Glass Channel Research Articles

微細矩形流路内における気液二相流動様相観察と振動の及ぼす影響

In this study, we performed to observe horizontal vapor-liquid two phase flow of refrigerant R 134a in the rectangular glass channel which hydraulic diameter is 0.84 mm. The test glass tube was added the oscillation to the gravity direction for slug and stratified flow under low mass flux and heat flux. When the channel was oscillated of certain frequency and amplitude, the liquid of the corner part of rectangular channel waved up and down. In slug flow, dry surface of central was supplied the liquid by the oscillation and was formed the thin liquid. In stratified flow, dry surface of top was supplied the liquid and flow pattern changed to annular from stratified flow. The oscillation influences were investigated in a quantitative way.

Translocation of fluoranthene in porous media by advancing and receding air–water interfaces

Abstract Polycyclic aromatic hydrocarbons (PAH) generally have low water solubility and high octanol–water partition coefficients. In soils and sediments, PAH tend to partition to organic matter and mineral phases, and are, therefore, relatively immobile. However, moving air–water interfaces may scour PAH from solid phases and translocate PAH. The objective of our study was to assess the effect of moving air–water interfaces on the transport of fluoranthene, a four-ring PAH, in unsaturated porous media. A glass channel (i.d. 3.7 mm × 7.5 cm) packed with fluoranthene-contaminated glass beads (dia. 0.5 mm) was used as porous medium. Fluoranthene was initially present as species sorbed to the glass beads and as particulates precipitated out from solution. Capillary fringe fluctuations were simulated by repeatedly imbibing and draining the medium with water. Fluoranthene translocation was visualized by confocal microscopy and quantified by image analysis. Results showed that the first two cycles of capillary fringe fluctuations were the most effective in translocating fluoranthene; 25–50% of fluoranthene surface coverage was translocated from the glass channel. During imbibition, fluoranthene particles were detached from the solid surface, and attached to the advancing air–water interface. During drainage, fluoranthene was removed from the solid–liquid interface with the receding air–water interface. Repeated imbibition and drainage cycles, causing air–water interfaces to move through the porous medium, can be useful method to remove PAH from contaminated soils and sediments.

On-Chip Pressure Generation for Driving Liquid Phase Separations in Nanochannels.

In this Article, we describe the generation of pressure gradients on-chip for driving liquid phase separations in submicrometer deep channels. The reported pressure-generation capability was realized by applying an electrical voltage across the interface of two glass channel segments with different depths. A mismatch in the electroosmotic flow rate at this junction led to the generation of pressure-driven flow in our device, a fraction of which was then directed to an analysis channel to carry out the desired separation. Experiments showed the reported strategy to be particularly conducive for miniaturization of pressure-driven separations yielding flow velocities in the separation channel that were nearly unaffected upon scaling down the depth of the entire fluidic network. Moreover, the small dead volume in our system allowed for high dynamic control over this pressure gradient, which otherwise was challenging to accomplish during the sample injection process using external pumps. Pressure-driven velocities up to 3.1 mm/s were realized in separation ducts as shallow as 300 nm using our current design for a maximum applied voltage of 3 kV. The functionality of this integrated device was demonstrated by implementing a pressure-driven ion chromatographic analysis that relied on analyte interaction with the nanochannel surface charges to yield a nonuniform solute concentration across the channel depth. Upon coupling such analyte distribution to the parabolic pressure-driven flow profile in the separation duct, a mixture of amino acids could be resolved. The reported assay yielded a higher separation resolution compared to its electrically driven counterpart in which sample migration was realized using electroosmosis/electrophoresis.

Porous glass as reactor for preparation of bismuth nanoparticles

Synthesis of bismuth nanoparticles in the interpenetrating channels of porous glass limiting the size of the obtained particles includes the stages of anchoring the insoluble bismuth oxide inside the glass, the oxide reduction with glycerol, and release of the metal nanoparticles from the pores volume. Hexagonal crystallites have been found in the sub-micron powder of bismuth along with its stable rhombohedral form. The prepared powders exhibited the reduced temperature and enthalpy of melting.

