Immobilization of cells inside microfluidic devices is a promising approach for enabling studies related to drug screening and cell biology. Despite extensive studies in using grooved substrates for immobilizing cells inside channels, a systematic study of the effects of various parameters that influence cell docking and retention within grooved substrates has not been performed. We demonstrate using computational simulations that the fluid dynamic environment within microgrooves significantly varies with groove width, generating microcirculation areas in smaller microgrooves. Wall shear stress simulation predicted that shear stresses were in the opposite direction in smaller grooves (25 and 50 microm wide) in comparison to those in wider grooves (75 and 100 microm wide). To validate the simulations, cells were seeded within microfluidic devices, where microgrooves of different widths were aligned perpendicularly to the direction of the flow. Experimental results showed that, as predicted, the inversion of the local direction of shear stress within the smaller grooves resulted in alignment of cells on two opposite sides of the grooves under the same flow conditions. Also, the amplitude of shear stress within microgrooved channels significantly influenced cell retainment in the channels. Therefore, our studies suggest that microscale shear stresses greatly influence cellular docking, immobilization, and retention in fluidic systems and should be considered for the design of cell-based microdevices.

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Microcirculation within grooved substrates regulates cell positioning and cell docking inside microfluidic channels

Present and future of rapid and/or high-throughput methods for nucleic acid testing.

Metal cutting generates heat which influences the quality of a finished product, the force needed in cutting as well as limiting the life of the cutting tool. There are various attempts by researchers all over the world to understand the mechanism and theory behind the temperature built-up during machining in order to achieve optimized machining procedure and best workpiece results. Theories are developed, experiments conducted as well as models and simulations proposed. The latest attempt in metal cutting cooling is through the use of chilled air, cryogenic cooling. A Ranque-Hilsch vortex tube (RHVT), a device with no moving parts, is used for this low-cost refrigeration purpose. Backgrounds of RHVT, various studies conducted on it, its performance and applications are discussed for the high speed metal cutting cooling application for mold and die steels. Option for future research is proposed.

	 

	Key words: High speed machining, end milling, cryogenic cooling, vortex tube, mold and die.

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A review of cryogenic cooling in high speed machining (HSM) of mold and die steels

A thermocycler apparatus and method for rapidly performing the PCR process employs at least two thermoelectric modules which are in substantial spatial opposition with an interior space present between opposing modules. One or multiple sample vessels are placed in between the modules such that the vessels are subjected to temperature cycling by the modules. The sample vessels have a minimal internal dimension that is substantially perpendicular to the modules that facilitates rapid temperature cycling. In embodiments of the invention the sample vessels may be deformable between: a) a shape having a wide mouth to facilitate filling and removing of sample fluids from the vessel, and b) a shape which is thinner for conforming to the sample cavity or interior space between the thermoelectric modules of the thermocycler for more rapid heat transfer.

Thermocycler and sample vessel for rapid amplification of dna

Numerical Investigation of Vortex Tube Refrigerator with a Divergent Hot Tube

An innovative polymerase chain reaction (PCR) thermocycler capable of performing real-time optical detection is described below. This device utilizes the Ranque–Hilsch vortex tube in a system to efficiently and rapidly cycle three 20 μL samples between the denaturation, annealing, and elongation temperatures. The reaction progress is displayed real-time by measuring the size of a fluorescent signal emitted by SYBR green/double-stranded DNA complexes. This device can produce significant reaction yields with very small amounts of initial DNA, for example, it can amplify 0.25 fg (∼5 copies) of a 96 bp bacteriophage λ-DNA fragment 2.7×1011-fold by performing 45 cycles in less than 12 min. The optical threshold (150% of the baseline intensity) was passed 8 min into the reaction at cycle 34. Besides direct applications, the speed and sensitivity of this device enables it to be used as a scientific instrument for basic studies such as PCR assembly and polymerase kinetics.

/pdf/ranque-hilsch-vortex-tube-thermocycler-for-fast-dna-3g96k5c5g9.pdf

Ranque-Hilsch vortex tube thermocycler for fast DNA amplification and real-time optical detection

A thermal cycling apparatus (10) utilizes hot and cold gas streams produced from pressurized gas being passed through a Ranque-Hilsch Vortex Tube (20) to efficiently and rapidly cycle samples (70) (i.e., DNA+Primer+Polymerse) between the denaturation, annealing, and elongation temperatures of the PCR process. The samples (70) are disposed within a reaction chamber (40) that, through connection with a vortex tube (20), allows the gas to contact the samples (70). The temperature of the gas that is allowed to contact the samples (70) is controlled by a valving system (30) being connected with the vortex tube (20) and the reaction chamber (40). The valving system (30) controls the flow of cold gas into the reaction chamber (40) where it is mixed with the hot gas to establish the different temperatures required for the denaturation, annealing, and elongation steps of the cycle.

Vortex tube thermocycler

An innovative polymerase chain reaction (PCR) thermocycler using pressurized gas through a Ranque–Hilsch vortex tube is described below. This device can amplify 10 pg of 186 bp Escherichia coli uidA amplicon in a 20 µL sample 3.3 × 108‐fold, by performing 35 cycles in less than 8 min. This PCR amplification corresponds to an overall efficiency of 75%.

Ranque–Hilsch Vortex Tube Thermocycler for DNA Amplification

/pdf/ranque-hilsch-vortex-tube-thermocycler-for-fast-dna-3kp278hpd8.pdf

Ranque–Hilsch vortex tube thermocycler for fast DNA amplification and real-time optical detection

In this article, experimental and numerical analyses to investigate the thermal control of an innovative vortex tube based polymerase chain reaction (VT-PCR) thermocycler are described. VT-PCR is capable of rapid DNA amplification and real-time optical detection. The device rapidly cycles six 20μl 96bp λ-DNA samples between the PCR stages (denaturation, annealing, and elongation) for 30cycles in approximately 6min. Two-dimensional numerical simulations have been carried out using computational fluid dynamics (CFD) software FLUENT v.6.2.16. Experiments and CFD simulations have been carried out to measure/predict the temperature variation between the samples and within each sample. Heat transfer rate (primarily dictated by the temperature differences between the samples and the external air heating or cooling them) governs the temperature distribution between and within the samples. Temperature variation between and within the samples during the denaturation stage has been quite uniform (maximum variation a...

/pdf/thermal-analysis-of-the-vortex-tube-based-thermocycler-for-m6b2sowy12.pdf

Ryan J. Ebmeier

Papers

Ranque-Hilsch vortex tube thermocycler for fast DNA amplification and real-time optical detection

Vortex tube thermocycler

Ranque–Hilsch Vortex Tube Thermocycler for DNA Amplification

Ranque–Hilsch vortex tube thermocycler for fast DNA amplification and real-time optical detection

Thermal analysis of the vortex tube based thermocycler for fast DNA amplification: Experimental and two-dimensional numerical results