Applied Air Pressure Research Articles

Formation of Microdroplets in Liquids Utilizing Active Pneumatic Choppers on a Microfluidic Chip

Monodispersed emulsions are of great significance for a variety of applications. The current study reports a new microfluidic system capable of formation of microdroplets in liquids for emulsification applications. This new emulsion chip can precisely generate uniform droplets using a novel combination of hydrodynamic-focusing and liquid-chopping techniques. Experimental data show that microdroplets with diameters ranging from 6 to 100 mum with a variation less than 3% can be precisely generated. The size of the droplets is tunable using three approaches including adjusting the relative sheath/sample flow velocity ratios, the applied air pressure and the applied chopping frequency. Moreover, focusing and chopping of multiple flows has been demonstrated to increase the emulsion process throughput

Performance evaluation of a dental handpiece in simulation of clinical finishing using a novel 2DOF in vitro apparatus

This paper reports on the performance evaluation of a dental handpiece in simulation of clinical finishing using a novel two-degrees-of-freedom (2DOF) in vitro apparatus. The instrumented apparatus consisted of a two-dimensional computer-controlled coordinate worktable carrying a dental handpiece, a piezoelectric force dynamometer, and a high-speed data acquisition and signal conditioning system for simulating the clinical operations and monitoring the dental finishing processes. The performance of the dental handpiece was experimentally evaluated with respect to rotational speed, torque, and specific finishing energy under the applied clinical finishing conditions. The results show that the rotational speeds of the dental handpiece decreased by increasing either the depth of cut or the feed rate at a constant clinically applied air pressure and water flowrate. They also decreased when increasing both the tangential and normal finishing forces. The specific finishing energy decreased with an increase in either depth of cut or feed rate, while the finishing torque increased as either the depth of cut or the feed rate was increased. Implications of these results were to provide guidance for proper applications of dental handpieces in clinical practice.

Fabrication, experiment of a microactuator using magnetic fluid for micropump application

This paper presents the characteristics of the first microactuator using magnetic fluid (MF). MF actuators with flat and corrugated diaphragms are fabricated by the micromachining technique and their deflections are measured. The MF actuator consists of an inductor, a fluid chamber filled with magnetic fluid, and a parylene diaphragm. In the presence of the magnetic field, magnetic fluid easily deforms its shape and generates some pressure. The relation between the MF pressure and magnetic flux density is obtained by the comparison of the deflection for the applied air pressure with that for the MF pressure. At 110 Gauss, the deflection of MF actuator with corrugated parylene diaphragm is more than 200 μm and the generated MF pressure is 2.8 kPa. The successful operation of the first MF actuator shows the high potential for the application to the micromachined devices.

A Hydrogel-Based Implantable Micromachined Transponder for Wireless Glucose Measurement

In this paper, we report on the design and characterization of a new hydrogel-based implantable wireless glucose sensor. The basic device structure is a passive [inductor/capacitor (LC)] micromachined resonator coupled to a stimuli-sensitive hydrogel, which is confined between a stiff nanoporous membrane and a thin glass diaphragm. As glucose molecules pass through the nanoporous membrane, the hydrogel swells and deflects the flexible glass diaphragm, which is the movable plate of the variable capacitor in the totally integrated passive LC resonator. The corresponding change in resonant frequency can be remotely detected. A glucose- sensitive phenylboronic acid-based hydrogel was loaded into the microtransponder, and its sensitivity and time response were measured. Prior to hydrogel loading, the sensitivity of the pressure sensor to applied air pressure was measured to be -222 kHz/kPa over the frequency range 51-->42 MHz. The sensor showed a sensitivity of -34.3 kHz/mM over the glucose concentration range 0-20 mM (at pH 7.4), and a response time of 90 min. The dynamic response, although unacceptable at such values, can be easily improved by decreasing the hydrogel thickness and reducing the sensor and porous membrane thicknesses. The transponder's overall dimensions were 5x5x0.8 mm3, small enough for subcutaneous implantation.

