The Study Of The Reversal Movement Of The ?-DNA Molecules Through The Microchannel With The Fluorescence Imaging Technique

At present, the research on biological molecules with the micro/nanofluidic technique is one of the hotspot. The dynamic characteristic of the biological molecules is the foundation of biochip technique and biological sensor. In this paper, with the fluorescence imaging technique, the movement of DNA molecules through microchannel under different electric field intensity was studied, and analyzed the influence of the space limitation (the channel size) and the electric field intensity carefully on the movement of DNA molecules. The experimental investigations are summarized below:(1) The factors that influence the DNA molecules into the microchannel smoothly were studied. The experiment is optimized from the material of the electrode and the surface properties of the microchannel. A large number of experiments show that, compared to the copper electrode, the platinum electrode is more conducive to inducing the DNA molecules through the microchannel. By improving the hydrophilicity of the surface of microchannel with PLL-g-PEG solution, the DNA molecules have higher chance to enter and move through the channel. The improved hydrophilicity of the microchannel can also reduce the influence of the electroosmotic flow on the movement of the DNA molecule in the microchannel. It causes the observation of the DNA molecule easier.(2) The DNA molecules moving in different space constraint was studied. The DNA molecules within buffer solutions of different concentrations were observed on the silica surface. The result shows that to get the best dispersion of DNA molecule in the solution, the optimal solution concentration is 10 mM. The DNA molecular movement in microchannels with different inner diameters (300 ?m,10 ?m,5 ?m) was studied. The smaller the inner diameter, the clearer moving direction of the DNA molecules. The DNA molecules moving in the channel of 10/5 ?m were studied in deeply. It is found that the smaller the channel inner diameter, the higher the threshold electric field intensity is required for the DNA molecular reversal movement to be realized.(3) The effect of electric field intensity on the movement of DNA molecules in the microchannel was studied. The experiments show that the direction of the DNA molecules is inconformity under the different electric field intensity. The threshold electric field intensities related to the reversal movement of DNA molecule are 4.0×103 V/m and 5.3×103 V/m in the microchannel of 10 and 5 ?m diameter. When the electric field intensity smaller than the threshold electric field intensity, the moving direction of the DNA molecule was consistent with that of the electric field. When the electric field intensity large than the threshold electric field intensity, the movement direction of the DNA molecules was opposite direction to the electric field. The electric field intensity variations of velocity and acceleration of the DNA molecules were analyzed. It is found that the acceleration of DNA molecule driven at the threshold electric field intensity is larger than that at other electric field intensities. The reversal phenomenon and the movement regulation of the DNA molecules under the electric field intensity were analyzed by the competition of the electrophoresis and the electroosmotic flow. The velocity of the fluid and DNA molecules were calculated by the self-developed procedure with MATLAB.The dynamic characteristic of the DNA molecules through the microchannel is studied in the paper, and the founds are meaningful on precisely designing electrokinetic based biochips to achieve manipulation and separation of DNA molecules.