The Electrodynamic Characteristics Of ?-DNA Molecule Moving In And Out A Micron Channel Port Studied With The Single Molecular Fluorescence Imaging Technique

In this paper,the microfluidic technology and inverted fluorescence microscopy are combined to observe and study the details of a single DNA molecule passing through the microchannel under the action of electric field force in real time.Under the condition of applied electric field,the conformation and motion state of DNA molecules will be diverse when they cross the micro-nano channel.Due to the unclear dynamic mechanism of DNA molecules in the microchannel port,correct measures cannot be taken,resulting in DNA molecules unable to enter the microchannel port due to entanglement or other influences,or unable to enter the micron channel and other problems.In this paper,the relationship between the electrodynamic characteristics of DNA molecules and the intensity of applied electric field and the inner diameter of the microchannel is studied.The study of the electrodynamic characteristics of DNA molecules in micro-nano channels is of great theoretical significance for the design of micro-nano fluidic devices and biosensors.Mainly include the following:(1)In the 50 ?m channel,the threshold electric field intensity that DNA can enter the microchannel from the negative port and the electric field intensity range that DNA molecules can smoothly pass through the microchannel are studied.When the applied electric field strength E<2.5×103 V/m,the DNA molecules close to the negative port cannot enter,when the applied electric field strength E=2.5×103 V/m,the DNA molecules can just enter the negative port,So the threshold electric field intensity E=2.5×103 V/m that DNA molecules can enter from the negative port of the 50 ?m channel.The range of electric field strength for DNA molecules to smoothly pass through the microchannel is 2.5×103V/m ? E ?7.5×103 V/m.(2)Under the condition of changing the intensity of the applied electric field,DNA molecules can be guided to enter different areas when flowing out of the 50 ?m microchannel port,which realizes the flexible manipulation of DNA molecules.The relationship between the movement and distribution of DNA molecules at the port of the microchannel and the intensity of the applied electric field is studied.When the applied electric field strength is constant,the DNA starts to deflect within the range of 1-2 times the tube diameter from the outlet port,and the radial Suffman force of the DNA at the central axis and the tube wall is almost zero,and no deflection occurs.With the increase of the applied electric field intensity,the radial Suffman force of the DNA at the positive port increases;the microchannel port due to the competition of electroosmotic flow and electrophoresis speed causes the DNA to reverse movement,and the inversion threshold electric field intensity E=7.5×103 V/m,DNA inversion gradually moves away from the positive port as the electric field strength increases;when the electric field strength E>9.375×103 V/m,DNA reciprocates at the negative port,and As the electric field strength increases,the frequency of the reciprocating movement of the DNA molecules increases.(3)The influence of the inner diameter of the microchannel on the speed and conformation of DNA in the microchannel was studied.When the applied electric field is the same,the smaller the inner diameter of the microchannel,the greater the speed of DNA migration in the channel,and the more obvious the stretching effect.When the inner diameter of the microchannel is equal to 5 ?m,all DNA molecules in the channel can be reversed.