A challenge in chemical engineering is the separation and purification of rare-earth elements and their compounds. We report the design and manufacture of a dielectrophoresis(DEP) microchip of microelectrode arrays. T...A challenge in chemical engineering is the separation and purification of rare-earth elements and their compounds. We report the design and manufacture of a dielectrophoresis(DEP) microchip of microelectrode arrays. This microchip device is constructed in order to use DEP to capture micro-particles of rare-earth oxides in petro-leum. Dielectrophoretic behavior of micro-particles of rare-earth oxides in oil media is explored. The dielectropho-retic effects of particles under different conditions are investigated. It is showed that the prepared microchip is suit-able for use in the investigation of dielectrophoretic responses of the rare-earth oxides in oil media. The factors such as frequency,particle size and valence of rare-earth metal are discussed. When the frequency is fixed,the transla-tion voltage decreases as particle size increases. Lower frequencies are more effective for manipulation of inorganic particles in oil media. Particles of the same rare-earth oxide with different size,as well as particles of different rare-earth oxides,are captured in different regions of the field by regulating DEP conditions. This may be a new method for separation and purification of particles of different rare-earth oxides,as well as classification of particles with different size.展开更多
The electric fields employed for such work are generated using chips, such as planar linear interdigitated arrays or two parallel arrays. However, chip geometries usually affect the investigation of dielectrophoresis ...The electric fields employed for such work are generated using chips, such as planar linear interdigitated arrays or two parallel arrays. However, chip geometries usually affect the investigation of dielectrophoresis （DEP） and electrorotation （ER） significantly, and even may misdirect the theoretical prediction. In order to understand the electrodes geometries effect and provide a suitable range of parameters, three-dimensional simulations for the DEP and ER characterizations on the quadrupolar hyperbolical electrodes are carried out. Influences of the electrodes gaps, cell height, work region, energized voltage and frequencies for the DEP and ER manipulations are analyzed, and the analysis results show that the gaps of the electrodes and the cell height have enormous effects, but the work region is not so important. Moreover, depending on the theoretical analysis, ER experiments for polystyrene microspheres with the diameter of 20 ~m are carried out on two kinds of chips. The experimental results show that the microspheres rotate in the counter-field direction and the maximum rotation speed appears in the megahertz range. In addition, the experimental results are compared with the simulation results, showing that the three-dimensional simulations considering the chip geometries are more accurate than the two-dimensional predictions. This paper provides a new understanding for the theoretical predictions of DEP and ER manipulations, which decreases the difference of the theoretical and experimental results significantly, and will be significant for the lab chip research.展开更多
Microspheres coated with a perfectly conductive surface have many advantages in the applications of biosensors and micro-electromechanical systems. Polystyrene microspheres with the diameter of 10 μm were coated with...Microspheres coated with a perfectly conductive surface have many advantages in the applications of biosensors and micro-electromechanical systems. Polystyrene microspheres with the diameter of 10 μm were coated with a 50 nmthick gold layer using an electroless gold plating approach. Dielectrophoresis （DEP） for bare microspheres and shelled microspheres was theoretically analysed and the real part of the Clausius Mossotti factor was calculated for the two kinds of microspheres. The experiments on the dielectrophoretic characterisation of the uncoated polystyrene microspheres and gold coated polystyrene microspheres （GCPMs） were carried out. Experimental results showed that the gold coated polystyrene microspheres were only acted by a positive dielectrophoretic force when the frequency was below 40M Hz, while the uncoated polystyrene microspheres were governed by a negative dielectrophoretic force in this frequency range. The gold coated polystyrene microspheres were exploited to form the rnicrowire automatically according to their stable dielectrophoretic and electric characterisations.展开更多
The need to continuously separate multiple microparticles is required for the recent development of lab-on-chip technology. Dielectrophoresis（DEP）-based separation device is extensively used in kinds of microfluidic...The need to continuously separate multiple microparticles is required for the recent development of lab-on-chip technology. Dielectrophoresis（DEP）-based separation device is extensively used in kinds of microfluidic applications. However, such conventional DEP-based device is relatively complicated and difficult for fabrication. A concise microfluidic device is presented for effective continuous separation of multiple size particle mixtures. A pair of acupuncture needle electrodes are creatively employed and embedded in a PDMS（poly-dimethylsiloxane） hurdle for generating non-uniform electric field thereby achieving a continuous DEP separation. The separation mechanism is that the incoming particle samples with different sizes experience different negative DEP（n DEP） forces and then they can be transported into different downstream outlets. The DEP characterizations of particles are calculated, and their trajectories are numerically predicted by considering the combined action of the incoming laminar flow and the n DEP force field for guiding the separation experiments. The device performance is verified by successfully separating a three-sized particle mixture, including polystyrene microspheres with diameters of 3 μm, 10 μm and 25 μm. The separation purity is below 70% when the flow rate ratio is less than 3.5 or more than 5.1, while the separation purity can be up to more than 90% when the flow rate ratio is between 3.5 and 5.1 and meanwhile ensure the voltage output falls in between 120 V and 150 V. Such simple DEP-based separation device has extensive applications in future microfluidic systems.展开更多
