Dielectrophoresis （DEP） is one of the most popular techniques for bio-particle manipulation in microfluidic systems. Traditional calculation of dielectrophoretic forces of single particle based on the approximation ...Dielectrophoresis （DEP） is one of the most popular techniques for bio-particle manipulation in microfluidic systems. Traditional calculation of dielectrophoretic forces of single particle based on the approximation of equivalent dipole moment （EDM） cannot be directly applied on the dense particle interactions in an electrical field. The Maxwell stress tensor （MST） method is strictly accurate in the theory for dielectrophoretic forces of particle interaction, but the cumbersome and complicated numerical computation greatly limits its practical applications. A novel iterative dipole moment （IDM） method is pre- sented in this work for calculating the dielectrophoretic forces of particle-particle inter- actions. The accuracy, convergence, and simplicity of the IDM are confirmed by a series of examples of two-particle interaction in a DC/AC electrical field. The results indicate that the IDM is able to calculate the DEP particle interaction forces in good agreement with the MST method. The IDM is a purely analytical operation and does not require complicated numerical computation for solving the differential equations of an electrical field while the particle is moving.展开更多
In this study, the irreversible deposition of microparticles from electrokinetic microfluidic flow in a 90° bend was exami- ned both computationally and theoretically. The flow and electric fields were firstly si...In this study, the irreversible deposition of microparticles from electrokinetic microfluidic flow in a 90° bend was exami- ned both computationally and theoretically. The flow and electric fields were firstly simulated by the finite volume method, and then a large number of microparticles were injected and traced by the one-way coupling Lagrangian model, incorporating the electrical, hydrodynamic and near-wall repulsive forces exerted on the microparticles. The simulation results indicate that the microparticles with larger size are repelled to close to the upper region of the outer wall under the effect of dielectrophoresis （DEP） force, and the near-wall repulsive force which prevented particles from colliding with the wall would decrease the particles＇ ultimate deposition efficiency. In addition, the specified exponential relationship between the particle deposition efficiency and its relaxation time or par- ticle Stokes number are theoretically derived when the near-wall repulsive force is considered or not.展开更多
<正> In this paper, we have utilized the principle of dielectrophoresis to determine the dielectrophoretic spectra of single levitated tobacco leaf protoplast at various suspending media conductivities (12.5 μS...<正> In this paper, we have utilized the principle of dielectrophoresis to determine the dielectrophoretic spectra of single levitated tobacco leaf protoplast at various suspending media conductivities (12.5 μS/cm-520 μS/cm) over wide frequencies (10 Hz—15 MHz). From the experimental data, the membrane capacitance of the single protoplast which was 0.40±0.03μF/cm^2 has been obtained and the dipole interaction of two protoplasts in electrofusion has also been analysed. When the external electric field E_c=1.5kV/cm was applied and the frequency was higher than 20 kHz, the dipole interaction pressure ~πd would be much larger than the membrane potential pressure ~πm, and the pressure ~πd could be the main reason for membraue pores. This conclusion will provide a new basis to improve the protocol of cell electrofusion.展开更多
This paper presents a high-efficiency technique based on dielectrophoresis (DEP) for assembling metal, semiconductor, and polymer nanorods, which are synthesized by electrochemical deposition (ECD). The assembly patte...This paper presents a high-efficiency technique based on dielectrophoresis (DEP) for assembling metal, semiconductor, and polymer nanorods, which are synthesized by electrochemical deposition (ECD). The assembly patterns of these nanorods (width: 20 nm; length: 7 μm) were designed using a finite element method (FEM) simulation tool. Further, these nanorods were used in our experiment after their assembly patterns were fabricated. The assembly yield was found to be approximately 70% at an AC voltage of 30 Vp-p and at frequencies of 20 and 30 kHz, and the DC voltage prevented the random alignment of the nanorods at the edge of the assembly pattern. Moreover, the above-mentioned nanorods, which had different permittivities, were found to have similar assembly yields. The proposed method can be improved and applied to nanostructure device fabrication.展开更多
