The current paper describes the design, fabrication, and testing of a micromachined submicroliter-volume polymerase chain reaction (PCR) chip with a fast thermal response and very low power consumption. The chip consists of a bulk-micromachined Si component and hot-embossed poly(methyl methacrylate)(PMMA) component. The Si component contains an integral microheater and temperature sensor on a thermally well-isolated membrane, while the PMMA component contains a submicroliter-volume PCR chamber, valves, and channels. The micro hot membrane under the submicroliter-volume chamber is a silicon oxide/silicon nitride/silicon oxide (O/N/O) diaphragm with a thickness of 1.9 microm, resulting in a very low thermal mass. In experiments, the proposed chip only required 45 mW to heat the reaction chamber to 92 degrees C, the denaturation temperature of DNA, plus the heating and cooling rates are about 80 degrees C s(-1) and 60 degrees C s(-1), respectively. We validated, from the fluorescence results from DNA stained with SYBR Green I, that the proposed chip amplified the DNA from vector clone, containing tumor suppressor gene BRCA 1 (127 base pairs at 11th exon), after 30 thermal cycles of 3 s, 5 s, and 5 s at 92 degrees C, 55 degrees C, and 72 degrees C, respectively, in a 200 nL-volume chamber. As for specificity of DNA products, owing to difficulty in analyzing the very small volume PCR results from the micro chip, we vicariously employed the larger volume PCR products after cycling with the same sustaining temperatures as with the micro chip but with much slower ramping rates (3.3 degrees C s(-1) when rising, 2.5 degrees C s(-1) when cooling) within circa 20 minutes on a commercial PCR machine and confirmed the specificity to BRCA 1 (127 base pairs) with agarose gel electrophoresis. Accordingly, the fabricated micro chip demonstrated a very low power consumption and rapid thermal response, both of which are crucial to the development of a fully integrated and battery-powered instrument for a lab-on-a-chip DNA analysis.

Because of their broad applications in biomedical analysis, integrated, polymer-based microdevices incorporating micropatterned metallic and insulating layers are significant in contemporary research. In this study, micropatterns for temperature sensing and microelectrode sets for electroanalysis have been implemented on an injection-molded thin polymer membrane by employing conventional semiconductor processing techniques (i.e., standard photolithographic methods). Cyclic olefin copolymer (COC) is chosen as the polymer substrate because of its high chemical and thermal stability. A COC 5-in. wafer (1-mm thickness) is manufactured using an injection molding method, in which polymer membranes (approximately 130 microm thick and 3 mm x 6 mm in area) are implemented simultaneously in order to reduce local thermal mass around micropatterned heaters and temperature sensors. The highly polished surface (approximately 4 nm within 40 microm x 40 microm area) of the fabricated COC wafer as well as its good resistance to typical process chemicals makes it possible to use the standard photolithographic and etching protocols on the COC wafer. Gold micropatterns with a minimum 5-microm line width are fabricated for making microheaters, temperature sensors, and microelectrodes. An insulating layer of aluminum oxide (Al2O3) is prepared at a COC-endurable low temperature (approximately 120 degrees C) by using atomic layer deposition and micropatterning for the electrode contacts. The fabricated microdevice for heating and temperature sensing shows improved performance of thermal isolation, and microelectrodes display good electrochemical performances for electrochemical sensors. Thus, this novel 5-in. wafer-level microfabrication method is a simple and cost-effective protocol to prepare polymer substrate and demonstrates good potential for application to highly integrated and miniaturized biomedical devices.

Foot-and-mouth disease virus (FMDV) is a highly contagious disease that affects cloven-hoofed animals. The traditional diagnostic methods for FMDV have several drawbacks such as cross-reactivity, low sensitivity, and low selectivity. To overcome these drawbacks, we present an optical and electrochemical dual-modal approach for the specific detection of FMDV serotypes O and A by utilizing a magnetic nanoparticle labeling technique with resorufin β-d-glucopyranoside (res-β-glc) and β-glucosidase (β-glc), without the use of typical lateral flow assay or polymerase chain reaction. FMDV serotypes O and A were reacted with pan-FMDV antibodies that recognize all seven FMDV serotypes (O, A, C, Asia 1, SAT 1, SAT 2, and SAT 3). The antigen–antibody complex was then immobilized on magnetic nanoparticles and reacted with β-glc-conjugated FMDV type O or type A antibodies. Subsequently, the addition of res-β-glc resulted in the release of fluorescent resorufin and glucose owing to catalytic hydrolysis by β-glc. The detection limit of fluorescent signals using a fluorescence spectrophotometer was estimated to be log(6.7) and log(5.9) copies/mL for FMDV type O and A, respectively, while that of electrochemical signals using a glucometer was estimated to be log(6.9) and log(6.1) copies/mL for FMDV type O and A, respectively. Compared with a commercially available lateral flow assay diagnostic kit for immunochromatographic detection of FMDV type O and A, this dual-modal detection platform offers approximately four-fold greater sensitivity. This highly sensitive and accurate dual-modal detection method can be used for effective disease diagnosis and treatment, and will find application in the early-stage diagnosis of viral diseases and next-generation diagnostic platforms.

We present a novel technology for a cyclo-olefin-copolymer (COC) plastic microfluidic platform for heat control with fully semiconductor process-compatible photolithographic 5 m-wide metal patterns, for heaters, electrodes, and temperature sensors and a thin membrane structure.Through tests of compatibility of some thermoplastic materials with chemical solutions and temperature tolerance to the semiconductor processes (thin film depositions, photolithography, and etchings), we selected COC as a semiconductor process-compatible plastic material for biomedical applications. For photolithography processes, we manufactured the 5' COC wafer with flat surface with c.a. 3 nm surface roughness, employing a novel flame-torched injection-molding method. Furthermore, the part of heating blocks on COC wafers is controlled thickness to the 100 m, to enhance the heat-ramping speeds through reduction of the thermal mass. In order to fabricate the Au thin film micro-patterns for temperature sensors, heaters, and electrodes, Au film (100 nm) was deposited by e-beam evaporator and patterned by using standard photolithography, and wet-etched. The micropatterned Au temperature sensors, heaters, and electrodes was demonstrated For insulating layers, Al 2 O 3 film was deposited by an ALD system, patterned by using the standard photolithography, and wet-etched.Using the COC microfluidic platform, we tested thermal cycling with simple heating and natural cooling on chip with water and, heating rates (5 /s when heating, 3 /s when cooling) are obtained. Therefore, the COC microfluidic platform can be applied to a DNA lab-on-a-chip.

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