The Application Of Microfluidic Technique To Study The Flow Properties Of Single-stranded DNAs

Most of the processes in DNA-based in vitro genetic manipulation or in vivo transcription are established on transformation between their single-strands(ssDNA) and double-strands(dsDNA), in which there assumes that the basic mechanical properties of DNA not only dsDNA but ssDNA play important roles. Recently there are a lot of literatures revealing out some interesting mechanical behaviors of dsDNA, however, little is known on that of ssDNA. This thesis is attempt to investigation what flow property and behavior are emerging on ssDNAs with different length or even different sequences when they flow in microchannels.To attain the above aim, this paper has done three steps work. Firstly, 30μm-diameter inner and 5mm efficient-length microchannel array in PDMS was constructed using micro-molding, one of conventional techniques of soft lithography. The nature of hydrophilic and hydrophobic on the inner wall of the microchannels were considered during the above fabrication.Next, the microflow experiment set for carrying out micro-PIV study was established based on the thus PDMS microchannels, combining Leica DMI4000B fluorescence microscopy, Lightning RDT? high speed camera, and Longer TS2-60 inject pump. Based on this set, the flow behavior and properties of ssDNA (oligonucleotides) were tested and preliminary analyzed.Then, the flow properties of several typical oligonucleotide solution in hydrophilic microchannels were investigated. The primary efforts are focused on their velocity distributing and viscosity, which are two parameters for facilitating to make a preliminary evaluation of the microflow properties of the oligonucleotides solutions. Based on the two parameters, the relationships among the solution viscosity, the length of oligonucleotide, the concentration of oligonucleotide solution, and temperature were analyzed. The data shown that the microflow nature of oligonucleotide solution was laminar in such round microchannel; the viscosity of low molecular weight oligonucleotide solution could be calculated by applying Poiseuille formula; and that the temperature and the concentration of the oligonucleotide solutions exerted great influence on their change of viscosity, some of which, appeared as the dependence on the sequence length, especially under the same pressure.These above primary results would have foundamental meaning for deep analysis of DNA hybridization dynamics under microflow.