Research On A Micro Label-free Static PCR System

Traditional PCR systems are limited by long reaction time, low power efficiency and high sample consumption.In order to solve these problems, MEMS technology and thermal transfer theory was used to design,fabricate and test a label-free micro static PCR system for its high surface-volume ratio and low capacity.This system is consisting of three important modules:the micro heater, the micro electrodes and the micro reservoir, which are based silicon substrate MEMS technology, label-free electrochemical test technology and polymer seal technology.They are to be discussed as follows:Firstly, this paper focused on the research of silicon-based micro heater. A thermal transfer model was set up according to Fourier's Law.The relationship between substrate and thermal property was studied.The key thermal coefficients are acquired through experiments. As Biot number is less than 0.1,it was reasonable to employ lumped capacity solution.By FEA and calculation,the air gap's at 200μm was best for improving efficiency.Through CMOS-compatible process,the silicon based micro heater was fabricated and control tests based on user-defined voltage wave were carried out.Control experiment results indicated the temperature precision was±1.5℃,which was within the PCR reaction limit.Secondly, this paper focused on the research of label-free electrochemical micro electrodes.The micro electrodes were designed through finite element analysis method for smooth electrical field distribution.According to bio-compatible and electrochemical requirements, the work electrode was designed as 100nm Pt, reference electrode as 1 OOnm Al and counter electrode as 100nm Ag. And they were fabricated through metal deposition and lift-off process.By electrochemical methods, the label-free electrodes can detect a water solution of methanol,ethanol and formaldehyde.Their peak voltages are-0.25V,0.15V and 0.37V,respectively. One experiment was also carried out to enhance the micro electrode signal through deposition of gold nano particles.Thirdly, this paper also focused on the research of polymer micro reservoir. The micro reservoir was designed with hydrophilic SU8 and hydrophobic PDMS with their contact angles measured,and fabricated through polymer process.In order to monitor the micro volume changes in the reservoir, an untouchable indirect measurement method was discussed. Experiments results show at room temperature the solution kept unchanged for 500s and left 30% volume for 300s under 95℃.At last, the micro static PCR system was tested by amplifying DsRedDNA for designed cycles.The micro electrode results were identical to gel electrophoresis results.