano-aquarium, realize the efficient and highly functional observation of living cells.

Three-dimensional (3D) microfabrication of photostruc- turable glass by femtosecond (fs) laser direct writing is demonstrated for manufacture of biophotonic microchips. The fs laser direct writ- ing followed by annealing and successive wet etching can fabricate the hollow microstructures, achieving a variety of microfluidic components and microoptical components in a glass chip. One of the interesting and important applications of the 3D microfluidic structures fabricated by the present technique is inspection of living microorganisms. The microchips used for this application are referred to as nanoaquarium. Furthermore, the optical waveguide is written inside the glass by the fs laser direct writing without the annealing and the successive etching. It is revealed that integration of the microfluidic and microoptical com- ponents with the optical waveguides in a single glass chip is of great use for biochemical analysis and medical inspection based on optical sensing.

We demonstrate the fabrication of three-dimensional (3-D) hollow microstructures embedded in photostructurable glass by a femtosecond (fs) laser direct writing. Fs laser direct writing followed by annealing and successive wet etching in dilute hydrofluoric (HF) acid solution resulted in the rapid manufacturing of microchips with 3-D hollow microstructures for the dynamic observation of living microorganisms in fresh water. The embedded microchannel structure enables us to analyze the continuous motion of flagellum movement of Euglena gracilis. Such microchips, referred to as nano-aquariums realize the efficient and highly functional observation of microorganisms.

We report the surface microfabrication of CYTOP, an amorphous UV transparent fluoric polymer, using a conventional pulsed green laser. Fluorine-based polymers have unique characteristics, including high transparency from the deep-UV to the IR wavelengths, chemical stability and low refractive indices, and thus are expected to have a number of industrial applications. However, CYTOP and other fluoric polymers are generally very difficult to microfabricate. Therefore, we have developed a technique for the crack-free surface microfabrication of a CYTOP substrate based on ablation with a pulsed green laser followed by successive wet etching and annealing. In this work, the fundamental surface characteristics of the fabricated area were investigated. Following the surface microfabrication of CYTOP, a three-dimensional biochip was fabricated using a conventional bonding technique to demonstrate that a CYTOP biochip is superior to conventional transparent biochips with regard to the microscopic observation of cell motion.

We demonstrate an isolated attosecond pulse generation based on the double optical gated 4.7 fs driving laser. The generated supercontinuum spectrum has an extremely broad bandwidth of 70 eV, which supports 32-as duration.

We report the selective metallization of photostructurable glass by femtosecond (fs) laser direct writing followed by electroless copper (Cu) plating. It was found that a Cu thin film can be deposited only on the rough surface of glass ablated by the fs laser. The deposited Cu thin film exhibits strong adhesion and excellent electrical properties. A Cu film can even be deposited on the internal wall of a hollow microchannel inside photostructurable glass by the multiphoton absorption of the fs laser. To show the use of this technique for micro-total-analysis-system (μ-TAS) applications, the fabrication of a microheater operating at temperatures up to 200 °C was demonstrated.

Photosensitive glass is a potentially important material for micro-fluidic devices that can be integrated with micro-optical components for biochemical analysis. Here, we demonstrate the fabrication of optical waveguides inside glass by femtosecond laser direct writing. The influence of the laser parameters on the waveguide properties is investigated, and it is revealed that the waveguide mode can be well controlled. The single mode is achieved at a low writing energy, while the multimode is achieved with increasing energy. In spite of a longitudinally elongated elliptical shape of the cross-sectional profile, the far-field pattern of the single-mode waveguide shows an almost symmetric profile. The measured propagation loss and the coupling loss are evaluated to be ∼0.6 dB/cm and ∼1.6 dB at a wavelength of 632.8 nm, respectively, under the conditions of 1.0–2.0 μJ pulse energy and 200–500 μm/s scan speed. The increased optical loss is associated with a higher waveguide mode at higher writing energy. Furthermore, the integration of waveguides and a micromirror made of a hollow microplate inside the glass is demonstrated to bend the laser beam at an angle of 90° in a small chip. The bending loss is estimated to be smaller than 0.3 dB.