Here we demonstrate the fabrication of nanometer-sized gaps by assembling single coreshell nanoparticles between metallic nanoelectrodes. Protein coated SiO2@Au coreshell nanopar- tides arc synthesized and positioned ...Here we demonstrate the fabrication of nanometer-sized gaps by assembling single coreshell nanoparticles between metallic nanoelectrodes. Protein coated SiO2@Au coreshell nanopar- tides arc synthesized and positioned between fluorescent molecules-covered electrodes in a controllable way using dielectrophoretic trapping, forming nanogaps sandwiched between nanoparticle and manoelectrodes. Preliminary photoluminescence measurements show that enhanced molecular fluorescence could be detected from the fluorescent molecules inside the nanogaps. These results pave the way for realizing electrically driven molecular fluorescence based on nanogap electrodes.展开更多
Dielectrophoresis impedance measurement(DEPIM)is a powerful tool for bioparticle detection due to its advantages of high efficiency,label-free and low costs.However,the strong electric field may decrease the viability...Dielectrophoresis impedance measurement(DEPIM)is a powerful tool for bioparticle detection due to its advantages of high efficiency,label-free and low costs.However,the strong electric field may decrease the viability of the bioparticle,thus leading to instability of impedance measurement.A new design of biochip is presented with high stable bioparticle detection capabilities by using both negative dielectrophoresis(nDEP)and traveling wave dielectrophoresis(twDEP).In the biochip,a spiral electrode is arranged on the top of channel,while a detector is arranged on the bottom of the channel.The influence factors on the DEP force and twDEP force are investigated by using the basic principle of DEP,based on which,the relationship between Clausius-Mossotti(CM)factor and the frequency of electric field is obtained.The two-dimensional model of the biochip is built by using Comsol Multiphysics.Electric potential distribution,force distribution and particle trajectory in the channel are then obtained by using the simulation model.Finally,both the simulations and experiments are performed to demonstrate that the new biochip can enhance the detection efficiency and reduce the negative effects of electric field on the bioparticles.展开更多
With the development of nanotecbnology, the separation and manipulation of micro-nano-panicles have become a research focus in the field of nano-materials, nielectrophoresis（DEP） is a non-contact technology for the ...With the development of nanotecbnology, the separation and manipulation of micro-nano-panicles have become a research focus in the field of nano-materials, nielectrophoresis（DEP） is a non-contact technology for the separation and manipulation of micro-nano-particles. Here is reported the design and fabrication of a DEP based microchip with microelectrode arrays for capturing micro-particles of inorganic oxides in petroleum. The DEP behavior of micro-particles of inorganic oxides in oil media was explored via this microchip. The microchip shows relatively a good DEP response to inorganic oxides in oil media. Furthermore, much more factors were explored such as fiequency（Hz）, and particle size（μm）, as well as metal valence. As a conclusion, the best frequency is 50 Hz. It is expected to capture panicles with different sizes or separate different oxide panicles by regulating DEP conditions. Thus, a new method could be established for the separation and purification panicles of different oxides, as well as the separation and manipulation of an oxide with different particle sizes.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
In microfluidic technology, dielectrophoresis(DEP) is commonly used to manipulate particles. In this work, the fluid–particle interactions in a microfluidic system are investigated numerically by a finite difference ...In microfluidic technology, dielectrophoresis(DEP) is commonly used to manipulate particles. In this work, the fluid–particle interactions in a microfluidic system are investigated numerically by a finite difference method(FDM) for electric field distribution and a lattice Boltzmann method(LBM) for the fluid flow. In this system, efficient particle manipulation may be realized by combining DEP and field-modulating vortex. The influence of the density(ρ_(p)), radius(γ), and initial position of the particle in the y direction(y_(p0)), and the slip velocity(u_(0)) on the particle manipulation are studied systematically. It is found that compared with the particle without action of DEP force, the particle subjected to a DEP force may be captured by the vortex over a wider range of parameters. In the y direction, as ρ_(p) or γ increases, the particle can be captured more easily by the vortex since it is subjected to a stronger DEP force. When u_(0) is low, particle is more likely to be captured due to the vortex–particle interaction. Furthermore, the flow field around the particle is analyzed to explore the underlying mechanism. The results obtained in the present study may provide theoretical support for engineering applications of field-controlled vortices to manipulate particles.展开更多
The method of using dielectrophoresis （DEP） to assemble graphene between micro-electrodes has been proven to be simple and efficient. We present an optimization method for the kinetic formula of graphene DEP, and di...The method of using dielectrophoresis （DEP） to assemble graphene between micro-electrodes has been proven to be simple and efficient. We present an optimization method for the kinetic formula of graphene DEP, and discuss the simulation of the graphene assembly process based on the finite element method. The simulated results illustrate that the accelerated motion of graphene is in agreement with the distribution of the electric field squared gradient. We also conduct research on the controllable parameters of the DEP assembly such as the alternating current （AC） frequency, the shape of micro-electrodes, and the ratio of the gap between electrodes to the characteristic/geometric length of graphene （λ）. The simulations based on the Clausius-Mossotti factor reveal that both graphene velocity and direction are influenced by the AC frequency. When graphene is close to the electrodes, the shape of micro-electrodes will exert great influence on the velocity of graphene. Also, λ has a great influence on the velocity of graphene. Generally, the velocity of graphene would be greater when λ is in the range of 0.4 0.6. The study is of a theoretical guiding significance in improving the precision and efficiency of the graphene DEP assembly.展开更多