Development of a tapping device: a new needle insertion method for prostate brachytherapy

The purpose of this study is to develop and test a tapping device for needle insertion for prostate brachytherapy. This device will tap the needle into the prostate with a certain, well-defined, amount of momentum, instead of the currently used method of pushing the needle. Because of the high needle insertion velocity, we expect prostate motion and deformation to be less compared to current methods. We measured the momentum that is applied when manually tapping the needle into the prostate and found a mean momentum of 0.50 ± 0.07 N s. The tapping device is pneumatically driven and we found that the delivered momentum increased linearly with the applied air pressure. The efficacy of the tapping device was tested on a piece of beef, placed on a freely moving and rotating platform. A significant correlation was found between the applied pressure and the rotation and displacement of the beef. Displacements and rotations were minimal for the highest pressure (4 bar) and amounted to only 2 mm and 6°, respectively. Higher air pressures will further reduce displacements and rotations.

A Multi-Step Linear Approximation Method for Nonlinear Analysis of Stress and Deformation of Coated Plain-Weave Fabric

The elastic constants are approximately determined using a multi-step linear approximation method for more accurate material nonlinear analysis of coated fabric membrane structures. The approximate determination is performed within each quadrilateral or triangular surface defined on the surfaces of the biaxial elongation property formed with the data of stress-strain curves measured by biaxial extension testings. Two types of 40 × 40 cm square flat membrane model of a PTFE coated plain-weave glass fiber fabric are analyzed applying finite element method adapting a 20-steps linear approximation method. One of the models is an inplane deformation model subjected to biaxial extension under the condition of stress ratio of 1:1. The stress-strain response in the central region of the membrane is analyzed. And the other model is a membrane deformed by the application of air pressure. The relation between the central deflection and the pressure is analyzed. The results of analysis showed excellent coincidences with experimental results.

1P1-C01 円筒型弾性薄膜を用いた空圧式マイクロポンプの提案・開発

Pneumatically-driven micropump for micro chemical devices were proposed and developed. As a fluidic transport element, we contrived a new pump element that has a cylindrical elastic membrane inside a micro chamber. The flexible membrane was deformed by applying air pressure through a channel for working fluid. The pump elements are fabricated by microstereolithography with an elastic photopolymer. By using the three pump elements, a peristalic micropump was developed. The micropump could transport both water and air with sufficient flow rate for micro chemical devices. Since the pneumatically-driven micropump is simple and low cost, they will be widely used in disposable biochips for medical diagnostics.

Automated MEMS-based Drosophila embryo injection system for high-throughput RNAi screens

We have developed an automated system based on microelectromechanical systems (MEMS) injectors for reliable mass-injection of Drosophila embryos. Targeted applications are high-throughput RNA interference (RNAi) screens. Our injection needles are made of silicon nitride. The liquid to be injected is stored in an integrated 500 nl reservoir, and an externally applied air pressure pulse precisely controls the injected volume. A steady-state water flow rate per applied pressure of 1.2 nl s(-1) bar(-1) was measured for a needle with channel width, height and length of 6.1 microm, 2.3 microm and 350 microm, respectively. A typical volume of 60 pl per embryo can be reliably and rapidly delivered within tens of milliseconds. Theoretical predictions of flow rates match measured values within +/-10%. Embryos are attached to a glass slide surface and covered with oil. Packages with the injector chip and the embryo slide are mounted on motorized xyz-stages. Two cameras allow the user to quickly align the needle tip to alignment marks on the glass slide. Our system then automatically screens the glass slide for embryos and reliably detects and injects more than 98% of all embryos. Survival rates after deionized (DI) water injection of 80% and higher were achieved. A first RNAi experiment was successfully performed with double-stranded RNA (dsRNA) corresponding to the segment polarity gene armadillo at a concentration of 0.01 microM. Almost 80% of the injected embryos expressed an expected strong loss-of-function phenotype. Our system can replace current manual injection technologies and will support systematic identification of Drosophila gene functions.

