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Development of a Miniature Permanent Magnetic Circuit for Nuclear Magnetic Resonance Chip

Chinese Journal of Mechanical Engineering 2013年第4期26卷 689-694页

作者： LU Rongsheng YI Hong WU Weiping NI Zhonghua jiangsu key laboratory for design and manufacture of micro-nano biomedical instruments Southeast University

The existing researches of miniature magnetic circuits focus on the single-sided permanent magnetic circuits and the Halbach permanent magnetic circuits. In the single-sided permanent magnetic circuits, the magnetic flux density is always very low in the work region. In the Halbach permanent magnetic circuits, there are always great difficulties in the manufacturing and assembly process. The static magnetic flux density required for nuclear magnetic resonance(NMR) chip is analyzed based on the signal noise ratio(SNR) calculation model, and then a miniature C-shaped permanent magnetic circuit is designed as the required magnetic flux density. Based on Kirchhoff’s law and magnetic flux refraction principle, the concept of a single shimming ring is proposed to improve the performance of the designed magnetic circuit. Using the finite element method, a comparative calculation is conducted. The calculation results demonstrate that the magnetic circuit improved with a single shimming has higher magnetic flux density and better magnetic field homogeneity than the one improved with no shimming ring or double shimming rings. The proposed magnetic circuit is manufactured and its experimental test platform is also built. The magnetic flux density measured in the work region is 0.7 T, which is well coincided with the theoretical design. The spatial variation of the magnetic field is within the range of the instrument error. At last, the temperature dependence of the magnetic flux density produced by the proposed magnetic circuit is investigated through both theoretical analysis and experimental study, and a linear functional model is obtained. The proposed research is crucial for solving the problem in the application of NMR-chip under different environmental temperatures.

关键词： nuclear magnetic resonance microfluidic chip permanent magnet magnetic flux density

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Integrated solid-state nanopore devices for third generation DNA sequencing

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Science China(Technological Sciences) 2014年第10期57卷 1925-1935页

作者： WU GenSheng ZHANG Yin SI Wei SHA JingJie LIU Lei CHEN YunFei jiangsu key laboratory for design and manufacture of micro-nano biomedical instruments Southeast University

Third generation DNA sequencing relies on monitoring the ionic current blockage during the DNA molecule’s threading through a nanoscale *** is still really tough to attain the single base discrimination on a DNA strand by merely analyzing the ionic current due to speedy DNA translocation and low spatial *** integrated configurations are pursued to present versatile comparative dissimilarities of the four bases by enhancing the spatial resolution within a DNA molecule translocation event,such as transverse tunneling current,local potential change,and capacitance oriented voltage *** this mini review,the insight is provided into the status quo on several functionalized techniques and methodologies for DNA sequencing and furthermore concluding remark and outlook are presented.

关键词： DNA sequencing solid-state nanopore spatial resolution integrated sensors

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Ion and water transport in charge-modified graphene nanopores

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Chinese Physics B 2015年第10期24卷 553-558页

作者：裘英华李堃陈伟宇司伟谭启檐陈云飞 School of Mechanical Engineering and jiangsu key laboratory for design and manufacture of micro-nano biomedical instruments Southeast University

Porous graphene has a high mechanical strength and an atomic-layer thickness that makes it a promising material for material separation and biomolecule sensing. Electrostatic interactions between charges in aqueous solutions are a type of strong long-range interaction that may greatly influence fluid transport through nanopores. In this study, molecular dynamic simulations were conducted to investigate ion and water transport through 1.05-nm diameter monolayer graphene nanopores, with their edges charge-modified. Our results indicated that these nanopores are selective to counterions when they are charged. As the charge amount increases, the total ionic currents show an increase-decrease profile while the coion currents monotonically decrease. The co-ion rejection can reach 76.5% and 90.2% when the nanopores are negatively and positively charged, respectively. The Cl-ion current increases and reaches a plateau, and the Na＋current decreases as the charge amount increases in systems in which Na＋ions act as counterions. In addition, charge modification can enhance water transport through nanopores. This is mainly due to the ion selectivity of the nanopores. Notably, positive charges on the pore edges facilitate water transport much more strongly than negative charges.

