Design, fabrication and characterization of monolithic embedded parylene microchannels in silicon substrate

This paper presents a novel channel fabrication technology of bulk-micromachined monolithic embedded polymer channels in silicon substrate. The fabrication process favorably obviates the need for sacrifical materials in surface-micromachined channels and wafer-bonding in conventional bulk-micromachined channels. Single-layer-deposited parylene C (poly-para-xylylene C) is selected as a structural material in the microfabricated channels/columns to conduct life science research. High pressure capacity can be obtained in these channels by the assistance of silicon substrate support to meet the needs of high-pressure loading conditions in microfluidic applications. The fabrication technology is completely compatible with further lithographic CMOS/MEMS processes, which enables the fabricated embedded structures to be totally integrated with on-chip micro/nano-sensors/actuators/structures for miniaturized lab-on-a-chip systems. An exemplary process was described to show the feasibility of combining bulk micromachining and surface micromachining techniques in process integration. Embedded channels in versatile cross-section profile designs have been fabricated and characterized to demonstrate their capabilities for various applications. A quasi-hemi-circular-shaped embedded parylene channel has been fabricated and verified to withstand inner pressure loadings higher than 1000 psi without failure for micro-high performance liquid chromatography (µHPLC) analysis. Fabrication of a high-aspect-ratio (internal channel height/internal channel width, greater than 20) quasi-rectangular-shaped embedded parylene channel has also been presented and characterized. Its implementation in a single-mask spiral parylene column longer than 1.1 m in a 3.3 mm × 3.3 mm square size on a chip has been demonstrated for prospective micro-gas chromatography (µGC) and high-density, high-efficiency separations. This proposed monolithic embedded channel technology can be extensively implemented to fabricate microchannels/columns in high-pressure microfludics and high-performance/high-throughput chip-based micro total analysis systems (µTAS)

EFFECTS ON POSTURAL CONSTRAINTS ON OVERARM THROWING

This study explored the effects of postural constraints on overarm throwing. 10 participants were required to perform an overarm throwing movement by 3 tasks which under postural constraints. Tasks were including trunk-fixed, sitting, and standing. 10 pieces of 3D motion capture system were used to record the maximum velocity of body segments as data and one-way repeated measures ANOVA (a=.05) with HSD post-hoc tests was conducted to analysis the data. Therefore, the results indicated that the performance of overarm throwing by 3 tasks were different significantly, which proved the kinetic chain formed by links connected in series gave body segments more velocities. Moreover, it meat trunk and lower limbs played the roles to transport velocity as performing overarm throwing

Parylene-strengthened thermal isolation technology for microfluidic system-on-chip applications

Here we reported a novel technology using parylene-cross-linking structure to achieve on-chip air-gap thermal isolation for microfluidic system-on-chip (SOC) applications. Two applications based on this technology, on-chip continuous-flow polymerase chain reaction (PCR) and on-chip temperature gradient liquid chromatography (LC) were successfully demonstrated. Device thermal performance in each example was characterized. Results showed that our technology not only provides excellent on-chip thermal isolation but also its simplicity of integration with other on-chip components makes versatile microfluidic SOC applications feasible

The Effects of Firm-Initiated Clawback Provisions on Earnings Quality and Auditor Behavior

While firm-initiated compensation recovery (or clawback) provisions are gaining popularity and the recently enacted Dodd-Frank Act seeks to make the clawback of erroneously awarded compensation mandatory for all listed companies, little is known about their effectiveness. We find that the incidence of accounting restatements declines after firms initiate such provisions. In addition, we show that investors and auditors view such provisions as associated with increased accounting quality and lower audit risk. Specifically, we find that firms' earnings response coefficients increase after the adoption of clawback provisions. Further, for firms that adopt clawbacks, auditors are less likely to report material internal control weaknesses, charge lower audit fees, and issue audit reports with a shorter lag

Resonance-induced sensitivity enhancement method for conductivity sensors

Methods and systems for improving the sensitivity of a variety of conductivity sensing devices, in particular capacitively-coupled contactless conductivity detectors. A parallel inductor is added to the conductivity sensor. The sensor with the parallel inductor is operated at a resonant frequency of the equivalent circuit model. At the resonant frequency, parasitic capacitances that are either in series or in parallel with the conductance (and possibly a series resistance) is substantially removed from the equivalent circuit, leaving a purely resistive impedance. An appreciably higher sensor sensitivity results. Experimental verification shows that sensitivity improvements of the order of 10,000-fold are possible. Examples of detecting particulates with high precision by application of the apparatus and methods of operation are described

Yield strength of thin-film parylene-C

For the first time, the yield strength of thin-film parylene-c is measured from membrane load-deflection experiments and surface profile analysis. To do so, the onset pressure which causes plastic deformation of the membrane is first experimentally measured. Then a new 2-step displacement model, together with the energy minimization technique, is developed to convert the onset pressure to the yield strength on the pre-stressed parylene membrane under a uniform pressure loading. The results depict a Yield Strength of 59 MPa (or 0.012 of strain) for thin-film parylene-c in comparison to 55 MPa reported by parylene vendor (measured from large samples). To double check with the result, the balloon model is further used to compare with the stress value from our model at the center of parylene membranes and good agreements are obtained

Nanometer gaps by feedback-controlled electromigration

Nanometer-sized gap (or nanogap) is one of the most fundamental devices in the nanotechnology field. Park et. al., first proposed the open-circuit electromigration method to fabricate nanogaps, but the process is only repeatable if Au film is thinner than 20 nm. To overcome these drawbacks, we develop the feedback-controlled electromigration process and find that not only repeatable nanogaps can be created in thicker film (up to 120 nm or thicker in our experiments), but superior gap size control and topology are obtained. Moreover, we develop two new approaches to make free-standing nanogaps. The tunneling current between the nanogap electrodes was used to demonstrate a sensitive pressure and/or temperature sensor. Finally, we also develop a simple thermal-expansion method to measure the gap size without needing delicate instrument

Surface-Assisted Laser Desorption/Ionization Mass Spectrometry on Titania Nanotube Arrays

Titania nanotube arrays (NTA) generated from anodizing processes are tested as the substrate for surface-assisted laser desorption/ionization mass spectrometry (SALDI MS). The background generated from titania NTA is very low, making the approach suitable for the analysis of small molecules. The upper detectable mass is ∼29 kDa. Homogeneous sample deposition leads to good shot-to-shot reproducibility and suitability for quantitative analysis. Additionally, phosphopeptides can be selectively trapped on the titania NTA substrate, as illustrated by simply depositing a tryptic digest of β-casein followed by titania NTA SALDI MS analysis. The detection limit for small organics and peptides is in low fmol

A Community-Based Walk-In Screening of Depression in Taiwan

Depression is a crucial public health problem because of its relatively high association with suicidal attempts, prolonged social isolation, poor physical health, and dementia. However, the available data and study on the prevalence of depression in Taiwan were mostly completed within the previous 1 to 2 decades, and these studies were limited to certain areas or populations. Little is known regarding the current status of depression in Taiwan. We used a brief tool, the Center for Epidemiological Studies Depression Scale (CES-D), to screen depression in 4 areas among the general and aged population. The results showed a higher CES-D score in the southern area among general (mean ± SD: 7.8 ± 8.4) or aged participants (mean ± SD: 7.2 ± 8.0) compared with other areas. The ratio of suspected depression patients was 16.4% of all recruited participants and 13.3% of aged participants. These results may provide information for this public health issue