This numerical study proposes a cell sorting technique based on dielectrophoresis(DEP)in a microfluidic chip.Under the joint effect of DEP and fluid drag,white blood cells and circulating tumor cells are separated be...This numerical study proposes a cell sorting technique based on dielectrophoresis(DEP)in a microfluidic chip.Under the joint effect of DEP and fluid drag,white blood cells and circulating tumor cells are separated because of different dielectric properties.First,the mathematical models of device geometry,single cell,DEP force,electric field,and flow field are established to simulate the cell motion.Based on the simulation model,important boundary parameters are discussed to optimize the cell sorting ability of the device.A proper matching relationship between voltage and flow rate is then provided.The inlet and outlet conditions are also investigated to control the particle motion in the flow field.The significance of this study is to verify the cell separating ability of the microfluidic chip,and to provide a logistic design for the separation of rare diseased cells.展开更多
The dielectrophoretic technology has been one of the most frequently applied microfluidic technologies to manipulate particles.The way of a combination of controlled electroosmotic micro-vortices and dielectrophoresis...The dielectrophoretic technology has been one of the most frequently applied microfluidic technologies to manipulate particles.The way of a combination of controlled electroosmotic micro-vortices and dielectrophoresis to manipulate particles of different sizes was proposed in our previous work.However,the thickness of the modulating electrode is neglected.In practice,when the thickness of the modulating electrode increases,the channel flux increases,while the ability of the vortex to capture the particles reduces.In this study,a new method combining the field-modulating electroosmotic vortex and the insulating post is proposed to improve the manipulating capability of the field-modulated electroosmotic vortex to particles.The results indicate that there are three great advantages as the insulating post is placed on the channel wall on the same side of the modulating electrode.First,the capturing ability of the vortex to particles is greater due to the reduction of channel flux and the squeezing effect.Second,the range of regulating channel flux to achieve the optimal separation is extended.Third,the separation efficiency improves since the perfect separation can be achieved at a higher flow rate.Furthermore,the effects of the location and the size of the insulating post on particle separation are analyzed in detail.The present work could provide the reference for the application of the DEP technology.展开更多
基金Project supported by the National Natural Science Foundation of China(No.11172111)
文摘Dielectrophoresis （DEP） is one of the most popular techniques for bio-particle manipulation in microfluidic systems. Traditional calculation of dielectrophoretic forces of single particle based on the approximation of equivalent dipole moment （EDM） cannot be directly applied on the dense particle interactions in an electrical field. The Maxwell stress tensor （MST） method is strictly accurate in the theory for dielectrophoretic forces of particle interaction, but the cumbersome and complicated numerical computation greatly limits its practical applications. A novel iterative dipole moment （IDM） method is pre- sented in this work for calculating the dielectrophoretic forces of particle-particle inter- actions. The accuracy, convergence, and simplicity of the IDM are confirmed by a series of examples of two-particle interaction in a DC/AC electrical field. The results indicate that the IDM is able to calculate the DEP particle interaction forces in good agreement with the MST method. The IDM is a purely analytical operation and does not require complicated numerical computation for solving the differential equations of an electrical field while the particle is moving.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10902105)the Natural Science Foundation of Zhejiang Province (Grant No. 2010R10014)
文摘In this study, the irreversible deposition of microparticles from electrokinetic microfluidic flow in a 90° bend was exami- ned both computationally and theoretically. The flow and electric fields were firstly simulated by the finite volume method, and then a large number of microparticles were injected and traced by the one-way coupling Lagrangian model, incorporating the electrical, hydrodynamic and near-wall repulsive forces exerted on the microparticles. The simulation results indicate that the microparticles with larger size are repelled to close to the upper region of the outer wall under the effect of dielectrophoresis （DEP） force, and the near-wall repulsive force which prevented particles from colliding with the wall would decrease the particles＇ ultimate deposition efficiency. In addition, the specified exponential relationship between the particle deposition efficiency and its relaxation time or par- ticle Stokes number are theoretically derived when the near-wall repulsive force is considered or not.