A microchip interdigitated electrode with a sequential signal generator has been developed for traveling wave dielectrophoresis (twDEP) of biological cell suspensions. The electrode was fabricated on a microscope glas...A microchip interdigitated electrode with a sequential signal generator has been developed for traveling wave dielectrophoresis (twDEP) of biological cell suspensions. The electrode was fabricated on a microscope glass slide and coated with a 0.5 μm thickness of gold through a sputtering technique which was designed for large-scale inductions of cells rather than for individual cells as in previous versions of our device. As designed for a representative cell size of 10 μm, the electrode array was 50 μm in width to allow large numbers (>106) of cells to be processed. The sequential signal generator produces an arbitrary AC quadrature-phase to generate traveling electric field for a microchip interdigitated electrode. Each phase signal can be automatically altered and alternated with the other phases within interval time of 0.01-30 seconds (controlled by programming). We demonstrate the system could be used to estimate the dielectric properties of the yeast Saccharomyces cerivisiae TISTR 5088, the green alga Tetraselmis sp. and human red blood cells (HRBCs) through curve-fitting of dielectro- phoretic velocities and critical frequencies.展开更多
The effects of electric field and ultrasonication on the deposition and alignment of single-walled carbon nanotubes (SWCNTs) across a 10 μm electrode gap have been studied. It was found that a frequency of ~1 MHz of ...The effects of electric field and ultrasonication on the deposition and alignment of single-walled carbon nanotubes (SWCNTs) across a 10 μm electrode gap have been studied. It was found that a frequency of ~1 MHz of the applied field yields the largest current independent of the magnitude of the voltage or the ultrasonication time of the sample. Increasing the ultrasonication time of a SWCNT solution changes the I-V characteristics of the deposited nanotubes from linear to nonlinear for all the voltages and frequencies of the applied field. Even in the absence of an electric field, SWCNTs bridged the electrode gap up to a critical sonication time which depends on the concentration of nanotubes in the solution.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 nonequilibrium molecular dynamics (MD) method was used to model the nanocolloids and the solvent particles. By introducing a non-uniform electric field, colloids were polarized to have opposite polarities. Separat...The nonequilibrium molecular dynamics (MD) method was used to model the nanocolloids and the solvent particles. By introducing a non-uniform electric field, colloids were polarized to have opposite polarities. Separation of colloids driven by dielectrophoresis (DEP) could be seen clearly under a strong electric field at low temperatures. Analyzing the ratio of DEP velocities of colloids to thermal velocities of neutral solvent particles showed that when the ratio was correspondingly big, collision between colloids and solvent particles would be intense, making the DEP velocity of colloids fluctuate frequently. By changing the electric field strength, it was found that the enhancement of electric field strength would quicken the separation of colloids. But when the electric field strength increased to a certain degree, the separation motion would be slow because of the strong friction resistance of the solvent particles to the colloids. Moreover, studying the separation reason of colloids based on the potential energy showed that after colloids were polarized, the attractive potential energy among the colloids would be weaker than before, while the increase of temperature would reduce the attractive potential energy and increase the repulsive potential energy, which accorded with the DLVO theory.展开更多
On the basis of the research on the status and problems of micro/nano bio-particles manipulation using dielectrophoresis, the theoretical basis and the model simulation of micro/nano bio-particles manipu-lation using ...On the basis of the research on the status and problems of micro/nano bio-particles manipulation using dielectrophoresis, the theoretical basis and the model simulation of micro/nano bio-particles manipu-lation using light-induced dielectrophoresis were discussed. The space distribution of electric field and dielectrophoresis forces in different heights were also obtained. On this basis, the core component of the micro manipulation system, that is, photoconductive layer of the chip, was completed in the mate-rial selection, fabricating process and performance analysis testing. Then the voltage drop of the sus-pension and the effective voltage frequency spectrum were obtained. Finally, by combining the machine vision detection with real-time tracking system, the micro/nano bio-particles manipulation platform based on the light-induced dielectrophoreisis was established, and then the manipulations for micro/nano bio-particles, such as quick collection, transport, separation, were implemented. This provided a basis for rapid, accurate, and low-cost detection of serious diseases based on the micro-fluidic biochip and early diagnosis.展开更多
The key problem to be solved for the dielectrophoresis (DEP) application is to provide dynamically reconfigurable microelectrodes and low-cost methodology for bioparticle manipulation.The emergence of optically induce...The key problem to be solved for the dielectrophoresis (DEP) application is to provide dynamically reconfigurable microelectrodes and low-cost methodology for bioparticle manipulation.The emergence of optically induced DEP (ODEP) based on photoconductive effect provides a potential solution for the above problem.In 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 analyzed.The 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 solution.The manipulation efficiency can increase by more than 50% via increasing the optical line width.Moreover,the efficiency is obviously affected by the inclination angle of the optical oblique lines in the manipulation of particle focusing.Additionally,the maximum velocity of particles increases with the increment of the inside radius and the thickness of the optical trapping ring.Particle 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.展开更多
