Development of a DNA-extraction and Polymerase-chain-reaction Microchip by using Magnetic Beads and Thermo-pneumatic Valves
Date Issued
2009
Date
2009
Author(s)
Yang, Xin-Ying
Abstract
In this work, we develop a DNA extraction and polymerase chain reaction (PCR) microchip utilizing magnetic beads driven by electromagnetic force. The size of the self-contained system, which comprises a microfluidic chip, micro-heaters, micro-temperature sensors, coils, a piezoelectric-plate and a control module, is 72mm × 53.5mm × 11mm. The parameters such as cycle times, cycle numbers and reaction temperatures can be adjusted and controlled by a microcontroller. The device can fully operates with a 12V DC voltage, and does not require any external pumping equipment or bulky power supply.he microfluidic chip is composed of three layers, a PDMS microchannel layer, a PDMS air chamber membrane, and a glass cover. A sample loading chamber, a wash buffer chamber, an elution buffer chamber and a PCR chamber are fabricated on the microfluidic chip. A linear array of coils, which is located underneath the microfluidic chip, is also implemented in the system. The coil array is in charge of manipulating magnetic beads, on which DNA are attached, through the microchannel and and chambers. Since all solutions for DNA extraction and PCR are loaded in different chambers prior to the operation, thermo-pneumatic microvalves, which are integrated in the microfluidic chip, are used to isolate those solutions. Besides, an integrated thermo-pneumatic micropump is used to actuate DNA solution into the PCR chamber. Both microvalves and micropump in the system perform well with a very mild temperature elevation. In the PCR chamber, heaters and temperature sensors fabricated by MEMS techniques were implemented, and the PID scheme are employed to control the temperature to desired level with desired durations. ransient temperature of the PCR chamber is measured by an infrared thermometer. An infrared thermal imager is used to observed temperature distribution in the PCR chamber and near the thermo-pneumatic microvalves. Concentration of the DNA extracted from blood is detected by a UV-visible spectrophotometer. Slab gel electrophoresis experiments are carried out to demonstrate the PCR results. The proposed system only needs 10μL PCR liquid sample and takes less than 74 minutes for a whole PCR process.
Subjects
DNA extraction
PCR
biochip
MEMS
Type
thesis
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