Self-Guided Supramolecular Cargo-Loaded Nanomotors with Chemotactic Behavior towards Cells.

Delivery vehicles that are able to actively seek and precisely locate targeted tissues using concentration gradients of signaling molecules have hardly been explored. The directed movement toward specific cell types of cargo-loaded polymeric nanomotors along a hydrogen peroxide concentration gradient (chemotaxis) is reported. Through self-assembly, bowl-shaped poly(ethylene glycol)-b-polystyrene nanomotors, or stomatocytes, were formed with platinum nanoparticles entrapped in the cavity while a model drug was encapsulated in the inner compartment. Directional movement of the stomatocytes in the presence of a fuel gradient (chemotaxis) was first demonstrated in both static and dynamic systems using glass channels and a microfluidic flow. The highly efficient response of these motors was subsequently shown by their directional and autonomous movement towards hydrogen peroxide secreting neutrophil cells.

Self‐Guided Supramolecular Cargo‐Loaded Nanomotors with Chemotactic Behavior towards Cells

AbstractDelivery vehicles that are able to actively seek and precisely locate targeted tissues using concentration gradients of signaling molecules have hardly been explored. The directed movement toward specific cell types of cargo‐loaded polymeric nanomotors along a hydrogen peroxide concentration gradient (chemotaxis) is reported. Through self‐assembly, bowl‐shaped poly(ethylene glycol)‐b‐polystyrene nanomotors, or stomatocytes, were formed with platinum nanoparticles entrapped in the cavity while a model drug was encapsulated in the inner compartment. Directional movement of the stomatocytes in the presence of a fuel gradient (chemotaxis) was first demonstrated in both static and dynamic systems using glass channels and a microfluidic flow. The highly efficient response of these motors was subsequently shown by their directional and autonomous movement towards hydrogen peroxide secreting neutrophil cells.

Implementation of a shadow mask for direct writing in abrasive jet micro-machining

Abrasive jet micromachining uses a jet of high-speed particles to erode a wide variety of materials. Since the air driven jet is highly divergent, the edges of the desired features are usually defined using a mask which is attached to the surface of the target material. This paper presents an alternate technique using shadow masks that can be moved over the surface, thus allowing direct writing of features on the surface. This eliminates the additional cost and time of fabricating and attaching traditional masks. The technique was used to machine straight channels in borosilicate glass, and their quality was compared to those machined using traditional clamped masks. The channels machined using the shadow mask were found to be approximately 10% wider than those machined using clamped masks up to an aspect ratio of approximately 0.5. Under these conditions, the shadow mask channels were bounded on the edges by lightly-eroded, frosted regions approximately 60μm wide. The effects of nozzle standoff, shadow mask standoff, particle size and mask thickness on the frosted regions and the channel width were studied. To create a direct-writing device, a crossed arrangement of two mutually perpendicular sets of shadow masks was used to generate arbitrarily curved paths. These crossed shadow masks resulted in less frosting than did the parallel masks.

Automation Highlights from the Literature

Automation Highlights from the Literature

The Role of Contact Line (Pinning) Forces on Bubble Blockage in Microchannels.

This paper highlights the influence of contact line (pinning) forces on the mobility of dry bubbles in microchannels. Bubbles moving at velocities less than the dewetting velocity of liquid on the surface are essentially dry, meaning that there is no thin liquid film around the bubbles. For these "dry" bubbles, contact line forces and a possible capillary pressure gradient induced by pinning act on the bubbles and resist motion. Without sufficient driving force (e.g., external pressure), a dry bubble is brought to stagnation. For the first time, a bipartite theoretical model that estimates the required pressure difference across the length of stagnant bubbles with concave and convex back interfaces to overcome the contact line forces and stimulate motion is proposed. To validate our theory, the pressure required to move a single dry bubble in square microchannels exhibiting contact angle hysteresis has been measured. The working fluid was deionized water. The experiments have been conducted on coated glass channels with different surface hydrophilicities that resulted in concave and convex back interfaces for the bubbles. The experimental results were in agreement with the model's predictions for square channels. The predictions of the concave and convex back models were within 19% and 27% of the experimental measurements, respectively.

