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)

Singing voice correction using canonical time warping

Expressive singing voice correction is an appealing but challenging problem. A robust time-warping algorithm which synchronizes two singing recordings can provide a promising solution. We thereby propose to address the problem by canonical time warping (CTW) which aligns amateur singing recordings to professional ones. A new pitch contour is generated given the alignment information, and a pitch-corrected singing is synthesized back through the vocoder. The objective evaluation shows that CTW is robust against pitch-shifting and time-stretching effects, and the subjective test demonstrates that CTW prevails the other methods including DTW and the commercial auto-tuning software. Finally, we demonstrate the applicability of the proposed method in a practical, real-world scenario

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

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

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

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

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