Dielectrophoresis(DEP)describes the motion of suspended objects when exposed to an inhomogeneous electric field.It has been successful as a method for parallel and site-selective assembling of nanotubes from a dispers...Dielectrophoresis(DEP)describes the motion of suspended objects when exposed to an inhomogeneous electric field.It has been successful as a method for parallel and site-selective assembling of nanotubes from a dispersion into a sophisticated device architecture.Researchers have conducted extensive works to understand the DEP of nanotubes in aqueous ionic surfactant solutions.However,only recently,DEP was applied to polymer-wrapped single-walled carbon nanotubes(SWCNTs)in organic solvents due to the availability of ultra-pure SWCNT content.In this paper,the focus is on the difference between the DEP in aqueous and organic solutions.It starts with an introduction into the DEP of carbon nanotubes(CNT-DEP)to provide a comprehensive,in-depth theoretical background before discussing in detail the experimental procedures and conditions.For academic interests,this work focuses on the CNT-DEP deposition scheme,discusses the importance of the electrical double layer,and employs finite element simulations to optimize CNT-DEP deposition condition with respect to the experimental observation.An important outcome is an understanding of why DEP in organic solvents allows for the deposition and alignment of SWCNTs in low-frequency and even static electric fields,and why the response of semiconducting SWCNTs(s-SWCNTs)is strongly enhanced in non-conducting,weakly polarizable media.Strategies to further improve CNT-DEP for s-SWCNT-relevant applications are given as well.Overall,this work should serve as a practical guideline to select the appropriate setting for effective CNT DEPs.展开更多
Dielectrophoresis(DEP)was combined with adsorption(ADS)to simultaneously and effectively remove Cd^2+ and Pb^2+ species from aqueous solution.To implement the process,bentonite particles of submicro-meter size were us...Dielectrophoresis(DEP)was combined with adsorption(ADS)to simultaneously and effectively remove Cd^2+ and Pb^2+ species from aqueous solution.To implement the process,bentonite particles of submicro-meter size were used to first adsorb the heavy metal ions.These particles were subsequently trapped and removed by DEP.The effects of the adsorbent dosage,DEP cell voltage and the capture pool numbers on the removal rate were investigated in batch processes,which allowed us to determine the optimal experimental conditions.The high removal efficiency,97.3% and 99.9% for Cd^2+ and Pb^2+,respectively,were achieved when the ions are coexisting in the system.The microstructure of bentonite particles before and after ADS/DEP was examined by scanning electron microscopy.Our results suggest that the dielectrophoresis-assisted adsorption method has a high capability to remove the heavy metals from wastewater.展开更多
In recent years the microchannel heat exchangers have been applied in a great variety of technical areas. One of the problems, which exist in the microcharmel technology is the flow instabilities, including fluid mald...In recent years the microchannel heat exchangers have been applied in a great variety of technical areas. One of the problems, which exist in the microcharmel technology is the flow instabilities, including fluid maldistribution in the microcharmels array for the case of two-phase flow especially in micro-evaporators. One of the ways to solve this problem is flow rate control at the microcharmel inlet. However, due to very small inlet to the array of microchannels the classic flow restriction device （with moving mechanical parts） will be difficult to apply. The new device for the flow rate control based on the dielectrophoresis force was presented in the paper. Experimet^tal research results of using this device for refrigerant flow control was presented in the paper. The experimentally obtained relationships between applied voltages and frequencies and flow rates were presented showing opportunity for applying such method for refrigerants and other volatile fluids.展开更多
According to the equivalent circuit model(ECM),finite element model(FEM) and physical experiment,the LIDEP force induced by the spatial variations of the phase of AC electric fields produced by the bright and dark reg...According to the equivalent circuit model(ECM),finite element model(FEM) and physical experiment,the LIDEP force induced by the spatial variations of the phase of AC electric fields produced by the bright and dark regions on the photoconductive layer was demonstrated.Besides,the phenomenon of the light-induced electro-rotation(LIER) caused by the light-induced rotating electric field was confirmed numerically and experimentally for the first time.It may be helpful to go out of the dilemma that only the dipole moment model,based on the effect of light-induced partial potentials,can be used for LIDEP theoretical calculation currently.Through the FEM simulation and the electro-rotating experiment of yeast cells,it was found that the direction of yeast's LIER is relevant to the distance between its location and the edge of optical electrode,and the spin velocity of LIER is inversely proportional to that distance.Nevertheless,the LIER torques in the three-electrode mode show a non-uniform distribution where the LIDEP forces are harmful for a particle spinning stably around a fixed axis.Moreover,a four-electrode double-layer mode was proposed for the first time and the finite element simulation results agreed with the expected design,suggesting a new way for the dielectric spectrum measurement based on LIER.展开更多
基金Supported by the 985 Foundation of Central University for Nationalities（CUN985-3-3） the National Natural Science Foundation of China（90305011）
文摘A challenge in chemical engineering is the separation and purification of rare-earth elements and their compounds. We report the design and manufacture of a dielectrophoresis(DEP) microchip of microelectrode arrays. This microchip device is constructed in order to use DEP to capture micro-particles of rare-earth oxides in petro-leum. Dielectrophoretic behavior of micro-particles of rare-earth oxides in oil media is explored. The dielectropho-retic effects of particles under different conditions are investigated. It is showed that the prepared microchip is suit-able for use in the investigation of dielectrophoretic responses of the rare-earth oxides in oil media. The factors such as frequency,particle size and valence of rare-earth metal are discussed. When the frequency is fixed,the transla-tion voltage decreases as particle size increases. Lower frequencies are more effective for manipulation of inorganic particles in oil media. Particles of the same rare-earth oxide with different size,as well as particles of different rare-earth oxides,are captured in different regions of the field by regulating DEP conditions. This may be a new method for separation and purification of particles of different rare-earth oxides,as well as classification of particles with different size.
