Kenji Goya

A capillary flow immunoassay microchip utilizing inkjet printing-based antibody immobilization onto island surfaces—toward sensitive and reproducible determination of carboxyterminal propeptide of type I procollagen

A capillary-flow-driven microchip system requires no external power and has no moving off-chip components, in contrast with most microfluidic-based immunoassay systems which are complicated to operate and require external components. To accelerate the sensitive and reproducible determination of analytes required for practical point-of-care applications, we formed island microchannel surfaces on a microcapillary channel to allow stable antibody immobilization. The island surface was surrounded by a circular groove 10 μm deep and 150 μm wide and allowed uniform inkjet printing of antibody spots, complete bio-reagent replacement, and sensitive detection of luminescence intensity. Quantitative analysis of carboxyterminal propeptide of type I procollagen (PICP) concentrations using this microchannel was demonstrated between 0–600 ngml−1, which is adequate for the clinical estimation of PICP concentrations in the blood. This microchip system holds promise as a model diagnostic platform that is readily adaptable to hands-free operation.

Paper-like Surface Microstructure Fabricated on a Polymer Surface by Femtosecond Laser Machining (A SPECIAL ISSUE ON PAPER-BASED ANALYTICAL DEVICES)

In this study, we demonstrate the precise control of fluid flow using femtosecond (FS) laser-induced microstructures. A microgroove structure inscribed on a poly(methyl methacrylate) (PMMA) substrate functions as a superhydrophilic membrane similar to paper. We first estimated the flow rate for pure water on microgrooves fabricated at various laser fluences in the range from 9.2 to 100.8 J/cm2. The results showed that the flow rate could be tuned in the range from 0.30 to 12.07 μL/s by varying the laser irradiation parameters. The fluid flow was reproducible, with a calculated relative standard deviation (RSD%) of less than 8% in the flow rate. We then fabricated a microfilter for blood separation and estimated its filtration ability using artificial blood containing resin microparticles. This method would be useful in a technology related to a paper-based diagnostic device for precise reagent manipulation.

Practical High-Performance Lateral Flow Assay Based on Autonomous Microfluidic Replacement on a Film

Although paper-based microfluidic devices are an ideal platform for point-of-care (POC) diagnostics, it is difficult to achieve microfluidic control required for sensitive analyses such as ELISA on a paper substrate. Here, we present a novel lateral-flow test chip that can perform operations similar to a pump, such as flowing, stopping, and replacing a solution, just by adding the solution onto an inlet port. The chip was fabricated by laminating paper, film, and adhesive tape. For sensitive and accurate detection in an immunoassay, the transparency and flatness of the substrate is crucial for precise analysis of weak light generated by a specific antigen-antibody reaction; however, paper is not flat and is opaque. Therefore, transparent film was applied to the detection area of the chip in this study. The chip showed a good correlation at 0.1 - 100 ng ml-1 concentrations of C-reactive protein, demonstrating high quantitative analysis of CRP in serum suitable for clinical trials. The signal intensity of the novel chip was higher than that of a chip made of nitrocellulose membrane, and the variation was smaller. The limit of detection of the chip was 0.1 ng ml-1, whereas that of the nitrocellulose membrane was 100 ng ml-1. This novel chip can be used for sensitive sandwich immunoassays just by adding solutions.

Fabrication of scattering source for an optical fiber sensor using femtosecond laser internal processing

Micro-processing by using an ultrashort pulsed laser has been previously reported and developed in the past decade for fabricating micro devices. Using tightly focused short pulse laser beam, the laser intensity easily can reach more than 1013 W/cm2. Under such conditions non-linear phenomena are triggered, hence multiphoton ionization and self-focusing are notably induced in a medium. Femtosecond laser enables micro-fabrication without critical heat damage owing to extremely shorter pulse width and very fast multi-photon absorption at the laser focal point, compared with longer pulse irradiation. In this report, a micro-voids array was created in optical fiber line by using a femtosecond laser to produce sensing area only at local micro-region of the fiber line. At sensing portion consisted of the voids array, transmitted light was partially scattered by voids after that the leaked light could be reflected on the interface of cladding and outsides, which held the incident angle depending on structures of the micro-voids array. Voids array played as a role of scattering sources to transmitted light and consequently it was expected that the transmitted light can be broadly leaked out from the fiber core to the cladding. Furthermore, optical losses attributed to the creation of micro voids were quantitatively obtained so as to figure out the sensor characteristics. Consequently the reflection region which was considered as a sensing area showed the re-coupling rate of 0.04 dB (3.03%) to insertion loss of 1.32 dB, and the incident angle existed between 67.2 -71.9°.

An LSPR fiber optic sensor based on in-line micro-holes fabricated by a second harmonic 400nm femtosecond laser

In this study, we have proposed a novel type of localized surface plasmon resonance (LSPR) fiber optic sensor based on in-line/pico-liter micro-holes which can be experimentally fabricated into the fiber waveguide by using a second harmonic 400 nm femtosecond laser. A repetitive pulse train of 1 kHz with a pulse width of 350 fs was irradiated onto a MMGI fiber optic to make three holes that penetrate through the fiber core and work as spectroscopic-microfluidic flow cells. In order to induce the interaction between transmitted light and gold nanoparticles (GNPs) adhered on the inner surface of the flow cells, micro-holes were designed to be the width of approximately 50 μm, along a direction perpendicular to an optical axis of an optical fiber. GNPs with approximately 100 nm of particle diameter adhered onto the inner surface according to 3-aminopropyltriethoxy silane treatment. The transmitted light through the micro-holes was obtained by optical instruments consisted of a white light source and an optical spectrum analyzer. In order to obtain the reference spectrum, the optical spectrum was acquired before dipping the sensor into the GNPs solution. After 30 min of immersing the sensor portion into the GNPs solution, the optical spectrum was also obtained. The reference spectrum which was considered as the baseline, was set to zero and then, the absorbance spectrum was calculated. The absorbance peak at a wavelength of 537 nm occurred in an air condition in the sensing area, which seemed like the resonance peak based on the LSPR.

Femtosecond Laser-Induced Surface Modification and its Application

In this chapter, we present femtosecond laser micromachining to fiber optics, focusing on surface qualities. Some techniques applied in the field are introduced to date and a review of some of the current applications for this type of technology. Section 2 describes laser-induced periodic surface structures (LIPSSs), which are induced in lowand highfluence regime. Section 3 describes the influences of laser-induced structures for the fabrication of fiber-optic sensors, with experimental techniques and results in our research group. These sections explore ultrashort laser pulses applications, roughly going from lower to higher energy (power, intensity) ones.

Femtosecond Laser Internal Processing for an Optical Fiber Sensor Inducing Interference of Optical Waveguide

A new optical fiber sensing structure was proposed by using femtosecond laser internal processing. The proposed sensor was composed of cavity regions (voids) fabricated by focused ultra-short pulse laser beam in line at the interface of optical fiber between core and cladding. Cladding-modes was induced by scattering propagation light at voids, and caused interference of core and cladding modes after interacting with external materials around the optical fiber. Induced interference spectrum was shifted due to refractive index of surrounding materials. Through some experiments interference spectrum was observed with having amplitude more than 0.20 dB. The sensitivity of proposed sensor has been achieved to reach 31.8 nm/RIU for a RI range of 1.000–1.333. The interference spectrum was ascertainable when the sensor portion was in air and immersed into pure water, but not gained when sensor portion was immersed into mediums having relatively higher RI.