The Theory And Technology Of Ion And DNA Molecule Tansport In Nanopores

Nanopore-based 2D membrane separation and single molecule detection are widely used in personalized medicine,new energy,genetic engineering and environmental engineering,which are closely related to the future of human beings.With the development of micro/nano manufacturing,reducing the size of nanopore can not only improve the performance of nanopore related devices,but also provide an effective way to study the behavior of ions and single molecule at the nanoscale.In this paper,the basic theory of ion and DNA molecular transport in nanopores has been gradually established,including the theoretical system of ion transport from continuum to semi-continuum and then to many-body,and the molecular translocation theory with the interaction of field force(including electric field and flow field)and random force.The key technologies in nanopore field have been studied and developed,including nanopore fabricating and testing technology,high-purity ion separation technology and DNA detection and control technology,which enhanced the independent intellectual property rights and core competitiveness in the micro/nano manufacturing industry.For the basic theory,(1)the classical continuum transport theoretical model is improved,the application scope of classical hydrodynamics is explored and experimentally defined,the main factors affecting the local potential around the nanopore are proposed,and the ion concentration in the electric double layer with the ionization equilibrium reaction is solved,which lays a solid foundation for the subsequent establishment of many-body transport theory.(2)A theoretical system of many-body transport was established.The complex system of solute-solvent and solute-solute direct interaction is investigated by molecular dynamics simulations.The internal mechanism of ionic hydration layer destruction,mobility reduction and the ion selectivity is revealed.(3)In order to further explore the surface effects on ion transport in the nanoscale confined space,including the permittivity constant reduction,viscosity increase,electric field enhancement,charge inversion and surface capture,the systematic research on the behaviors of ions,water molecules and biomolecules in the solid-liquid interface has been carried out.(4)The biomolecule translocation theory in the nano-confined space is completed,considering the diffusion(thermal)movement,the capturing dynamic process and conformation after entering the nanopore,which provides the basic physical parameters for the design and large-scale manufacturing of single molecule detection devices.For key technologies,(1)the nanopore fabrication and testing are completed.The low-cost,fast and high-precision fabrication of nanopores is realized by exploring the dielectric breakdown method.A series of nanopores with diameter from 1.8 nm to 26 nm are fabricated by high-energy beam.Through the measurement of ionic conductance in the whole concentration spectrum,it is found that the critical point for the continuum transport theory to gradually fail in the nanopore with a diameter of less than 4.5 nm.Through further measurement of different electrolyte solutions such as Na Cl,KI,Li I,HCl and KF,it is revealed that the formation of ion pair is an important mechanism for the drastically decline of ion mobility in the small nanopore.(2)An ion selective membrane with high selectivity and permeability designed.Through density functional theory(DFT)calculation,it is found that a uniform pore array with uniform size and shape appeared in the dense electronic cloud of stretched graphene,so as to obtain the maximum possible pore density under the minimum film thickness.Molecular dynamics(MD)simulation is used to systematically study the permeation process and selectivity mechanism of Li~+,Na~+and K~+with different membrane charge density.According to the simulation parameters,the graphene ion sieve with adjustable strain and surface charge is designed,which can realize the membrane separation system with low energy consumption and high productivity,and a series of design criteria for the future development of 2D membrane separation technology are proposed.(3)The detection and manipulation of biomolecules are realized.λ-DNA and 20 kbp DNA are detected by solid-state nanopores.In order to simplify translocation of biomolecules and find out the general rule,the ECD(event charge deficit)distribution of translocation events is analyzed.The reverse flow field is applied to control the DNA and reduce the translocation velocity,so as to improve the signal captured by patch clamp,which is a simple and effective control method for biomolecule detection and research.