基金supported by National Natural Science Foundation of China(Grant No.51305106)The State Key Lab of Fluid Power Transmission and Control of Zhejiang University,China(Grant No.GZKF-201107)
文摘The electric fields employed for such work are generated using chips, such as planar linear interdigitated arrays or two parallel arrays. However, chip geometries usually affect the investigation of dielectrophoresis （DEP） and electrorotation （ER） significantly, and even may misdirect the theoretical prediction. In order to understand the electrodes geometries effect and provide a suitable range of parameters, three-dimensional simulations for the DEP and ER characterizations on the quadrupolar hyperbolical electrodes are carried out. Influences of the electrodes gaps, cell height, work region, energized voltage and frequencies for the DEP and ER manipulations are analyzed, and the analysis results show that the gaps of the electrodes and the cell height have enormous effects, but the work region is not so important. Moreover, depending on the theoretical analysis, ER experiments for polystyrene microspheres with the diameter of 20 ~m are carried out on two kinds of chips. The experimental results show that the microspheres rotate in the counter-field direction and the maximum rotation speed appears in the megahertz range. In addition, the experimental results are compared with the simulation results, showing that the three-dimensional simulations considering the chip geometries are more accurate than the two-dimensional predictions. This paper provides a new understanding for the theoretical predictions of DEP and ER manipulations, which decreases the difference of the theoretical and experimental results significantly, and will be significant for the lab chip research.
基金Project supported by the National Natural Science Foundation of China (Grant No. 51075087)the State Key Laboratory of Fluid Power Transmission and Control,ZheJiang University of China (Grnat No. GZKF-201004)the China Scholarship Council(Grant No. 2009612129)
文摘Microspheres coated with a perfectly conductive surface have many advantages in the applications of biosensors and micro-electromechanical systems. Polystyrene microspheres with the diameter of 10 μm were coated with a 50 nmthick gold layer using an electroless gold plating approach. Dielectrophoresis （DEP） for bare microspheres and shelled microspheres was theoretically analysed and the real part of the Clausius Mossotti factor was calculated for the two kinds of microspheres. The experiments on the dielectrophoretic characterisation of the uncoated polystyrene microspheres and gold coated polystyrene microspheres （GCPMs） were carried out. Experimental results showed that the gold coated polystyrene microspheres were only acted by a positive dielectrophoretic force when the frequency was below 40M Hz, while the uncoated polystyrene microspheres were governed by a negative dielectrophoretic force in this frequency range. The gold coated polystyrene microspheres were exploited to form the rnicrowire automatically according to their stable dielectrophoretic and electric characterisations.
基金Supported by National Natural Science Foundation of China(Grant No.51305106)Fundamental Research Funds for the Central Universities,China(Grant Nos.HIT.NSRIF.2014058,HIT.IBRSEM.201319)Open Foundation of State Key Laboratory of Fluid Power Transmission and Control,China(GZKF-201402)
文摘The need to continuously separate multiple microparticles is required for the recent development of lab-on-chip technology. Dielectrophoresis（DEP）-based separation device is extensively used in kinds of microfluidic applications. However, such conventional DEP-based device is relatively complicated and difficult for fabrication. A concise microfluidic device is presented for effective continuous separation of multiple size particle mixtures. A pair of acupuncture needle electrodes are creatively employed and embedded in a PDMS（poly-dimethylsiloxane） hurdle for generating non-uniform electric field thereby achieving a continuous DEP separation. The separation mechanism is that the incoming particle samples with different sizes experience different negative DEP（n DEP） forces and then they can be transported into different downstream outlets. The DEP characterizations of particles are calculated, and their trajectories are numerically predicted by considering the combined action of the incoming laminar flow and the n DEP force field for guiding the separation experiments. The device performance is verified by successfully separating a three-sized particle mixture, including polystyrene microspheres with diameters of 3 μm, 10 μm and 25 μm. The separation purity is below 70% when the flow rate ratio is less than 3.5 or more than 5.1, while the separation purity can be up to more than 90% when the flow rate ratio is between 3.5 and 5.1 and meanwhile ensure the voltage output falls in between 120 V and 150 V. Such simple DEP-based separation device has extensive applications in future microfluidic systems.
