The Structural And Control Circuit Design Of Real-time Polymerase Chain Reaction On A Microchip

Polymerase chain reaction (PCR) has been a popular technique for DNA amplification which is a kind of DNA amplification technique outside the body. Amplification of nucleic acids is essential for many biological applications. A single DNA molecule can be copied a billion times to allow easy detection. PCR microchips are potentially low cost, disposable and possible for handheld instruments to be manufactured. Owing to the progressive development of PCR over the last two decades, it has become a central technique for nucleic acid analysis and is the most widely used method for DNA amplification in Laboratory.Combining the research fruit of the domestic and overseas, this paper studies the realization of the PCR on a microchip.First we introduced the process denaturation, annealing and extension of PCR and biochemical reaction steps, and then developed a simple polymeric PCR microchip. In the PCR microchip, we integrated a micro ectromagnetic pump, improved the staggered herringbone mixer which was designed by Stroock. At last, we adopted microheater and fluorescence detection micro apparatus department.The main research topic of the paper is designing a suitable microvalve for PCR. Currently the microvalves used in PCR were common valves which were not meeting the requirements of PCR, such as high sealing. So we designed a microvalve which specifical for PCR. The microvalve, with the stub and stem components, was positioned directly above the plate with drilled holes identical to stem. The motor provided the force necessary to actuate the valve. It incorporated in the integrated chip conceptually utilizes an airtight plugging mechanism to prevent fluid loss from open-to-ambient drilled access holes on the upper substrate of the chip. In addition to the snug fit, application of thrust above the stub of the microvalve will also ensure a tight seal inside the access holes. At last, we designed thermal-structural analysis for the microvalve using ANSYS 11.0 and concluded that the microvalve was more suitable than passive plug microvalve. The hardware control circuit and software control design are introduced according to the characteristics of the PCR microchip. In the hardware design, we used AT89C51 as the center controlling part. A kind of PWM power used in micropump and valve were designed. In the software design, we introduced the timing of the PCR control systerm and using Microsoft Communication Control designed the PC interface, which was provided by VC++6.0. Finally, we simulated the designing control system by Protues. Experiment results show that the control system satisfied the design request of micropump and valve, and the largest measurement error of temperature controlε≤0.05℃.