Design And Fabrication Of Magnetic Tweezers System Based On Nanopore Sequencing

The fourth generation technology of DNA sequencing based on nanopore which is most likely to realize the diagnosis and treatment of conventional gene disease at present.The nanopore chip is the key device for experiment of DNA sequencing,is sensor converts information of place of DNA molecule to ion currents signal;and magnetic tweezers is an effective tool to control and simplify the complex behavior of DNA when it’s in nanopore.The main work done by the paper as follow:（1）A new structure of nanopore chip for solid state nanopore sequencing technology based on kinetic proofreading is designed.In addition to sandwich structure layers of Si₃N₄/SiO₂/Si₃N₄,increase the double sacrifice layers of SiO₂/Si₃N₄ while reducing the stress of the free-standing film can also reduce the noise by increasing the capacitance.The thickness of the films is determined by thermal stress to avoid cracking of the film during the production process.The process for fabrication sandwich structure film using NEMS was designed,including low-pressure vapor deposition,lithography,reactive ion beam etching and wet etching and so on.To gain high quality free-standing sandwich structure film.The film fabrication in this paper is further etched by focused ion beam（FIB）,a nanopore of about 5 nm in diameter was made by Zeiss’ s helium ion microscope.（2）A system of dual side magnetic tweezers for stretching DNA by two sides was designed and build.The magnetic tweezers based on a dual-side probe station,including magnetic circuit system,magnetic needle manipulator,microscopic imaging system,sample liquid pool,faraday cage and so on.Experiments were conducted on single and double pole controlled magnetic beads.Magnetic tweezers system can complete the manual adjustment of micromanipulator to control a single magnetic bead within a distance of 10μm,and achieved the control chain from centimeter → millimeter → micrometer → nanometer;ANSYS was used to simulate the magnetic field and explain the behavior of magnetic beads in solution.And DNA sequencing experiment was performed with magnetic tweezers.The ion current signal to understand the effect caused by magnetic tweezers was analysed.