文摘Here we demonstrate the fabrication of nanometer-sized gaps by assembling single coreshell nanoparticles between metallic nanoelectrodes. Protein coated SiO2@Au coreshell nanopar- tides arc synthesized and positioned between fluorescent molecules-covered electrodes in a controllable way using dielectrophoretic trapping, forming nanogaps sandwiched between nanoparticle and manoelectrodes. Preliminary photoluminescence measurements show that enhanced molecular fluorescence could be detected from the fluorescent molecules inside the nanogaps. These results pave the way for realizing electrically driven molecular fluorescence based on nanogap electrodes.
基金supported by the Project of Youth Fund of National Natural Science Foundation (No. 61203208)the National Natural Science Foundation of China(No.61327802)
文摘Dielectrophoresis impedance measurement(DEPIM)is a powerful tool for bioparticle detection due to its advantages of high efficiency,label-free and low costs.However,the strong electric field may decrease the viability of the bioparticle,thus leading to instability of impedance measurement.A new design of biochip is presented with high stable bioparticle detection capabilities by using both negative dielectrophoresis(nDEP)and traveling wave dielectrophoresis(twDEP).In the biochip,a spiral electrode is arranged on the top of channel,while a detector is arranged on the bottom of the channel.The influence factors on the DEP force and twDEP force are investigated by using the basic principle of DEP,based on which,the relationship between Clausius-Mossotti(CM)factor and the frequency of electric field is obtained.The two-dimensional model of the biochip is built by using Comsol Multiphysics.Electric potential distribution,force distribution and particle trajectory in the channel are then obtained by using the simulation model.Finally,both the simulations and experiments are performed to demonstrate that the new biochip can enhance the detection efficiency and reduce the negative effects of electric field on the bioparticles.
基金Supported by the National Natural Science Foundation of China(No.90305011)the"985"Foundation of Central University for Nationalities(No.cun985-3-3)
文摘With the development of nanotecbnology, the separation and manipulation of micro-nano-panicles have become a research focus in the field of nano-materials, nielectrophoresis（DEP） is a non-contact technology for the separation and manipulation of micro-nano-particles. Here is reported the design and fabrication of a DEP based microchip with microelectrode arrays for capturing micro-particles of inorganic oxides in petroleum. The DEP behavior of micro-particles of inorganic oxides in oil media was explored via this microchip. The microchip shows relatively a good DEP response to inorganic oxides in oil media. Furthermore, much more factors were explored such as fiequency（Hz）, and particle size（μm）, as well as metal valence. As a conclusion, the best frequency is 50 Hz. It is expected to capture panicles with different sizes or separate different oxide panicles by regulating DEP conditions. Thus, a new method could be established for the separation and purification panicles of different oxides, as well as the separation and manipulation of an oxide with different particle sizes.
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.
基金Project supported by the National Natural Science Foundation of China (Granmt Nos. 11572139, 11872187, and 12072125)。
文摘In microfluidic technology, dielectrophoresis(DEP) is commonly used to manipulate particles. In this work, the fluid–particle interactions in a microfluidic system are investigated numerically by a finite difference method(FDM) for electric field distribution and a lattice Boltzmann method(LBM) for the fluid flow. In this system, efficient particle manipulation may be realized by combining DEP and field-modulating vortex. The influence of the density(ρ_(p)), radius(γ), and initial position of the particle in the y direction(y_(p0)), and the slip velocity(u_(0)) on the particle manipulation are studied systematically. It is found that compared with the particle without action of DEP force, the particle subjected to a DEP force may be captured by the vortex over a wider range of parameters. In the y direction, as ρ_(p) or γ increases, the particle can be captured more easily by the vortex since it is subjected to a stronger DEP force. When u_(0) is low, particle is more likely to be captured due to the vortex–particle interaction. Furthermore, the flow field around the particle is analyzed to explore the underlying mechanism. The results obtained in the present study may provide theoretical support for engineering applications of field-controlled vortices to manipulate particles.
