Creation of single-particle environment by positive dielectrophoresis and liquid dielectrophoresis

Two electrical mechanisms for manipulating particles and fluids, dielectrophoresis (DEP) and liquid dielectrophoresis (LDEP), are integrated in a microfluidic chip for creating the single-particle environment. The fluid is activated by LDEP with a 100-kHz/240-V_pp signal. When the single polystyrene bead approaches the trapping area, positive DEP force is utilized to capture and immobilize the bead. After trapping the bead, the process of liquid cutting and droplet creation is employed to create a droplet containing a single bead by LDEP with a 100-kHz/320-V_pp signal.     

Integrated liquid and droplet dielectrophoresis for biochemical assays

Surface microfluidic systems have emerged as an attractive alternative to conventional closed-channel microfluidic devices. In many such systems, electric fields are leveraged for the manipulation and transport of discrete nanoliter droplets on open planar surfaces. The present research work discusses dielectrophoretic liquid and droplet actuations, which provide an attractive methodology for dispensing and manipulating nanoliter and picoliter droplets on planar surfaces. We demonstrate the integration of two independent sample actuation schemes, namely liquid dielectrophoresis (L-DEP) and droplet dielectrophoresis, and furthermore validate its applicability through model biochemical assays (DNA-PicoGreen^® assay and DNA FRET assay). We also describe and present ‘tapering L-DEP’ actuation scheme, whereby we demonstrate how to simultaneously create multiple droplets of different sizes and volumes in the range of nanoliter and picoliters, from a given larger parent sample droplet.     

Characterization and modeling of a microfluidic dielectrophoresis filter for biological species

Microfabricated interdigitated electrode array is a convenient form of electrode geometry for dielectrophoretic trapping of particles and biological entities such as cells and bacteria within microfluidic biochips. We present experimental results and finite element modeling of the holding forces for both positive and negative dielectrophoretic traps on microfabricated interdigitated electrodes within a microfluidic biochip fabricated in silicon with a 12-/spl mu/m-deep chamber. Anodic bonding was used to close the channels with a glass cover. An Experimental protocol was then used to measure the voltages necessary to capture different particles (polystyrene beads, yeast cells, spores and bacteria) against destabilizing fluid flows at a given frequency. The experimental results and those from modeling are found to be in close agreement, validating our ability to model the dielectrophoretic filter for bacteria, spores, yeast cells, and polystyrene beads. This knowledge can be very useful in designing and operating a dielectrophoretic barrier or filter to sort and select particles entering the microfluidic devices for further analysis.     

Electrical and dielectric characterization of a biological liquid using an interdigitated microelectrodes

Microsystem Technologies - In this work, we propose a geometrical analysis of a biosensor with microelectrodes of interdigitated structures, based on the method of impedance spectroscopy in the...     

Optimal power distribution control for a network of fuel cell stacks

In power networks, where multiple fuel cell stacks are employed in a series-parallel configuration to deliver the required power, optimal sharing of the power demand between different stacks is an important problem. This is because the total current collectively produced by all the stacks is directly proportional to the fuel utilization, through stoichiometry. As a result, one would like to produce the required power while minimizing the total current produced. In this paper, an optimization formulation is proposed for this power distribution control problem. An algorithm that identifies the globally optimal solution for this problem is developed. Through an analysis of the KKT conditions, the solution to the optimization problem is decomposed into off-line and on-line computations. The on-line computations reduce to solving a nonlinear equation. For an application with a specific V–I function derived from data, we show that analytical solutions exist for on-line computations. We also discuss the wider applicability of the proposed approach for similar problems in other domains.     

Development of a 3-D measurement and evaluation system for facial forms with a liquid crystal range finder

A 3-D measurement and evaluation system for facial forms was developed with a liquid crystal range finder (LCRF). Its mechanical resolution was approximately/= 0.4 mm, and it was capable of measuring >30000 points from the entire facial surface in one second. An original program was developed to identify facial landmarks using not only linear distances, but also 3D-curvatures and discriminant analysis of the RGB data. With this program, the 3-D identification of anthropometrical points became possible with high accuracy. Due to the rapidity of the measuring apparatus and morphological evaluation system, it became possible to analyze the facial forms of infants such as cleft lip patients three dimensionally, without any sedation. Therefore, 97 normal infants (mean: 4.3 months of age) were measured and analyzed with this system. A cleft lip infant was measured and compared with the normal infants before and after cleft lip surgery, and the improved points and remaining problems were clearly recognized.     

