Large scale dielectrophoretic construction of biofilms using textile technology

Arrays of microelectrodes for AC electrokinetic experiments were fabricated by weaving together stainless steel wires (weft) and flexible polyester yarn (warp) in a plain weave pattern. The cloth produced can be used to collect cells in low conductivity media by dielectrophoresis (DEP). The construction of model biofilms consisting of a yeast layer on top of a layer of M. luteus is demonstrated, using polyethylenimine (PEI) as the flocculating agent. This technique offers an alternative to the formation of biofilms at microelectrodes made by photolithography, and would allow the construction of biofilms with defined internal architectures by DEP at much larger scales than was possible previously. Furthermore, the flexibility of the cloth would also allow it to be distorted or folded into various shapes

Dielectrophoretic separation of cells using 3-D microelectrode

The dielectrophoretic (DEP) separation of cell, using microelectrodes structure, has been limited to small scale due to size of the substrate. This work was carried out to extend the capability of microelectrodes system by orientating the microelectrodes in three dimensions (3-D) for larger scale dielectrophoretic separation of microorganism. The designed 3-D separation chamber consists of microelectrodes on two opposing walls. Based on the FEMLAB simulation, the electric field was seen to be generated across the chamber, rather than between adjacent electrodes in the same plane like in the small scale system. This configuration led to a stronger electric field in the bulk medium. The experimental results showed that the 3-D microelectrodes chamber behaved similar to the system with microelectrodes on one wall. The effects of the main parameters such as voltage, frequency and flow rates were similar to that of the systems with all the electrodes on one wall, but on the overall, capture more cells. A gap size between 250 – 500 µm resulted in an electric field which is strong enough to hold cells while giving a reasonable cross sectional area at the same time. Although there is some improvement achieved by 3-D system, it is still not very much, as compared to the small scale system

Pengaruh Kompetensi Sumber Daya Manusia Terhadap Kinerja Karyawan PT.Bank Tabungan Negara, Tbk. Kantor Cabang Manado

. The purpose of this study was to analyze the influence of human resource competencies to employee performance at PT. Bank Tabungan Negara, Tbk. Branch Office Manado. The method used in this research is quantitative method by using correlation and regression analysis. The analysis showed that the competence of human resources have a significant effect on the performance of employees, as well as the regression coefficient of human resource competencies which meant that if the competence of human resources increased by one scale, the performance of employees will be increased by zero point nine one assuming factor other Factors unchanged. Thus, human resources competencies at PT. Bank Tabungan Negara Branch Manado make a positive contribution to the performance of the employee

Factors affecting dielectrophoretic separation of cells using high gradient electric field strength system

An investigation on dielectrophoretic separation of cells has been conducted using high-gradient electric field system (HGES). The HGES system consisted of two concentric cylindrical electrodes whereby the space between them was filled with glass beads. The glass beads were found to distort the electric field generated between the two electrodes and thus creating a high field gradient sites that produce dielectrophoretic force for cells collection. In order to study the effectiveness of the system in separating the cells, a series of experiments have been conducted. Here, yeast cells were introduced into the system and the number of cells collected was measured. The effects of voltage, flow rate, type of matrix, height of matrix and sample concentration have been investigated. In addition, the electric field analysis for the HGES has also been carried out using FEMLAB. Results show that the cells collection is influenced by the effect at the condition with and without electric field. Further analysis on the investigating factors enabled one to predict optimum values for voltage, flow rate, type of matrix, and height of matrix and sample concentration in order to improve the efficiency of the system by reducing the effect when no field is applied

Enhanced dielectrophoresis of nanocolloids by dimer formation

We investigate the dielectrophoretic motion of charge-neutral, polarizable nanocolloids through molecular dynamics simulations. Comparison to analytical results derived for continuum systems shows that the discrete charge distributions on the nanocolloids have a significant impact on their coupling to the external field. Aggregation of nanocolloids leads to enhanced dielectrophoretic transport, provided that increase in the dipole moment upon aggregation can overcome the related increase in friction. The dimer orientation and the exact structure of the nanocolloid charge distribution are shown to be important in the enhanced transport

Colloidal particles at a nematic-isotropic interface: effects of confinement

When captured by a flat nematic-isotropic interface, colloidal particles can be dragged by it. As a result spatially periodic structures may appear, with the period depending on a particle mass, size, and interface velocity~\cite{west.jl:2002}. If liquid crystal is sandwiched between two substrates, the interface takes a wedge-like shape, accommodating the interface-substrate contact angle and minimizing the director distortions on its nematic side. Correspondingly, particles move along complex trajectories: they are first captured by the interface and then `glide' towards its vertex point. Our experiments quantify this scenario, and numerical minimization of the Landau-de Gennes free energy allow for a qualitative description of the interfacial structure and the drag force.Comment: 7 pages, 9 figure

Dielectrophoresis of nanocolloids: a molecular dynamics study

Dielectrophoresis (DEP), the motion of polarizable particles in non-uniform electric fields, has become an important tool for the transport, separation, and characterization of microparticles in biomedical and nanoelectronics research. In this article we present, to our knowledge, the first molecular dynamics simulations of DEP of nanometer-sized colloidal particles. We introduce a simplified model for polarizable nanoparticles, consisting of a large charged macroion and oppositely charged microions, in an explicit solvent. The model is then used to study DEP motion of the particle at different combinations of temperature and electric field strength. In accord with linear response theory, the particle drift velocities are shown to be proportional to the DEP force. Analysis of the colloid DEP mobility shows a clear time dependence, demonstrating the variation of friction under non-equilibrium. The time dependence of the mobility further results in an apparent weak variation of the DEP displacements with temperature