基金Supported by the Basic Research Project of Shanxi Province under Grant No 2015021092the National Natural Science Foundation of China under Grant Nos 61471255,61474079,61501316,51505324 and 51622507the National High-Technology Research and Development Program of China under Grant No 2015AA042601
文摘The method of using dielectrophoresis （DEP） to assemble graphene between micro-electrodes has been proven to be simple and efficient. We present an optimization method for the kinetic formula of graphene DEP, and discuss the simulation of the graphene assembly process based on the finite element method. The simulated results illustrate that the accelerated motion of graphene is in agreement with the distribution of the electric field squared gradient. We also conduct research on the controllable parameters of the DEP assembly such as the alternating current （AC） frequency, the shape of micro-electrodes, and the ratio of the gap between electrodes to the characteristic/geometric length of graphene （λ）. The simulations based on the Clausius-Mossotti factor reveal that both graphene velocity and direction are influenced by the AC frequency. When graphene is close to the electrodes, the shape of micro-electrodes will exert great influence on the velocity of graphene. Also, λ has a great influence on the velocity of graphene. Generally, the velocity of graphene would be greater when λ is in the range of 0.4 0.6. The study is of a theoretical guiding significance in improving the precision and efficiency of the graphene DEP assembly.
文摘A microchip interdigitated electrode with a sequential signal generator has been developed for traveling wave dielectrophoresis (twDEP) of biological cell suspensions. The electrode was fabricated on a microscope glass slide and coated with a 0.5 μm thickness of gold through a sputtering technique which was designed for large-scale inductions of cells rather than for individual cells as in previous versions of our device. As designed for a representative cell size of 10 μm, the electrode array was 50 μm in width to allow large numbers (>106) of cells to be processed. The sequential signal generator produces an arbitrary AC quadrature-phase to generate traveling electric field for a microchip interdigitated electrode. Each phase signal can be automatically altered and alternated with the other phases within interval time of 0.01-30 seconds (controlled by programming). We demonstrate the system could be used to estimate the dielectric properties of the yeast Saccharomyces cerivisiae TISTR 5088, the green alga Tetraselmis sp. and human red blood cells (HRBCs) through curve-fitting of dielectro- phoretic velocities and critical frequencies.
文摘The effects of electric field and ultrasonication on the deposition and alignment of single-walled carbon nanotubes (SWCNTs) across a 10 μm electrode gap have been studied. It was found that a frequency of ~1 MHz of the applied field yields the largest current independent of the magnitude of the voltage or the ultrasonication time of the sample. Increasing the ultrasonication time of a SWCNT solution changes the I-V characteristics of the deposited nanotubes from linear to nonlinear for all the voltages and frequencies of the applied field. Even in the absence of an electric field, SWCNTs bridged the electrode gap up to a critical sonication time which depends on the concentration of nanotubes in the solution.
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Supported by the National Hi-Tech Research and Derelopment Program of China("863"Project)(Grant No.2006AA04Z351)the National Natural Science Foundation of China(Grant Nos.50675033,30770553)
文摘The nonequilibrium molecular dynamics (MD) method was used to model the nanocolloids and the solvent particles. By introducing a non-uniform electric field, colloids were polarized to have opposite polarities. Separation of colloids driven by dielectrophoresis (DEP) could be seen clearly under a strong electric field at low temperatures. Analyzing the ratio of DEP velocities of colloids to thermal velocities of neutral solvent particles showed that when the ratio was correspondingly big, collision between colloids and solvent particles would be intense, making the DEP velocity of colloids fluctuate frequently. By changing the electric field strength, it was found that the enhancement of electric field strength would quicken the separation of colloids. But when the electric field strength increased to a certain degree, the separation motion would be slow because of the strong friction resistance of the solvent particles to the colloids. Moreover, studying the separation reason of colloids based on the potential energy showed that after colloids were polarized, the attractive potential energy among the colloids would be weaker than before, while the increase of temperature would reduce the attractive potential energy and increase the repulsive potential energy, which accorded with the DLVO theory.
基金Supported by the National High Technology Research and Development Program of China ("863" Program) (Grant No. 2006AA04Z351)the National Natural Science Foundation of China (Grant Nos. 50675033, 30770553)
文摘On the basis of the research on the status and problems of micro/nano bio-particles manipulation using dielectrophoresis, the theoretical basis and the model simulation of micro/nano bio-particles manipu-lation using light-induced dielectrophoresis were discussed. The space distribution of electric field and dielectrophoresis forces in different heights were also obtained. On this basis, the core component of the micro manipulation system, that is, photoconductive layer of the chip, was completed in the mate-rial selection, fabricating process and performance analysis testing. Then the voltage drop of the sus-pension and the effective voltage frequency spectrum were obtained. Finally, by combining the machine vision detection with real-time tracking system, the micro/nano bio-particles manipulation platform based on the light-induced dielectrophoreisis was established, and then the manipulations for micro/nano bio-particles, such as quick collection, transport, separation, were implemented. This provided a basis for rapid, accurate, and low-cost detection of serious diseases based on the micro-fluidic biochip and early diagnosis.
基金supported by the National High Technology Research and Development Program of China ("863" Program) (Grant No. 2009AA04Z310)the National Natural Science Foundation of China (Grant Nos. 30770553, 50805022)
文摘The key problem to be solved for the dielectrophoresis (DEP) application is to provide dynamically reconfigurable microelectrodes and low-cost methodology for bioparticle manipulation.The emergence of optically induced DEP (ODEP) based on photoconductive effect provides a potential solution for the above problem.In 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 analyzed.The 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 solution.The manipulation efficiency can increase by more than 50% via increasing the optical line width.Moreover,the efficiency is obviously affected by the inclination angle of the optical oblique lines in the manipulation of particle focusing.Additionally,the maximum velocity of particles increases with the increment of the inside radius and the thickness of the optical trapping ring.Particle 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.
