Research On DNA Transport Characteristics Based On Solid-state Nanopore Sensor

Solid-state nanopores have potential to be used as sensors which are capable of detecting and analyzing biomolecules and even DNA sequencing.In order to solve the problems of nanopore sequencing,the structure design of micro/nano devices is carried out,the nanopore test platform is set up,the transport properties of ion and DNA molecules in nanopores are studied,and the multi-mode signal parallel Detection and active control of DNA molecule translocation process are achieved.Specific work content and results are as follows:1)The rheological properties of the electrolyte solution in nanometer scale confined space are studied by measuring the I-V curves of nanopores in different concentrations of KC1 solution.It is found that the conductivity of the nanopores at low concentration(? 0.01 mol/L)deviate from the bulk value.It is proposed the conductivity at low concentration is mainly determined by the charge density.At the same time,it is found that the ion mobility in the nanometer channel is different from the bulk value and ion transport is affected by the rectifying effect of the tapered hole.The necessity of effectively reducing the charge density of the wall is proposed.2)The effects of the concentration of salt solution on both sides of the nanopore and the size of the applied bias were studied.It is found the dwelltime(tD)of X.-DNA and the current blockage(IB)become greater with the increase of KCI concentration.However,when the concentration of KCl solution remained constant at the cis side,and the concentration of KCl solution at the trans side was reduced from 1 mol/L to 0.1 mol/L,the relative current blockage(IB/Io)increase by an order of magnitude.In addition,IBbIo and IB produced,when bias voltage is greater,but tD decreases with the bias voltage rise.Therefore,changing the concentration of salt solution or the external bias voltage can effectively reduce the translocation speed of the DNA.And the signal-to-noise ratio can be greatly improved when salt concentration gradients are applied across the nanopore.3)To study the behavior of DNA molecules through nanopores.By comparing the experimental results,it is found that single DNA will be folded or the simultaneous transport of multiple molecules occurs except only in staight state when nanopore diameter is large enough.4)A three-channel parallel detection method of DNA sequencing is proposed,in which ion current,the force signal of AFM probe and tunneling current signal based on field effect transistor are detected simultaneously.It makes the diversity of detection realized.The first two kinds of signals are tested tentatively,which proves that the parallel detection method is feasible and successfully realizes the active control of DNA molecule translocation event.The translocation speed of DNA molecules is controlled at much less than 1base/ms,which has been able to fully meet the needs of sequencing.5)A method for studying the resistance of nanopores has been developed.The resistance of the nanopores can be studied by detecting the regular current blockage signal caused by AFM probe scanning near the nanopore.By analyzing the experimental results,it is found that the range of ion current changes in the probe is very consistent with the capture radius,which will be beneficial to study how the moving DNA molecules affect the pore resistance of nanopore.