Habitat prediction and knowledge extraction for spawning European grayling (Thymallus thymallus L.) using a broad range of species distribution models

This study aims to apply seven data-driven methods (i.e. artificial neural networks [ANNs], classification and regression trees [CARTs], fuzzy habitat suitability models [FHSMs], generalized additive models [GAMs], generalized linear models [GLMs], random forests [RF] and support vector machines [SVMs]) to develop data-driven species distribution models (SDMs) for spawning European grayling (Thymallus thymallus), and to compare the predictive performance and the ecological relevance, quantified by the habitat information retrieved from these SDMs (i.e. variable importance and habitat suitability curves [HSCs]). The results suggest RF to yield the most accurate SDM, followed by SVM, CART, ANN, GAM, FHSM and GLM. However, inconsistencies between different performance measures were observed, indicating that different models may obtain a high score on a particular aspect and perform worse on other aspects. Despite their lower predictive ability, GAM, GLM and FHSM proved to be useful, since HSCs could be obtained and thus these techniques allow testing of ecological relevance and habitat suitability. Water depth and flow velocity appeared to be important variables for spawning grayling. The HSCs clearly indicate higher habitat suitability at a lower water depth, a low to medium flow velocity and a higher percentage of medium-sized gravel, whereas the models disagreed on the habitat suitability for the percentage of small-sized gravel. These findings demonstrate the applicability of data-driven SDMs for both habitat prediction and ecological knowledge extraction that are useful for management of a target species.     

Purification of a droplet using negative dielectrophoresis traps in digital microfluidics

The development of techniques for manipulating particles and integrating them into the digital microfluidic (DMF) devices has been the subject of several studies in recent years. This paper presents a dielectrophoretic-based method that uses triangular traps to manipulate particles and purify a droplet in DMF platforms. Numerical and experimental studies are conducted to show the effectiveness of the proposed trap geometry which is also compatible with the other operators in the DMF platform. The triangular trap geometry is used to move the polystyrene particles to one side of the trap using negative dielectrophoresis (nDEP). The droplet is then split into two smaller droplets with very low and high concentrations of particles using the electrowetting on dielectric technique. The average velocity of the particles (as they move along the trap) as a function of the vertex angle of the triangular trap and the gap between the top and bottom plate is examined. It is observed that the vertex angle of the trap plays more important role on the motion of the particles than the gap. Thus, to enhance the motion of the particles and minimize the effect of splitting on the purification process, the vertex angle and the slope of the side arms of the triangular trap are modified based on the results of the numerical model simulating the dielectrophoretic force on the particle. The enhanced geometry is fabricated and tested experimentally to show the effectiveness and ease-of-use of the proposed technique in purifying (or concentrating) a droplet in DMF. The results show that using the proposed nDEP electrode geometry purification (or concentration) can be performed with the efficiency of 90 %.     

150mL活塞式液体微小流量计量标准装置的研究

针对现有液体流量计量标准装置测量范围的限制不能适应微流体计量的需求,研究开发了一种用于生物医药领域的150mL活塞式液体微小流量计量标准装置.介绍了该标准装置的结构、检定原理和检定过程;根据检定需求设计了一种基于LabVIEW平台和PLC的检定系统软硬件.利用LabVIEW平台设计上位机的检定程序,用于实现人机交互、检...     

Detection of a small shift in a broad distribution

Statistical methods for the extraction of a small shift in broad data distributions are examined by means of Monte Carlo simulations. This work was originally motivated by the CERN neutrino beam to Gran Sasso (CNGS) experiment for which the OPERA detector collaboration reported a time shift in a broad distribution with an accuracy of ±7.8 ns, while the fluctuation of the average time turns with ±23.8 ns out to be much larger. Although the physical result of a big shift has been withdrawn, statistical methods that make an identification in a broad distribution with such a small error possible remain of interest.     

STFBC用于MIMO-OFDM性能分析

本文对具有时域和空域分集的通信方案以及同时具有时域、空域和频域分集的通信方案的性能进行了对比。在对比中采用相同的发射速率,两种方案分别为使用2个发射天线、1个接收天线的MISO系统以及使用2个发射天线、2个接收天线的MIMO系统。两种方案中均使用了OFDM技术。模拟实验给出了对应一系列固定无线应用信道模型的模拟结果。     

Mining multiple-level spatial association rules for objects with a broad boundary

Spatial data mining, i.e., mining knowledge from large amounts of spatial data, is a demanding field since huge amounts of spatial data have been collected in various applications, ranging from remote sensing to geographical information systems (GIS), computer cartography, environmental assessment and planning. The collected data far exceeds people's ability to analyze it. Thus, new and efficient methods are needed to discover knowledge from large spatial databases. Most of the spatial data mining methods do not take into account the uncertainty of spatial information. In our work we use objects with broad boundaries, the concept that absorbs all the uncertainty by which spatial data is commonly affected and allows computations in the presence of uncertainty without rough simplifications of the reality. The topological relations between objects with a broad boundary can be organized into a three-level concept hierarchy. We developed and implemented a method for an efficient determination of such topological relations. Based on the hierarchy of topological relations we present a method for mining spatial association rules for objects with uncertainty. The progressive refinement approach is used for the optimization of the mining process.     