关键词： monolayer porous graphene charge-modified nanopore ion selectivity ionic current water trans-port

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Multi-relaxation time lattice Boltzmann simulation of inertial secondary flow in a curved microchannel

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Chinese Physics B 2013年第11期22卷 376-384页

作者：孙东科项楠姜迪陈科易红倪中华 jiangsu key laboratory for design and manufacture of micro-nano biomedical instruments School of Mechanical Engineering Southeast University

The inertial secondary flow is particularly important tbr hydrodynamic lbcusing and particle manipulation m biomed- ical research. In this paper, the development of the inertial secondary flow structure in a curved microchannel was investi- gated by the multi relaxation time lattice Boltzmann equation model with a force term. The numerical results indicate that the viscous and inertial competition dominates the development of secondary flow structure development. The Reynolds number, Dean number, and the cross section aspect ratio influence significantly on the development of the secondary vor- texes. Both the intensity of secondary flow and the distance between the normalized vortex centers are functions of Dean numbers but independent of channel curvature radius. In addition, the competition mechanism between the viscous and inertial effects were discussed by performing the particle focusing experiments. The present investigation provides an improved understanding of the development of inertial secondary flows in curved microchannels.

关键词： lattice Boltzmann method multi relaxation time microchannel inertial secondary flow

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Temperature effect on translocation speed and capture rate of nanopore-based DNA detection

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Science China(Technological Sciences) 2015年第3期58卷 519-525页

作者： ZHANGYin WU GenSheng MA Jian YUAN ZhiShan SI Wei LIU Lei SHA JingJie CHEN YunFei jiangsu key laboratory for design and manufacture of micro-nano biomedical instruments School of Mechanical Engineering Southeast University

We study the effects of electrolyte temperature on DNA molecule translocation experimentally without and with a temperature gradient across nanopore *** same temperatures on both electrolyte chambers are first *** DNA molecule translocation time is measured to be 2.44 ms at 2°C in both chambers,which is 1.57 times longer than at 20°*** the temperature difference effect is characterized in both *** results show that the DNA translocation speed can be slowed down as long as one side temperature is lowered,irrespective of the temperature gradient *** indicates that the thermophoretic driving force generated by a temperature gradient has no obvious effect on the threading speed of DNA molecules,while the main reason for the slowed DNA translocation speed is the increased ***,the capture rate of DNA molecules is enhanced under a temperature gradient condition,and the capture rate during DNA translocation from hot side at 21°C to cold one at 2°C is 1.7 times larger than that under the condition of both chambers at 20°***,an optimized configuration is proposed to acquire higher capture rates and lower DNA translocation speeds.

关键词： nanopore DNA detection temperature translocation speed capture rate

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Effect of nanopore size on poly(dT)_(30) translocation through silicon nitride membrane

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Science China(Technological Sciences) 2013年第10期56卷 2398-2402页

作者： SI Wei SHA JingJie LIU Lei QIU YingHua CHEN YunFei jiangsu key laboratory for design and manufacture of micro-nano biomedical instruments Southeast University

The nanopore size effect on translocation of poly(dT)30through Si3N4 membrane is *** this paper,we report that the speed of the poly(dT)30 transport through Si3N4 nanopores can be slowed down by half through increasing the nanopore diameter from 4.8 nm to 10.8 *** results are consistent with our simulation ***,the current blockage induced by DNA passing through the nanopore is less obvious as pore diameter is larger,which is in good agreement with the theoretical *** conclusion about DNA transport through nanopores is beneficial for the design of DNA sequencing devices.

关键词： solid-state nanopore nanopore technology single molecule sensor molecular dynamics simulation slow down

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Experimental study on filtering,transporting, concentrating and focusing of microparticles based on optically induced dielectrophoresis

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Science China(Technological Sciences) 2010年第9期53卷 2388-2396页

作者： ZHU XiaoLu,YIN ZhiFeng,GAO ZhiQiang & NI ZhongHua jiangsu key laboratory for design and manufacture of micro-nano biomedical instruments,Southeast University,Nanjing 211189,China jiangsu key laboratory for design and manufacture of micro-nano biomedical instruments Southeast University Nanjing China

