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A major reason for infertility is due to male factors, including the quality of spermatozoa, which is a primary factor and often difficult to assess, particularly the total sperm concentration and its motile percentage. This work presents a simple microfluidic device to assess sperm quality by quantifying both total and motile sperm counts. The key design feature of the microfluidic device is two channels separated by a permeative phase-guide structure, where one channel is filled with raw semen and the other with pure buffer. The semen sample was allowed to reach equilibrium in both chambers, whereas non-motile sperms remained in the original channel, and roughly half of the motile sperms would swim across the phase-guide barrier into the buffer channel. Sperms in each channel agglomerated into pellets after centrifugation, with the corresponding area representing total and motile sperm concentrations. Total sperm concentration up to 10(8) sperms per ml and motile percentage in the range of 10-70% were tested, encompassing the cutoff value of 40% stated by World Health Organization standards. Results from patient samples show compact and robust pellets after centrifugation. Comparison of total sperm concentration between the microfluidic device and the Makler chamber reveal they agree within 5% and show strong correlation, with a coefficient of determination of R(2) = 0.97. Motile sperm count between the microfluidic device and the Makler chamber agrees within 5%, with a coefficient of determination of R(2) = 0.84. Comparison of results from the Makler Chamber, sperm quality analyzer, and the microfluidic device revealed that results from the microfluidic device agree well with the Makler chamber. The sperm microfluidic chip analyzes both total and motile sperm concentrations in one spin, is accurate and easy to use, and should enable sperm quality analysis with ease.

This paper addresses the gust response on the stator of a rotor/stator axial compressor, by decomposing the response into vortical and potential contributions. Experiments were conducted in a large-scale, low-speed compressor rig, with two axial gap cases — 10% and 30% chord — and at two time-mean loadings. To determine the gust response due to potential contribution, a two-step approach was taken. First, a panel code was used to determine the gust in the mid-gap plane for the rotor/stator configuration. Then, this calculated gust served as an inlet boundary of a Reynolds-averaged Navier-Stokes code for the stator cascade configuration. The vortical contributed gust response was found by subtracting the potential contributed response from the measured response. Results show that the vortical contributed response is largest near the instant when the rotor wake impinges at the stator leading edge. The potential contributed response reaches a maximum when the rotor trailing edge is axially upstream of the stator leading edge. The vortical contributed response dominates for all cases studied.Copyright © 1996 by ASME

We present a dielectrophoresis (DEP)-based cellular microarray chip for cell-based anticancer drug screening in perfusion microenvironments. Human breast cancer cells, MCF7, were seeded into the chip and patterned via DEP forces onto the planar interdigitated ring electrode (PIRE) arrays. Roughly, only one third of the cell amount was required for the chip compared to that for a 96-well plate control. Drug concentrations (cisplatin or docetaxel) were stably generated by functional integration of a concentration gradient generator (CGG) and an anti-crosstalk valve (ACV) to treat cells for 24 hours. Cell viability was quantified using a dual staining method. Results of cell patterning show substantial uniformity of patterned cells (92 ± 5 cells per PIRE). Furthermore, after 24 hour drug perfusion, no statistical significance in dose-responses between the chip and the 96-well plate controls was found. The IC(50) value from the chip also concurred with the values from the literature. Moreover, the perfusion culture exhibited reproducibility of drug responses of cells on different PIREs in the same chamber. The chip would enable applications where cells are of limited supply, and supplement microfluidic perfusion cultures for clinical practices.

Planar patch-clamp has revolutionized ion-channel measurement by eliminating laborious manipulation from the traditional micropipette approach and enabling high throughput. However, low yield in gigaseal formation and/or relatively high cost due to microfabricated processes are two main drawbacks. This paper presents patch clamping on glass substrate-an economical solution without sacrificing gigaseal yield rate. Two-stage CO(2) laser drilling methodology was used to generate an hourglass, funnel-like aperture of a specified diameter with smooth and debris-free surfaces on 150 microm borosilicate cover glass. For 1-3 microm apertures as patch-clamp chips, seal resistance was tested on human embryonic kidney, Chinese hamster ovary, and Jurkat T lymphoma cells with a gigaseal success rate of 62.5%, 43.6% and 66.7% respectively. Results also demonstrated both whole-cell and single channel recording on endogenously expressed ion channels to confirm the capability of different patch configurations.

Circulatory flow structures can be useful in a microfluidic device but often are difficult to generate mechanically in microscale. This paper presents generation of such flow via an in-plane resonating microplate (100×100×1.2μm3) actuated by Lorentz law. Results show either one of two nonlinear time-mean flow structures is feasible for the finite plate: (1) two-dimensional (2D) small-scale, counter-rotating microvortices or (2) three-dimensional, large-scale, recirculating flow. Sharpness of microplate’s edge is found to be the decisive factor for 2D microvortices to form. Both flow structures are robust and controllable. Potential applications include trapping and mixing of bioparticles in microfluidic devices.

Real life aerodynamics is time dependent by nature. For example, helicopter and gas turbine blades operate in the wakes of the previous blades, vortices can shed off the leading edge of a delta wing inducing velocities on the entire wing, and aerodynamic bodies may flutter causing very unsteady loading and unsteady shed vortex fields.

This work presents a simple process of reflow of melted glass by CO2 laser to form an hourglass-shaped aperture for cellular electrophysiological study. The fabricated aperture proves to be smooth, circular, debris-free, and freshly activated. Two-phase flow simulation illuminates details of the reflow process. The resulting seal resistance quality is well suited to measure ion-channel activities; a seal resistance of 1.9GΩ for PC-12 cell and a typical resistance of 200MΩ for Chinese hamster ovary cells were achieved. This approach can be integrated with microfluidics in a single cell patch or array configuration.

This work reports the design and testing of a prototype thermoacoustic refrigerator optimized by the code DeltaE. The key functional feature of this quarter‐wavelength resonator is its dual power input capability electric heating elements and the sun. These can be utilized independently or complimentarily to benefit all‐weather operation. The machine operates near 270 Hz with helium (60%)–argon (40%) mixture at two bars mean pressure. Heat from either heat source is transported from the high‐temperature end to the prime mover stack via thin copper plates that also serve as the hot‐end heat exchanger. Both stacks utilize an uncoated automobile catalytic converter ceramic structure with 1.3‐mm cell‐to‐cell square openings and 74% porosity. The ceramic structure provides a strong and easy‐to‐implement stack with minimal heat conduction. Both middle‐ and cold‐end heat exchangers use simple copper fin design, with the middle heat exchanger using circulating water cooling. DeltaE results predict a 30 °C temperature drop across the heat pump stack at no‐load condition with 30 W heating, 363 °C across the prime mover stack (work=4.0 W) and pressure fluctuation level equal to 6.2%. Results from the effects of working fluid, changing pressure, heating temperature, and cooling load will be discussed.

Unsteady pressure data are discussed for a 2-D Wortmann FX63-137 airfoil at Reynolds numbers 125,000 and 400,000, α = 0°, and over a range of reduced frequencies, k = ωc/2U ∞ from 0.15 to 6.4. Unsteady boundary layer data near the region of laminar separation are also presented for Re = 125,000, k = 0.15 and 2.0. Surface pressure data show that the unsteady excitation imposed interacts most actively in the transition region with large amplitude and higher harmonics. Unsteady boundary layer results in the region of laminar separation reveal that the time mean unsteady velocity profile for both reduced frequencies tested are quite similar. The ensemble averaged profiles for k = 0.15 suggest that the unsteady boundary layer tends to be more attached when the free stream velocity is minimum. Data show that this effect is less pronounced at k = 2.0.