Research On Stability Of Continuous Electrophoresis Detection In Microfluidic Chips

Continuous electrophoresis separation of microfluidic chip, representing the born advantages of microfluidic chip such as high speed, high efficiency, low consuming and automation, is one of the most important aspects of microfluidic analysis, and has brilliant application prospects. However in continuous separation, the stability of peak height is poor and the RSD is almost 30% which will strongly affect the analysis of its result.We used the laser-induced fluorescence detector for microfluidic chip based on a confocal biology microscope to study the stability of continuous electrophoresis detection in microfluidic chips. We designed the HV electrode fixer and independently finished the control program of this detector which can display and save the picture,set the parameters and save the results.By analyzing the process of continuous electrophoresis separation, we found that the reason of poor stability is that the sample of next injection was diluted by the buffer entered the sample reservoir during the former separation process. We simulated the flow field of micro-channels in separation, and approved that buffer did enter the sample reservoir and diluted the sample.In order to improve the stability, we designed a new chip by adding a crotch-structure to sample channel of traditional microfluidic chip. By simulating the flow field, we found that this crotch-structure can effectively prevent buffer into sample reservoir and there was no sample leaking. We also optimized the crotch-structure by simulating several different types.Based on above researches, we produced this new crotch-structure microfluidic chip. The silicon mould was made by wet etching, and then by hot-press method the PMMA microfluidic chip was produced. The result of this new chip in LIF detection approved that it can complete the traditional injection and separation. And in continuous separation experiment, the crotch-structure can effectively prevent buffer into sample reservoir and avoid the sample dilution which affects the stability of peak heights. By using this new crotch-structure microfluidic chip, the RSD of peak height in continuous separation can be lowed less than 10% which will greatly improve the stability of continuous electrophoresis separation in microfluidic chips.