The key problem to be solved for the dielectrophoresis (DEP) application is to provide dynamically reconfigurable microelectrodes and low-cost methodology for bioparticle *** emergence of optically induced DEP (ODEP) based on photoconductive effect provides a potential solution for the above *** this paper,an ODEP chip is designed and fabricated,and the corresponding experimental platform was established,whereupon four types of particle manipulation regimes–filtering,transporting,concentrating and focusing based on ODEP are experimentally demonstrated and the operating performances are quantitatively *** experiment results show that the functions and performances of ODEP manipulation are heavily dependent on the geometrical shape,scales and speed of optical patterns,actuating signal frequency and the electric conductivity of the *** manipulation efficiency can increase by more than 50% via increasing the optical line ***,the efficiency is obviously affected by the inclination angle of the optical oblique lines in the manipulation of particle ***,the maximum velocity of particles increases with the increment of the inside radius and the thickness of the optical trapping *** manipulation efficiency is always related to signal frequency and solution conductivity,and empirically,satisfactory performance and high efficiency are obtained when the solution electric conductivity ranges from 5×10-4 S/m to 5×10-3 S/m.

关键词： optically-induced dielectrophoresis particle manipulation filtering transporting concentrating focusing

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DNA sequencing technology based on nanopore sensors by theoretical calculations and simulations

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Chinese Science Bulletin 2014年第35期59卷 4929-4941页

作者： Wei Si Yin Zhang Gensheng Wu Jingjie Sha Lei Liu Yunfei Chen jiangsu key laboratory for design and manufacture of micro-nano biomedical instruments Southeast University

DNA sequencing based on nanopore sensors is a promising tool for third-generation sequencing technology because of its special properties,such as revolutionized speed and low *** about two decades of nanopore technology development,the pioneering work has demonstrated the ability of nanopores to perform single-molecule detection and DNA ***,the microscopic mechanisms of DNA transport dynamics through nanopores remain largely ***,DNA microscopic transport in a nanopore is difficult to characterize and several unexpected experimental observations are *** limitation can be resolved using theoretical calculations and *** computational methods can monitor the entire dynamic process that DNA undergoes in solution at a single-atom resolution that can accurately unveil the mystery of DNA transport dynamics and predict certain unexpected *** paper mainly reports the recent applications of computational and simulation methods applied to the study of DNA transport through both biological and synthetic *** hope the theoretical calculations and simulations of DNA transport through nanopores can benefit the design of DNA sequencing devices.

关键词： DNA测序技术可计算性纳米孔传感器模拟应用程序原子分辨率微观机制

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Glass capillary nanopore for single molecule detection

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Science China(Technological Sciences) 2015年第5期58卷 803-812页

作者： SHA JingJie SI Wei XU Wei ZOU YiRen CHEN YunFei jiangsu key laboratory for design and manufacture of micro-nano biomedical instruments Southeast University School of Mechanical Engineering Southeast University

Single molecule detection based on nanopore technology is a very promising approach for medical diagnostics, drug therapy and even DNA sequencing. Compared with other biological nanopores and solid-state nanopores, the glass capillary nanopore has low cost, easy availability and stable mechanical characteristics, thus it has been widely used in the nanopore technology for single molecule detection. In this review, we will focus on the studies of the glass nanopore sensors. The popular glass nanopore fabrication methods would be introduced, and the applications of glass nanopores in the detection of nanoparticles, proteins and DNA molecules would be presented. We hope this review will help widen field of vision and promote the development of the nanopore technology based on the glass capillary nanopores.

关键词： fabrication capillary nanotubes sequencing diameters SWNTs DNA etching diagnostics nanometer

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OPTIMIZATION OF CORONARY STENT STRUCTURE design FOR MAXIMIZING THE ANTICOMPRESSION MECHANICAL PROPERTY

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Chinese Journal of Mechanical Engineering 2008年第6期21卷 98-102页

作者： SHEN Xiang YI Hong NI Zhonghua GU Xingzhong jiangsu Province key laboratory for design and manufacture of micro-nano biomedical instruments Southeast University Nanjing 211189 China

Excellent mechanical property of the anti-compression or high collapse pressure has become an essential feature of new coronary stents. How to determine the design parameters of stent becomes the key to improve the stent quality. An integrated approach using radial basis function neural network （RBFNN） and genetic algorithm （GA） for the optimization of anti-compression mechanical property of stent is presented in this paper. First, finite element simulation and RBFNN are used to map the complex non-linear relationship between the collapse pressure and stent design parameters. Then GA is employed with the fitness function based on an RBFNN model for arriving at optimum configuration of the stent by maximizing the collapse pressure. The results of numerical experiment demonstrate that the combination of RBFNN and GA is an effective approach for the mechanical properties optimization of stent.

关键词： Stent Anti-compression Genetic algorithm (GA) Radial basis function neural network Optimization

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