Electrophoretic extraction of low molecular weight cationic analytes from sodium dodecyl sulfate containing sample matrices for their direct electrospray ionization mass spectrometry.

While the use of sodium dodecyl sulfate (SDS) in separation buffers allows efficient analysis of complex mixtures, its presence in the sample matrix is known to severely interfere with the mass-spectrometric characterization of analyte molecules. In this article, we report a microfluidic device that addresses this analytical challenge by enabling inline electrospray ionization mass spectrometry (ESI-MS) of low molecular weight cationic samples prepared in SDS containing matrices. The functionality of this device relies on the continuous extraction of analyte molecules into an SDS-free solvent stream based on the free-flow zone electrophoresis (FFZE) technique prior to their ESI-MS analysis. The reported extraction was accomplished in our current work in a glass channel with microelectrodes fabricated along its sidewalls to realize the desired electric field. Our experiments show that a key challenge to successfully operating such a device is to suppress the electroosmotically driven fluid circulations generated in its extraction channel that otherwise tend to vigorously mix the liquid streams flowing through this duct. A new coating medium, N-(2-triethoxysilylpropyl) formamide, recently demonstrated by our laboratory to nearly eliminate electroosmotic flow in glass microchannels was employed to address this issue. Applying this surface modifier, we were able to efficiently extract two different peptides, human angiotensin I and MRFA, individually from an SDS containing matrix using the FFZE method and detect them at concentrations down to 3.7 and 6.3 μg/mL, respectively, in samples containing as much as 10 mM SDS. Notice that in addition to greatly reducing the amount of SDS entering the MS instrument, the reported approach allows rapid solvent exchange for facilitating efficient analyte ionization desired in ESI-MS analysis.

Nd^3+-doped ion-exchanged aluminum germanate glass channel waveguide

K+–Na+ ion-exchanged channel waveguide has been fabricated in Nd3+ doped aluminum germanate (NMAG) glasses with potential photosensitive property. The channel waveguide exhibits single mode at 1.3μm and the mode field diameters were measured to be horizontally 10.1μm and vertically 5.3μm, respectively. Amplified spontaneous emissions (ASE) of 905, 1060, 1334 and 1816nm originating from the 4F3/2 level were recorded under ~800nm diode laser pumping and the maximum stimulated emission cross-sections for the 4F3/2→4I11/2 and 4F3/2→4I13/2 transitions are derived to be 21.5 × 10−21 and 7.6 × 10−21cm2, respectively. In addition, with 71.8% quantum efficiency and the largest emission intensity among various Nd3+ doping cases, 2wt% Nd2O3 is considered as the optimized doping concentration for the compact channel waveguide. The ion-exchanged Nd3+-doped NMAG glass channel waveguides offer favorable prospects for the development of optical waveguide amplifiers, broadband light sources and infrared UV-written grating waveguide lasers.

On-Line Preconcentrator on a Glass Capillary with Electrokinetic Trapping Technique

In proteomics, the needs for concentrating the low-abundant molecules from the target samples are rapidly increased, since the concentration of low abundant ones might fall below the detection limit of biosensors.1 In many cases, the samples are needed with several separation steps so that the preconcentration step is even more important when using microfluidic sensing systems.Recently, protein preconcentrator are intensively investigated with micro/nanofluidic channel networks.2 , 3 More recently, the microfluidic chips with perm-selective ion nanoporous material have been developed for enhancing their performance4. The microfluidic preconcentrator based on electrokinetic trapping technique was intensively studied with PDMS, however, the surface of PDMS is unstable, which lead to inefficient use of electrokinetic trapping. Here, we suggest the capillary based preconcentrator for collecting target proteins. It is well-known that the capillary has well-defined surfaces and could be connected easily with other analytical equipment. For this, we developed preconcentrator on a glass capillary simply by coating the ion-permslective membrane inside the glass channels. For operating protein preconcentration, we applied 20 V at both side electrodes in reservoir and tested the negative pressures to operate the ICP, then observed ion concentration polarization formed around ion permselective nanoporous material pattern. We tested the BDNF protein directly connected from the inserting tube in a mouse and measured real-time BDNF protein quantities with times This simple and powerful method can provide a high sensitivity and a high reliability for preconcentration of other analysis equipment such as electro-spray components for the Mass Spec applications.