3D integration of microcomponents in a single glass chip by femtosecond laser direct writing followed by post annealing and successive wet etching is described for application to biochemical analysis. Integration of microfluidics and microoptics realized some functional microdevices like a μ-fluidic dye laser and a biosensor. As one of practical applications, we demonstrate inspection of living microorganisms using the microchip with 3D microfluidic structures fabricated by the present technique.

We demonstrate colour marking of a transparent material using laser-induced plasma-assisted ablation (LIPAA) system. After the LIPAA process, metal thin film is deposited on the surface of the ablated groove. This feature is applied to RGB (red, green and blue) colour marking by using specific metal targets. The metal targets, for instance, are Pb3O4 for red, Cr2O3 for green and [Cu(C32H15ClN8)] for blue colour marking. Additionally, adhesion of the metal thin film deposited on the processed groove by various experimental conditions is investigated.

In this paper first experimental results are presented on the fabrication of integrated-optical microstructures by femtosecond-laser irradiation at the surface or in the volume of a polymeric substrate. Thereby the refractive index or the optical absorption coefficient of the polymer material is locally modified in a controllable way due to nonlinear optical effects like multi-photon absorption. By this way surface relief grating structures, volume grating structures and linear waveguiding structures are generated. The surface relief gratings have diffraction efficiencies about 0.2 (first diffraction order), the diffraction efficiencies of the volume gratings are approximately smaller by one order of magnitude. Besides experiments have been performed on the modification of the polymeric surface by fs-laser irradiation followed by subsequent development of the irradiated area by an etching liquid generating linear groove structures. By this way simple linear microstructures are generated into the polymer substrate. The results of these experiments are relevant for the fabrication of three-dimensional structures in the polymeric substrate in the future. All the gratings and the linear microstructures can be considered as basic components for the fabrication of complex micro-optical and fluidic systems in a polymeric substrate (photonic lab-on-the-chip).

Polymers are modified by femtosecond-(fs)-IR-laser irradiation under various process parameters. Several sorts of thermoplastic polymer are employed: polymethylmethacrylate (PMMA), fluorinated PMMA, poly-N-methyl methacrylimide (PMMI), polystyrol, polycarbonate, polyimide, and polyethylene. After the fs-laser-induced modification process, the irradiated area is developed by an aqueous solution of a solvent agent (n-hexane, benzene, and methylisobutylketone). The surface topography of the fs-laser-irradiated area is characterized by stylus-profilometry before and after the development procedure. Some preliminary explanations are given about the solution mechanism of the fs-laser-irradiated polymer region. The experimental results are relevant for the fabrication of three-dimensional (3D)-structures in the volume of a transparent polymer material by fs-laser irradiation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1229–1238, 2006

Double-pulse irradiation using a near-IR femtosecond laser (λ = 775 nm) was used to study the mechanism of the laser-induced plasma-assisted ablation (LIPAA) process. The dependence of the ablation depth on the delay time between the first and the second pulse for various target-to-substrate distances was investigated. The first pulse generates the laser-induced plasma from the metal target, but does not induce ablation of the glass substrate. The second pulse induces the high-efficiency ablation of the substrate, delayed by several nanoseconds (ns). A possible mechanism of the conventional LIPAA process using a ns pulsed laser is discussed based on the obtained results.

We report micromachining of polyimide (PI) by laser-induced plasma-assisted ablation (LIPAA) using a fundamental wavelength of a commercial Q-switched Nd : YAG laser (1064 nm). It is found that an Au film on a glass target is effective for the LIPAA process of PI. The ablation rate reaches several tens of nanometers per pulse. After the LIPAA process, selective metallization of PI with excellent electrical properties is performed by successive electroless Cu plating. The Cu line width of 40 μm, which agrees with the line width of regions ablated by the LIPAA process, is achieved using an encapsulated film.

