A micro circulating PCR chip using a suction-type membrane for fluidic transport
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A new micromachined circulating polymerase chain reaction (PCR) chip is reported in this study. A novel liquid transportation mechanism utilizing a suction-type membrane and three microvalves were used to create a new microfluidic control module to rapidly transport the DNA samples and PCR reagents around three bio-reactors operating at three different temperatures. When operating at a membrane actuation frequency of 14.29 Hz and a pressure of 5 psi, the sample flow rate in the microfluidic control module can be as high as 18 μL/s. In addition, an array-type microheater was adopted to improve the temperature uniformity in the reaction chambers. Open-type reaction chambers were designed to facilitate temperature calibration. Experimental data from infrared images showed that the percentage of area inside the reaction chamber with a thermal variation of less than 1°C was over 90% for a denaturing temperature of 94°C. Three array-type heaters and temperature sensors were integrated into this new circulating PCR chip to modulate three specific operating temperatures for the denaturing, annealing, and extension steps of a PCR process. With this approach, the cycle numbers and reaction times of the three separate reaction steps can be individually adjusted. To verify the performance of this circulating PCR chip, a PCR process to amplify a detection gene (150 base pairs) associated with the hepatitis C virus was performed. Experimental results showed that DNA samples with concentrations ranging from 105 to 102copies/μL can be successfully amplified. Therefore, this new circulating PCR chip may provide a useful platform for genetic identification and molecular diagnosis.
KeywordsPCR Molecular diagnosis Microfluidics Microheaters MEMS
Gold Bio-MEMS Bio-micro-electro-mechanical-systems
Hepatitis C virus
Polymerase chain reaction
Scanning electron microscope
The authors gratefully acknowledge the financial supports provided by the National Science Council of Taiwan NSC 96-2622-E-002-001 and NSC 96-2120-M-006-008 for this study.
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