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An adhesion-based cell-separation device is developed for the extraction of rare cells from a cell mixture. The cell-separation principle mimics leukocyte recruitment from blood vessels in our body, where leukocytes are decelerated by antigen-antibody interaction at the sites of inflammation or injury. Separation of cell mixture can be accomplished by simply introducing the sample plug through an antibody-immobilized microchannel without any pre- or postprocessing. A new class of amino-functionalized parylene (diX AM) is employed in order to provide amino group on the channel-wall surface. The amount of immobilized biomolecules on diX AM surface is characterized through quartz-crystal-microbalance measurements. The number density of immobilized biotin is as large as [10.sup.1] [m.sup.-2], which indicates an amount of amino group enough to immobilize biotin and other biomolecules in a closely packed state. It is shown by the measurement of cell velocity in the CD31-coated diX AM microchannel that the flowing velocity of human endothelial cells are reduced by up to 70% due to specific adhesion of CD31 antigens and antibodies. The results are further analyzed by using a 2-D membrane-peeling model, with which the cell velocity can be estimated under different conditions of antibody number density and bulk mean velocity. Based on the experimental results, a cell-separation device for treating a 1-[micro]L cell-mixture plug is designed and microfabricated. A mixture of human endothelial cells and leukocytes is successfully separated into plugs of each cell type within a shorter period of time as compared to conventional cell-separation methods which require sample preprocessing. [2007-0258] Index Terms--Antigen-antibody interaction, cell separation, functionalized parylene, regenerative medicine.

We have established methods for the design and fabrication of a novel MEMS actuator for flow control based on the electrostrictive principle. Patterned metal electrodes were employed in order to obtain large out-of-plane deformation. A series of finite-element method (FEM) analyses of the electrical and strain fields was performed in order to optimize the design parameters. The maximum deformation for 2-mm-diameter actuators reaches 112 [micro]m, which is 5.6% of the actuator diameter and six times larger than that of the plain metal-electrode actuator. The elastic energy density reaches 29% of the stored electrostatic energy. The power consumption at the driving frequency of 100 Hz is estimated to be on the order of 100 [micro]W. The present electrostrictive actuator has a fast response, and its operating frequency is up to several kilohertz. A synthetic jet issuing from a 0.4-mm orifice is successfully developed using the present electrostrictive actuator, and this demonstrates the viability of the present actuator in active flow control. [2006-1762] Index Terms--Electrostrictive polymer, finite-element method (FEM) analysis, out-of-plane deformation, patterned metal electrode, synthetic jet.

Hybrid systems, which are based on a micro gas turbine ([micro]GT) and a solid oxide fuel cell (SOFC), are expected to achieve much higher efficiency than traditional [micro]GT's. In this paper, the effects of cycle design parameters on the performance and feasibility of a [micro]GT-SOFC hybrid system of 30 kW power output are investigated. It is confirmed that the hybrid system is much superior to a recuperated gas turbine in terms of its power generation efficiency and aptitude for small distributed generation. General design strategy is found that less direct fuel input to a combustor as well as higher recuperator effectiveness leads to higher generation efficiency, while higher steam-carbon ratio moderates requirements for the material strength. The best possible conceptual design of a 30-kW [micro]GT-SOFC hybrid system is shown to give power generation efficiency over 65% (lower heating value). [DOI: 10.1115/1.1787505]

An efficient magnetic force driven mixer with simple configuration is designed, fabricated, and tested. It is designed to facilitate the mixing of magnetic beads and biomolecules in a microchannel, where mixing is unavoidably inefficient due to its low Reynolds number. With appropriate temporal variations of the force field, chaotic mixing is achieved, hence the mixing becomes effective. The mixing device consists of embedded microconductors as a magnetic field source and a microchannel that guides the streams of working fluid. It is demonstrated that a pair of integrated micro conductors provides a local magnetic field strong enough to attract nearby magnetic beads. Mixing of magnetic beads is accomplished by applying a time-dependent control signal to a row of conductors, at the Reynolds number of as low as [10.sup.-2]. Two-dimensional numerical simulation has been performed to design the configuration of the channel and electrodes, which creates chaotic motion of beads. It is found that a simple two-dimensional serpentine channel geometry with the transverse electrodes is able to create the stretching and folding off material lines, which is a manifestation of chaos. The mixing pattern predicted by the simulation has been confirmed by both flow visualization and PTV (Particle Tracking Velocimetry) in the chaotic mixer fabricated, which should greatly increase the attachment of beads onto the target biomolecules. The optimum frequency of applied control signal is searched by evaluating the Lyapunov exponent in both numerical and experimental particle tracking. It is found that the range of optimum Strouhal number is 5 < St < 12, which is defined by the channel width and the mean velocity. [1200] Index Terms--Bio MEMS, cell sorting, chaotic mixing, magnetic beads, magnetic force, micro fluidic system.

A direct numerical simulation of the completely developed turbulent channel flow and heat transfer with uniform wall injection and suction shows that the friction coefficient is decreased by the injection, but it tends to stimulate the near-wall turbulence activity so that the Reynolds stresses and turbulent heat fluxes are increased, whereas the suction has an inverse affect.

Three-dimensional particle tracking velocimetry helps measure stabilities of all three velocity components and analyze the structure of a turbulent flow field above a riblet surface. A drag-reducing condition decreases turbulent velocity fluctuations and Reynolds shear stress near riblet surface, and also suppresses the redistribution mechanism above riblet surface. A cross-stream secondary flow close to the rib under neutral drag increases turbulent momentum transport and drag-reducing effect of the riblet.

The effects of oblique angles and wavy walls on heat transfer and pressure loss are investigated in modeled counterflow recuperators. Results showed that the wavy walls produced counter-rotating streamwise vortices, which drastically modified the flow field due to intense secondary flow, and significant enhancement of heat transfer can be achieved by using optimum set of oblique angles and wave amplitude with comparatively less pressure loss.