The enhancement of tunneling probability in the nearly integrable system is closely examined, focusing on tunneling splittings plotted as a function of the inverse of the Planck's constant. On the basis of the analysis using the absorber which efficiently suppresses the coupling creating spikes in the plot, we found that the splitting curve should be viewed as the staircase-shaped skeleton accompanied by spikes. We further introduce renormalized integrable Hamiltonians, and explore the origin of such a staircase structure by investigating the nature of eigenfunctions closely. It is found that the origin of the staircase structure could trace back to the anomalous structure in tunneling tail which manifests itself in the representation using renormalized action bases. This also explains the reason why the staircase does not appear in the completely integrable system.

We propose a new technique for quantitative trajectory analysis of gliding phenomenon of Navicula pavillardii (NP) and Seminavis robusta (SR) diatom cells by single cell observation using a glass microchamber in this short technical note. Two-dimensional trajectory analysis of cell movements was used to determine the angular velocity, velocity, and migration distances of the diatom movement. Based on the trajectory analysis, we found that asymmetrically shaped SR had a larger angular velocity with large fluctuations compared to symmetrically shaped NP, although the velocity of SR was less than that of NP. It suggests that lateral frictional force in a culture medium is an important factor for diatom movements. Our results revealed that the single cell observation using a glass microchamber is effective on quantitative analysis of angular velocity of diatom gliding.

The laser-induced plasma-assisted ablation (LIPAA) process developed by us, in which only a single conventional pulsed laser is used, makes it possible to perform high-quality and high-speed glass microfabrication. We developed the LIPAA system, which uses the second harmonic of a diode pumped Q-switched Nd:YAG laser, for practical use in industry. The system comprises two optical components, which are the objective lens for high-resolution microfabrication and the galvano mirror type scanner for high-speed patterning of complicated microstructures. In addition to surface microstructuring of the glass, selective metallization of the glass by the LIPAA process, followed by electroless Cu plating, is demonstrated .

The demand for increased sensitivity in the concentration analysis of biochemical liquids is a crucial issue in the development of lab on a chip and optofluidic devices. We propose a new design for optofluidic devices for performing highly sensitive biochemical liquid assays. This design consists of a microfluidic channel whose internal walls are coated with a polymer and an optical waveguide embedded in photostructurable glass. The microfluidic channel is first formed by three-dimensional femtosecond laser micromachining. The internal walls of the channel are then coated by the dipping method with a polymer that has a lower refractive index than water. Subsequently, the optical waveguide is integrated with the microfluidic channel. The polymer coating on the internal walls permits the probe light, which is introduced by the optical waveguide, to propagate along the inside of the microfluidic channel. This results in a sufficiently long interaction length between the probe light and a liquid sample in the channel and thus significantly improves the sensitivity of absorption measurements. Using the fabricated optofluidic chips, we analyzed protein in bovine serum albumin to concentrations down to 7.5 mM as well as 200 nM glucose-D.

We demonstrate fabrication of microfluidic chips integrated with optical waveguide embedded in a photostructurable glass for high-sensitive biochemical liquid analysis using a femtosecond laser. Femtosecond laser direct writing followed by annealing and successive wet etching in hydrofluoric acid solution resulted in the rapid manufacturing of microfluidic chips for the biochemical liquid concentration assay. By covering the internal wall of the microfluidic channel in the glass with low refractive index polymer, interaction between the liquid and incident analyzing light is enhanced. Therefore, the microfluidic chip enables us to analyze the low concentrations down to 7.5 mM of protein in bovine serum albumin. Such microfluidic chip realizes the efficient and high-sensitive concentration analysis of biochemical liquids at early stages of biochemical reactions.

We employ manipulated ultrafast laser pulses to realize microprocessing with high-performance. Efficient microwelding of glass substrates by irradiation by a double-pulse train of ultrafast laser pulses is demonstrated. The bonding strength of two photostructurable glass substrates welded by double-pulse irradiation was evaluated to be 22.9 MPa, which is approximately 22% greater than that of a sample prepared by conventional irradiation by a single pulse train. Additionally, the fabrication of hollow microfluidic channels with a circular cross-sectional shape embedded in fused silica is realized by spatiotemporally focusing the ultrafast laser beam. We show both theoretically and experimentally that the spatiotemporal focusing of ultrafast laser beam allows for the creation of a three-dimensionally symmetric spherical peak intensity distribution at the focal spot.