Search

Moving dielectrophoresis has been recently developed by the authors as an alternative method to achieve simultaneous cell fractionation and transportation. With an array of independently excitable microelectrodes, this method generates a moving electric field to sequentially fractionate and transport cells across a microchannel. Due to the peculiarity of this method, the motion of the cells is unsteady and there are interesting and distinct differences between cells experiencing positive or negative dielectrophoresis. For a proper understanding and design of a microdevice utilizing this methodology, this study presents a model for the equation of motion for a polarized cell and its unsteady motion under moving dielectrophoresis. The model considers the basic module to generate a moving electric field, where there is a finite-width top electrode and an infinite-width bottom electrode, in a parallel-plate configuration. The forces considered include dielectrophoretic force, fluid drag, buoyancy, and gravitational force. These forces are modeled as equivalent point forces acting at the center of mass of the cell. A parallel-plate wall correction factor is employed to account for the effect of the large cell size to microchannel height ratio. Various parameters are examined including the initial position of the cell relative to the electrodes, cell's Clausius--Mossotti factor, cell size, applied voltage, electrode width, interelectrode gap, microchannel height, number of energized electrodes, and types of electrode configurations. Reasonable agreements were obtained between simulated and experimental results. As the solution of the unsteady motion is rather tedious, a MATIAB algorithm, with all the associated files, for the prediction of the cell trajectory, is available on request.

This study presents a new cell manipulation method using a moving dielectrophoretic force to transport or fractionate cells along a microfluidic channel. The proposed moving dielectrophoresis (mDEP) is generated by sequentially energizing a single electrode or an array of electrodes to form an electric field that moves cells continuously along the microchannel. Cell fractionation is controlled by the applied electrical frequency, and cell transportation is controlled by the interelectrode activation time. The applicability of this method was demonstrated to simultaneously fractionate and transport Saccharomyces cerevisiae yeast cells, both viable and nonviable, by operating at conditions under which the cells were subjected to positive and negative dielectrophoresis, respectively. Compared to the conventional dielectrophoresis (cDEP and traveling wave dielectrophoresis (twDEP), moving dielectrophoresis allows cells to be separated on the basis of the real part of the Clausius-Mossotti factor, as in cDEP, but yet allows the direct transportation of separated cells without using fluid flow, as in twDEP. This dielectrophoresis technique provides a new way to manipulate cells and can be readily implemented on programmable multielectrode devices.

This article proposes an algorithm to design an integrated control chart system consisting of several individual control charts, each of which is used to monitor a critical process stage in the manufacture of a product. The design algorithm considers all the charts within a system in an integrative and optimal manner. Consequently, the performance characteristics of the system as a whole can be significantly improved and the product quality will be further enhanced. Such an improvement is achieved without requiring additional cost and effort for on-line inspections. Furthermore, the floor operators can utilize and understand the optimal control chart system as easily as they do the existing system. Some useful guidelines have also been highlighted to aid the users to adjust the control limits of the control charts in a system., 1. Introduction The fabrication of a product usually includes many process stages. The integration of all these stages results in a manufacturing system. Specifically, in the manufacture of a mechanical [...]

This research work proposes algorithms for the optimization design of an integrated control chart system monitoring a multi-stage and multi-stream manufacturing system. The optimization design is carried out under resource constraints, such as operators equipped with measuring instruments. The effectiveness of the chart system is improved and the product quality is enhanced with minimum additional cost and effort. Furthermore, the optimal control chart system can be utilized and understood by shop floor operators as easily as the traditional system. Useful guidelines are established to aid the users to adjust the sample sizes, sampling intervals and control limits of the control charts in a system. The proposed algorithms are illustrated through an example. [ABSTRACT FROM AUTHOR]