Investigation of strain sensing effect in modified single-defect photonic crystal nanocavity.

This paper reports the theoretical and experimental investigations on the strain sensing effect of a two dimensions (2D) photonic crystal (PhC) nanocavity resonator. By using the finite element method (FEM) and finite difference time domain (FDTD) simulations, the strain sensitivity of a high quality factor PhC nanocavity was calculated. Linear relationships between the applied strain and the shift in the resonant wavelength of the cavity were obtained. A single-defect silicon (Si) PhC cavity was fabricated, and measurements of the strain sensitivity were performed. Good agreement between the experimental and simulation results was observed.

Electrochemical selective detection of uric acid using a copper-modified carbon electrode.

The uric acid (UA) level in (human) serum is an important indicator of several diseases; however, its electrochemical detection is difficult because the oxidation potentials of UA and ascorbic acid (AA) are very close. In this study, we have developed a simple and efficient UA detection method using a copper-modified carbon electrode. The detection principle is based on the selective oxidation of AA by Cu(II), wherein Cu(II) reacts selectively with AA but not with UA. By performing this specific reaction on an electrode surface, we have successfully distinguished the oxidation potential of UA without AA interference.

Designing of a Si-MEMS device with an integrated skeletal muscle cell-based bio-actuator.

With the aim of designing a mechanical drug delivery system involving a bio-actuator, we fabricated a Micro Electro Mechanical Systems (MEMS) device that can be driven through contraction of skeletal muscle cells. The device is composed of a Si-MEMS with springs and ratchets, UV-crosslinked collagen film for cell attachment, and C2C12 muscle cells. The Si-MEMS device is 600 µm x 1000 µm in size and the width of the collagen film is 250 ~ 350 µm, which may allow the device to go through small blood vessels. To position the collagen film on the MEMS device, a thermo-sensitive polymer was used as the sacrifice-layer which was selectively removed with O2 plasma at the positions where the collagen film was glued. The C2C12 myoblasts were seeded on the collagen film, where they proliferated and formed myotubes after induction of differentiation. When C2C12 myotubes were stimulated with electric pulses, contraction of the collagen film-C2C12 myotube complex was observed. When the edge of the Si-MEMS device was observed, displacement of ~8 µm was observed, demonstrating the possibility of locomotive movement when the device is placed on a track of adequate width. Here, we propose that the C2C12-collagen film complex is a new generation actuator for MEMS devices that utilize glucose as fuel, which will be useful in environments in which glucose is abundant such as inside a blood vessel.

Development of an alternating magnetic-field-assisted finishing process for microelectromechanical systems micropore x-ray optics.

X-ray astronomy research is often limited by the size, weight, complexity, and cost of functioning x-ray optics. Micropore optics promises an economical alternative to traditional (e.g., glass or foil) x-ray optics; however, many manufacturing difficulties prevent micropore optics from being a viable solution. Ezoe et al. introduced microelectromechanical systems (MEMS) micropore optics having curvilinear micropores in 2008. Made by either deep reactive ion etching or x-ray lithography, electroforming, and molding (LIGA), MEMS micropore optics suffer from high micropore sidewall roughness (10-30nmrms) which, by current standards, cannot be improved. In this research, a new alternating magnetic-field-assisted finishing process was developed using a mixture of ferrofluid and microscale abrasive slurry. A machine was built, and a set of working process parameters including alternating frequency, abrasive size, and polishing time was selected. A polishing experiment on a LIGA-fabricated MEMS micropore optic was performed, and a change in micropore sidewall roughness of 9.3+/-2.5nmrms to 5.7+/-0.7nmrms was measured. An improvement in x-ray reflectance was also seen. This research shows the feasibility and confirms the effects of this new polishing process on MEMS micropore optics.

Versatile microfluidic total internal reflection (TIR)-based devices: application to microbeads velocity measurement and single molecule detection with upright and inverted microscope.

A poly(dimethylsiloxane) (PDMS) chip for Total Internal Reflection (TIR)-based imaging and detection has been developed using Si bulk micromachining and PDMS casting. In this paper, we report the applications of the chip on both inverted and upright fluorescent microscopes and confirm that two types of sample delivery platforms, PDMS microchannel and glass microchannel, can be easily integrated depending on the magnification of an objective lens needed to visualize a sample. Although any device configuration can be achievable, here we performed two experiments to demonstrate the versatility of the microfluidic TIR-based devices. The first experiment was velocity measurement of Nile red microbeads with nominal diameter of 500 nm in a pressure-driven flow. The time-sequenced fluorescent images of microbeads, illuminated by an evanescent field, were cross-correlated by a Particle Image Velocimetry (PIV) program to obtain near-wall velocity field of the microbeads at various flow rates from 500 nl/min to 3000 nl/min. We then evaluated the capabilities of the device for Single Molecule Detection (SMD) of fluorescently labeled DNA molecules from 30 bp to 48.5 kbp and confirm that DNA molecules as short as 1105 bp were detectable. Our versatile, integrated device could provide low-cost and fast accessibility to Total Internal Reflection Fluorescent Microscopy (TIRFM) on both conventional upright and inverted microscopes. It could also be a useful component in a Micro-Total Analysis System (micro-TAS) to analyze nanoparticles or biomolecules near-wall transport or motion.

Transcriptome analysis device based on liquid phase detection by fluorescently labeled nucleic acid probes.

Personalized medicine based on genetic information has been proposed as an attractive medical treatment. It is supported by the rapid development of the gene diagnosis utilizing on-chip analysis technology. This study reports characterizations of mRNA detection device by its hybridization with 2'-O-methyl oligoribonucleotide probe in a liquid phase, which eliminates time-consuming processes such as removing non-hybridized probes in conventional solid phase detection. In order to achieve a high sensitivity in the fluorescent detection of the target mRNA, we have optimized detection channel depth and width for a microfluidic device, and investigated polydimethyl siloxiane components and observation setup to minimize background noise. Adopting optimized channel dimensions and setup for the probe, the fluorescent intensity increased 3.3-fold at the lowest detectable concentration of 7.8 nM.