基金S.Flavel acknowledges support from the Deutsche Forschungsgemeinschafts Emmy Noether Program under grant number FL 834/1-1.
文摘Dielectrophoresis(DEP)describes the motion of suspended objects when exposed to an inhomogeneous electric field.It has been successful as a method for parallel and site-selective assembling of nanotubes from a dispersion into a sophisticated device architecture.Researchers have conducted extensive works to understand the DEP of nanotubes in aqueous ionic surfactant solutions.However,only recently,DEP was applied to polymer-wrapped single-walled carbon nanotubes(SWCNTs)in organic solvents due to the availability of ultra-pure SWCNT content.In this paper,the focus is on the difference between the DEP in aqueous and organic solutions.It starts with an introduction into the DEP of carbon nanotubes(CNT-DEP)to provide a comprehensive,in-depth theoretical background before discussing in detail the experimental procedures and conditions.For academic interests,this work focuses on the CNT-DEP deposition scheme,discusses the importance of the electrical double layer,and employs finite element simulations to optimize CNT-DEP deposition condition with respect to the experimental observation.An important outcome is an understanding of why DEP in organic solvents allows for the deposition and alignment of SWCNTs in low-frequency and even static electric fields,and why the response of semiconducting SWCNTs(s-SWCNTs)is strongly enhanced in non-conducting,weakly polarizable media.Strategies to further improve CNT-DEP for s-SWCNT-relevant applications are given as well.Overall,this work should serve as a practical guideline to select the appropriate setting for effective CNT DEPs.
基金the National Major Science and Technology Program for Water Pollution Control and Treatment(No.2017ZX07101-002)the Fundamental Research Funds for the Central Universities(No.2016SHXY06)the National Natural Science Foundation of China(Grant No.51609271).
文摘Dielectrophoresis(DEP)was combined with adsorption(ADS)to simultaneously and effectively remove Cd^2+ and Pb^2+ species from aqueous solution.To implement the process,bentonite particles of submicro-meter size were used to first adsorb the heavy metal ions.These particles were subsequently trapped and removed by DEP.The effects of the adsorbent dosage,DEP cell voltage and the capture pool numbers on the removal rate were investigated in batch processes,which allowed us to determine the optimal experimental conditions.The high removal efficiency,97.3% and 99.9% for Cd^2+ and Pb^2+,respectively,were achieved when the ions are coexisting in the system.The microstructure of bentonite particles before and after ADS/DEP was examined by scanning electron microscopy.Our results suggest that the dielectrophoresis-assisted adsorption method has a high capability to remove the heavy metals from wastewater.
基金supported by Polish Ministry of Science and Higher Education within the Project No.3969/T02/ 2009/36
文摘In recent years the microchannel heat exchangers have been applied in a great variety of technical areas. One of the problems, which exist in the microcharmel technology is the flow instabilities, including fluid maldistribution in the microcharmels array for the case of two-phase flow especially in micro-evaporators. One of the ways to solve this problem is flow rate control at the microcharmel inlet. However, due to very small inlet to the array of microchannels the classic flow restriction device （with moving mechanical parts） will be difficult to apply. The new device for the flow rate control based on the dielectrophoresis force was presented in the paper. Experimet^tal research results of using this device for refrigerant flow control was presented in the paper. The experimentally obtained relationships between applied voltages and frequencies and flow rates were presented showing opportunity for applying such method for refrigerants and other volatile fluids.
基金supported by the Major Program of the National Natural Science Foundation of China (Grant No. 91023024)the New Century Elitist Program by Ministry of Education of China (Grant No.NCET-07-0180)the Technology Supported Research Program from Jiangsu Province (Grant No. BE2009054)
文摘According to the equivalent circuit model(ECM),finite element model(FEM) and physical experiment,the LIDEP force induced by the spatial variations of the phase of AC electric fields produced by the bright and dark regions on the photoconductive layer was demonstrated.Besides,the phenomenon of the light-induced electro-rotation(LIER) caused by the light-induced rotating electric field was confirmed numerically and experimentally for the first time.It may be helpful to go out of the dilemma that only the dipole moment model,based on the effect of light-induced partial potentials,can be used for LIDEP theoretical calculation currently.Through the FEM simulation and the electro-rotating experiment of yeast cells,it was found that the direction of yeast's LIER is relevant to the distance between its location and the edge of optical electrode,and the spin velocity of LIER is inversely proportional to that distance.Nevertheless,the LIER torques in the three-electrode mode show a non-uniform distribution where the LIDEP forces are harmful for a particle spinning stably around a fixed axis.Moreover,a four-electrode double-layer mode was proposed for the first time and the finite element simulation results agreed with the expected design,suggesting a new way for the dielectric spectrum measurement based on LIER.