The effect of temperature on the cryogenic abrasive jet micro-machining of polytetrafluoroethylene, high carbon steel and polydimethylsiloxane

A previously developed cryogenic abrasive jet micro-machining apparatus was used to machine polytetrafluoroethylene (PTFE), high carbon steel, and polydimethylsiloxane (PDMS) at temperatures between −182°C and 17°C. As the machining temperature was lowered, the maximum erosion rate of PTFE increased five-fold and was found to occur at progressively higher angles of attack, shifting from 15° to 90°, although the angular dependence weakened and the maximum became less pronounced. This was similar to the behavior of PDMS observed in an earlier study [1]. The dependence of the erosion rate on angle of attack in high carbon steel, a useful masking material, was found to be insensitive to temperature, but the erosion rate increased approximately two-fold as the temperature decreased from 17°C to −182°C. The cross-sectional profiles of masked, machined micro-channels in PDMS and PTFE had relatively steep sidewalls compared to glass channels, even at the lowest temperature of −182°C, which indicates erosion was still not fully brittle. Predictions of the evolution of the channel cross-sectional profiles generally agreed well with experiments, although the channel width in PDMS at −182°C was under-predicted, most likely due to thermal effects. None of the materials exhibited an erosion incubation period, and there was minimal particle embedding in the samples machined below room temperature.

Micro-object manipulation in a microfabricated channel using an electromagnetically driven microrobot with an acoustically oscillating bubble

This paper presents an untethered microrobot swimming in human blood vessels through electromagnetic actuation to manipulate bio/micro-objects using an acoustically oscillating bubble attached to the microrobot as a grasping tool. First, for the three-dimensional (3D) actuation of the microrobot in arbitrarily shaped blood vessels, an electromagnetic system consisting of horizontal and vertical pairs of Helmholtz and Maxwell electric coils is designed and manufactured, and the magnetic flux density generated from the designed system is verified with theory. Using the developed electromagnetic system, the actuation of a spherical microrobot (800μm dia.) made of a cylindrical neodymium magnet covered with clay is successfully demonstrated in X–Y and X–Z planes along with a T-shaped glass channel. Second, micro-object manipulation using an acoustically oscillating bubble is separately investigated. When a bubble is acoustically excited by a piezoactuator around its natural frequency, it oscillates and simultaneously generates microstreaming and secondary radiation force, which can be used to capture a neighboring object. The capturing distance of an acoustically oscillating bubble (550μm dia.) and its oscillation amplitude in different frequencies and voltages are measured by using a fish egg (1mm dia.) and high-speed camera, respectively. The capturing distance is proportional to the bubble oscillation amplitude. The maximum capturing distance and bubble oscillation amplitude (ɛ=Δ/D) at its natural frequency (11kHz) and 250Vrms are approximately 2.3mm and 0.13, respectively. Finally, as a proof of concept, the manipulation of a fish egg (800μm dia.) in a microfabricated channel with tandem rectangular hills is experimentally achieved by the electromagnetically driven microrobot incorporated with an acoustically oscillating bubble.

The influence of flow rate on inter-nucleation site heat transport

The main topic of this paper is the influence of vertically aligned nucleation sites on each other in upward flow boiling. A setup was constructed to facilitate vertical up-flow of deminiralized water under saturation conditions. The main test section is a glass channel with a set of vertically aligned bubble generators. Each bubble generator is operated independently, where power and wall temperature are registered and the vapour bubbles are visualized by a high-speed camera. During the experiments, the downstream bubble generator (BG1) power is kept constant, while the power fed to the upstream bubble generator (BG2) is incrementally increased. Two main trends have been identified. The first trend is dominated by added convection from one site to the other. Both bubble frequency and detachment diameter on BG1 increase with increased power fed to upstream BG2. This effect decreases with increasing inter-site distance and becomes more significant with increasing liquid flow rate. When vapor bubbles start nucleating from BG2, these vapor bubbles inhibit bubble nucleation BG1 and can even lead to deactivation of this nucleation site. This second trend is only weakly dependent on inter-site distance, since the inhibition originates from bubbles flowing past BG1 in close proximity.