MAGMAsoft를 이용한 자동차 변속기용 Gear Housing의 다이캐스팅 주조공정 설계

In the die casting process, the flow of liquid metal has significant influence on the quality of casting products and die life. For the optimal process design of gear housing of automobile transmission, various analyses were performed in this study by using computer simulation code, MAGMAsoft. The simulation has been focused on the molten metal behaviors during the mold filling and solidification stages for the sound casting products. Also internal defects were predicted by application of air pressure and feeding criteria.

Brachio-ankle pulse wave velocity and cardio-ankle vascular index (CAVI)

In order to diagnose arteriosclerosis in any part of the body, pulse wave velocity (PWV) measurement is a useful approach. However, it is considered that the technique of PWV measurement should be simplified. A new method for measuring PWV has therefore been proposed in Japan. The PWV of the brachial artery (ba) and the ankle was measured by applying air pressure with the aid of a volume plethysmograph. Comparisons between the baPWV measurement method and the conventional method are currently being performed. Since satisfactory results have been obtained to date, baPWV has gained popularity throughout Japan. Since this method measures PWV in the arm and foot, it may be said that aortic PWV is not reflected though a large amount of past PWV measurements. BaPWV is influenced by blood pressure. With the baPWV technique, blood pressure compensation is not carried out. Furthermore, the pulse pressure is measured by air pressure; therefore any stimulus that exerts pressure on an artery may influence these results. Due to these reasons, a cardio-ankle vascular index (CAVI) has been proposed in which the pressure wave form indicating the closing of the aortic valve appears in the form of an arterial pressure wave after a fixed delay time. This delay is the time difference between the actual closing of the aortic valve and the measuring point. Prior to the introduction of baPWV, PWV was measured in the carotid artery and foot. As in traditional PWV, baPWV uses the delay time, but between the brachial artery and the ankle artery. However, the carotid artery differs from the brachial artery, and the measured value differs depending on whether the arteriosclerosis is present in the carotid artery or the brachial artery. CAVI is calculated from the ECG, PCG, brachial artery waveform and ankle artery waveform using a special algorithm. This new method represents a breakthrough in the diagnosis of atherosclerosis.

Numerical simulation of compressed air tunnel advance

Compressed air in shallow tunnelling is used to counteract the tendency of water to flow into the opened space. The method of compressed air has gained new importance recently, because in urban areas it does not influence the surrounding groundwater. Another advantage is that the transportation of existing contaminants into the direction of the tunnel can be prevented. One major disadvantage is that the excavation work takes place under severe conditions with respect to the health of the tunnellers. The amount of air flow varies depending on the soil conditions, the geometry of the tunnel and the applied air pressure. Air flow takes place both through the unsupported tunnel face and shrinkage cracks of the shotcrete lining. The required air pressure must be controlled and adjusted if necessary continuously. During tunnelling, advance air flows into the surrounding soil. The primary fully saturated soil becomes partially saturated. This has large influence on the amount of air flowing not only through the tunnel face but also through cracks in the shotcrete lining. While the amount of air flow through the tunnel face is relatively constant, the amount of air flow through the shrinkage cracks increases with the length of the excavated tunnel section and becomes the governing factor. A large-scale laboratory test to simulate the air flow through the shotcrete lining and the soil was conducted. Different parameters have been varied. These parameters were: (1) the amount of air pressure; (2) the width of the cracks in the lining; (3) the thickness of the lining and (4) the soil type. Subsequently a numerical model was developed that allows the simulation of the flow behaviour in the laboratory test and further extended to simulations of compressed air tunnel advance. TOUGH2 was chosen to perform the numerical analyses. To compute the air flow through the tunnel face and the shotcrete lining a three-dimensional model was developed including the progress in tunnel advance. To model the tunnel advance elements were sequentially removed in the tunnel face area. The model considered the relative permeability saturation dependency of a soil. In the present contribution two models with varying tunnel advance rates were compared. The reduction of the total amount of air flow due to an increased tunnel advance rate was demonstrated. The model with a tunnel advance rate of v = 1 m/d demands about 80% more air per hour than a model with an advance rate of v = 3 m/d. (A). "Reprinted with permission from Elsevier". For the covering abstract see ITRD E124500.