Temperature-dependent electrical and dielectric properties of nematic liquid crystals doped with ferroelectric particles

We report on the temperature dependence of dielectric properties of nematic liquid crystals impregnated with BaTiO₃ (BTO) ferroelectric nanoparticles. The behavior of ion transport at low frequencies is discussed by means of dielectric spectroscopy, which allows the ionic concentration and the relaxation time of electrode polarization to be deduced. The experimental results imply that the ferroelectric nanoparticles can not only increase the traveling time of ions between two electrodes but also suppress the buildup of the electric double layers. Verified by the voltage holding ratio of cells containing various contents of BTO nanoparticles, it is obvious that doping BTO into liquid crystals is a low-cost and easy way to improve the device performance.     

Hyperstability and average hyperstability conditions for a broad class of gaussian stochastic systems

The author investigates the hyperstability problem for a broad class of single-control stochastic systems which may be considered as disturbed models of given deterministic systems. The stochasticity comes from the control, which is disturbed by an additive Gaussian noise with its own gain. Hyperstability conditions are given when the noise has a time-independent variance. When this variance depends explicitly upon the time, we define the time-average hyperstability, and conditions for average hyperstability are given. Similar problems are solved for multicontrol Gaussian systems. Illustrative examples show how one can derive from these results a broad class of absolute stability conditions.     

A microfluidic device for rapid concentration of particles in continuous flow by DC dielectrophoresis

This article presents a microfluidic device (so called concentrator) for rapid and efficient concentration of micro/nanoparticles using direct current dielectrophoresis (DC DEP) in continuous fluid flow. The concentrator is composed of a series of microchannels constructed with PDMS-insulating microstructures to focus efficiently the electric field in the flow direction to provide high field strength and gradient. Multiple trapping regions are formed within the concentrator. The location of particle trapping depends on the strength of the electric field applied. Under the experimental conditions, both streaming movement and DEP trapping of particles simultaneously take place within the concentrator at different regions. The former occurs upstream and is responsible for continuous transport of the particles, whereas the latter occurs downstream and rapidly traps the particles delivered from upstream. The observation agrees with the distribution of the simulated electric field and DEP force. The performance of the device is demonstrated by successfully and effectively concentrating fluorescent nanoparticles. At the sufficiently high electric field, the device demonstrates a trapping efficiency of 100%, which means downstream DEP traps and concentrates all (100%) the incoming particles from upstream. The trapping efficiency of the device is further studied by measuring the fluorescence intensity of concentrated particles in the channel. Typically, the fluorescence intensity becomes saturated in Trap 1 by applying the voltage (400 V) for >2 min, demonstrating that rapid concentration of the nanoparticles (10⁷ particles/ml) is achieved in the device. The microfluidic concentrator described can be implemented in applications where rapid concentration of targets is needed such as concentrating cells for sample preparation and concentrating molecular biomarkers for detection.     

仿生介入机器人的运动性能

针对弯曲多变的生物管腔,基于腹足动物运动机理,提出一种新型仿生介入机器人．通过理论建模及实验手段,分析管腔内壁表面特性、控制磁流变液固化的磁场强度、管腔蠕动、动压润滑膜减阻效果、直线电机运动方向变化频率对机器人运动性能的影响．结果表明：动压润滑膜能有效减小运动过程中的阻力;管壁内表面特性、控制磁流变液固化的磁场强度是影响机体与管道壁啮合效果的重要因素;直线电机运动方向的变化频率将影响机器人的运动性能;机器人能一定程度顺应管腔的自主或受迫小幅波动;当波动幅度较大时,机器人运动效率将大大降低.     

A method for solving the minimization of the maximum number of open stacks problem within a cutting process

In this paper, the problem of minimizing the maximum number of open stacks around a saw machine is addressed. A new heuristic and a branch-and-bound based exact method for the problem are presented. Computational tests comparing the new approach with other algorithms previously suggested in the literature were carried out.     

Analytical formulation of electric field and dielectrophoretic force for moving dielectrophoresis using Fourier series

Electrokinetics manipulation and separation of living cells employing microfluidic devices require good knowledge of the strength and distribution of electric field in such devices. AC dielectrophoresis is performed by generating non-uniform electric field using microsize electrodes. Among the several applications of dielectrophoretic phenomenon, this present study considers the recently introduced phenomenon of moving dielectrophoresis. An analytical solution using Fourier series is presented for the electric field distribution and dielectrophoretic force generated inside a microchannel. The potential at the upper part of the microchannel has been found by solving the governing equation of the electric potential with specific boundary conditions. The solutions for the electric field and dielectrophoretic force show excellent agreement with the numerical results. Microdevices were fabricated and experiments were carried out with living cells confirming and validating the analytical solutions.