基金Project supported by the National Natural Science Foundation of China.
文摘<正> In this paper, we have utilized the principle of dielectrophoresis to determine the dielectrophoretic spectra of single levitated tobacco leaf protoplast at various suspending media conductivities (12.5 μS/cm-520 μS/cm) over wide frequencies (10 Hz—15 MHz). From the experimental data, the membrane capacitance of the single protoplast which was 0.40±0.03μF/cm^2 has been obtained and the dipole interaction of two protoplasts in electrofusion has also been analysed. When the external electric field E_c=1.5kV/cm was applied and the frequency was higher than 20 kHz, the dipole interaction pressure ~πd would be much larger than the membrane potential pressure ~πm, and the pressure ~πd could be the main reason for membraue pores. This conclusion will provide a new basis to improve the protocol of cell electrofusion.
基金Project supported by the Basic Research Program of the Korea Science & Engineering Foundation (No. R0120060001027202006)the Basic Science Research Program through the National Research Foundation of Korea (No. 2010-0001882)
文摘This paper presents a high-efficiency technique based on dielectrophoresis (DEP) for assembling metal, semiconductor, and polymer nanorods, which are synthesized by electrochemical deposition (ECD). The assembly patterns of these nanorods (width: 20 nm; length: 7 μm) were designed using a finite element method (FEM) simulation tool. Further, these nanorods were used in our experiment after their assembly patterns were fabricated. The assembly yield was found to be approximately 70% at an AC voltage of 30 Vp-p and at frequencies of 20 and 30 kHz, and the DC voltage prevented the random alignment of the nanorods at the edge of the assembly pattern. Moreover, the above-mentioned nanorods, which had different permittivities, were found to have similar assembly yields. The proposed method can be improved and applied to nanostructure device fabrication.
文摘This numerical study proposes a cell sorting technique based on dielectrophoresis(DEP)in a microfluidic chip.Under the joint effect of DEP and fluid drag,white blood cells and circulating tumor cells are separated because of different dielectric properties.First,the mathematical models of device geometry,single cell,DEP force,electric field,and flow field are established to simulate the cell motion.Based on the simulation model,important boundary parameters are discussed to optimize the cell sorting ability of the device.A proper matching relationship between voltage and flow rate is then provided.The inlet and outlet conditions are also investigated to control the particle motion in the flow field.The significance of this study is to verify the cell separating ability of the microfluidic chip,and to provide a logistic design for the separation of rare diseased cells.
基金Project supported by the National Natural Science Foundation of China(No.11572139)。
文摘The dielectrophoretic technology has been one of the most frequently applied microfluidic technologies to manipulate particles.The way of a combination of controlled electroosmotic micro-vortices and dielectrophoresis to manipulate particles of different sizes was proposed in our previous work.However,the thickness of the modulating electrode is neglected.In practice,when the thickness of the modulating electrode increases,the channel flux increases,while the ability of the vortex to capture the particles reduces.In this study,a new method combining the field-modulating electroosmotic vortex and the insulating post is proposed to improve the manipulating capability of the field-modulated electroosmotic vortex to particles.The results indicate that there are three great advantages as the insulating post is placed on the channel wall on the same side of the modulating electrode.First,the capturing ability of the vortex to particles is greater due to the reduction of channel flux and the squeezing effect.Second,the range of regulating channel flux to achieve the optimal separation is extended.Third,the separation efficiency improves since the perfect separation can be achieved at a higher flow rate.Furthermore,the effects of the location and the size of the insulating post on particle separation are analyzed in detail.The present work could provide the reference for the application of the DEP technology.