Characterisation of Micro Channels in Electrochemical Discharge Machining Process

Micromachining techniques has increased the demand for precise and accurate instruments which are used in many industries. Glass materials offer higher challenges in micro machining as they are tough, non-conducting and difficult to machine with conventional machining operations. Electro Chemical Discharge Machining (ECDM) is a new non-conventional hybrid machining process which combines the features of Electrical Discharge Machining (EDM) and Electro Chemical Machining (ECM) to machine both conducting and nonconducting materials. In the present paper effect of various process parameters like voltage, concentration of electrolyte, duty factor and temperature on ECDM process are studied to obtain desired micro channels in soda lime glass. Design of Experiment (DOE) is used to plan and conduct the experiments. The Response Surface Modelling (RSM) is used for characterising non linear output responses in terms of material removal rate and surface finish. Modeled results are validated with experimental values.

Surface Finishing of Micro-channels Using Low Kinetic Energy Abrasives

Abrasive jet micro-machining (AJM) is a promising technique to machine micro-features in brittle and ductile materials. However, the roughness of micro-channels machined using AJM is generally greater than that from other methods of micro-machining such as wet etching. Previous investigators have suggested that the roughness of AJM surfaces can be reduced by post-blasting with abrasive particles at a low kinetic energy. This approach was investigated by measuring the roughness reduction of a reference unmasked channel in borosilicate glass as a function of post-blasting particle size, shape, velocity, dose, and impact angle. The roughness of the reference channel decreased up to 70% of its initial value after post-blasting. It was found that post-blasting with smaller particles ultimately resulted in smoother surface, but at the penalty of requiring a relatively high particle dose, and consequently a significantly increased channel depth before reaching the steady-state roughness. Hence, finishing with small particles until reaching the steady-state is not practical when a shallow channel is desired.

Photocatalytic Decolorization of Methylene Blue in a Glass Channel Microreactor

Photocatalytic Decolorization of Methylene Blue in a Glass Channel Microreactor

Separation behavior of short single‐ and double‐stranded DNA in 1 micron and 100 nm glass channels

Micro- and nanofluidic lab-on-chip technology offers the unique capability of high-resolution separation, identification, and manipulation of biomolecules with broad applications in chemistry, biology, and medicine. In this work, we probe the effects of ionic strength on separation of ss- and dsDNA within 1 micron and 100 nm-deep glass channels. Separation behavior of DNA is influenced by a number of parameters, including ionic strength, melting temperature, strand length, strand conformation, and channel size. Specifically, we find a shift in the observed mobility of 10-bp (base pair) dsDNA for different ionic strengths due to changes in kinetic parameters, underlying the importance of these considerations when working with short DNA. For 50-base DNA, the electrophoretic mobility difference between ss- and dsDNA increases as the ionic strength increases due to changes in conformation of the ssDNA. Finally, we find that decreasing channel size decreases the absolute electrophoretic mobility of 10- and 20-bp ss- and dsDNA, due to both hydrodyamic confinement and electric double layer (EDL) interactions. We hypothesize that about 4% mobility reduction is due to hydrodynamic confinement, which is observed at all ionic strengths, and further reduction is due to EDL interactions between the DNA and the channel walls, only observed at low ionic strengths.

Thermal conductivity and electrical resistivity of bulk indium and indium embedded in 7-nm channels of porous borosilicate glass

A “porous glass + indium” nanocomposite has been prepared. The thermal conductivity κ(T) and electrical resistivity ρ(T) of the nanocomposite have been measured in the temperature range 5–300 K, and their fractions accounted for by nanoindium embedded in 7-nm channels of the porous glass have been determined. For comparison, κ and ρ of the bulk polycrystalline indium sample have been measured in the same temperature range. The electronic and phonon components of the thermal conductivity have been calculated for the nanoindium and bulk indium. It has been demonstrated that, as the result of the emergence of boundary electron and phonon scattering in the nanoindium, the electrical resistivity of this material becomes larger, and the phonon thermal conductivity, smaller than those of the bulk indium.