Static and dynamic removal rates of a new hydrodynamic polishing tool.

A new tool for hydrodynamic radial polishing, HyDra, allows for the local polishing of optical surfaces with a controllable wear rate. The results of the removal rate for different polisher types and sizes, applied air pressures for slurry expulsion, and tool height with respect to the working surface, are reported. We present a numerical analysis of the volumetric removal rate for the dynamic experiments as well as a comparison with a similar technique.

Use of applied air pressure to improve the baking properties of whey protein isolates in angel food cakes

Whey protein isolate (WPI) possesses limited application in angel food cake baking compared to liquid egg white (LEW). This study was conducted to determine whether applying air pressure in the oven during baking would improve the baking properties of WPI in angel food cakes. A special oven was designed for baking at oven air pressures up to 1.5 bar. Control angel food cakes were formulated with LEW (100/0) as its protein source and WPI-containing cakes were formulated with a mixture of 75 mL/100 mL LEW and 25 mL/100 mL WPI solution (75/25) or a mixture of 50 mL/100 mL LEW and 50 mL/100 mL WPI solution (50/50). Cakes were baked at atmospheric air pressure (AP) and at constant applied air pressure (CAP) or variable applied air pressure vs. baking time (VAP) to prevent overexpansion and collapse of WPI-containing cake batter. Cakes 75/25 and 50/50 baked at VAP exhibited improved physical, textural and sensory properties compared to those baked at AP or CAP conditions. Cakes 75/25 baked at VAP compared well with control angel food cakes baked at AP. Although 50/50 cakes baked at VAP were improved slightly over those baked at AP, none of them exhibited satisfactory properties. Therefore, additional research is needed to optimize baking conditions for cakes formulated with less than 75 mL/100 mL LEW.

Pressure-assisted capillary electrophoresis electrospray ionization mass spectrometry for analysis of multivalent anions.

We describe a method, based on pressure-assisted capillary electrophoresis coupled to electrospray ionization mass spectrometry (PACE/ESI-MS), that allows the simultaneous and quantitative analysis of multivalent anions, such as citrate isomers, nucleotides, nicotinamide-adenine dinucleotides, and flavin adenine dinucleotide, and coenzyme A (CoA) compounds. Key to the analysis was using a noncharged polymer, poly(dimethylsiloxane), coated to the inner surface of the capillary to prevent anionic species from adsorbing onto the capillary wall. It was also necessary to drive a constant liquid flow toward the MS by applying air pressure to the inlet capillary during electrophoresis to maintain a conductive liquid junction between the capillary and the electrospray needle. Although theoretical plates were inferior to those obtained by CE/ESI-MS using a cationic polymer-coated capillary, the PACE/ESI-MS method improved reproducibility and sensitivity of these anions. Eighteen anions were separated by PACE and selectively detected by a quadrupole mass spectrometer with a sheath-flow electrospray ionization interface. The relative standard deviations (n = 6) of the method were better than 0.6% for migration times and between 1.4% and 6.2% for peak areas. The detection limits for these species were between 0.4 and 3.7 micromol/L with pressure injection of 50 mbar for 30 s (30 nL), that is, mass detection limits calculated in the range from 12 to 110 fmol at a signal-to-noise ratio of 3. The utility of the method was demonstrated by analysis of citrate isomers, nucleotides, dinucleotides, and CoA compounds extracted from Bacillus subtilis cells.

Hydrogel-Actuated Capacitive Transducer for Wireless Biosensors

This article introduces a new type of transducer that combines capacitive pressure sensing techniques with biosensitive hydrogels, using an adaptable MEMS fabrication platform. Hydrogel swelling in response to analyte concentration exerts contact pressure on a deformable conducting diaphragm, producing a capacitance change. Initial results are reported for testing device feasibility. Uncrosslinked PHEMA hydrogel was tested for swelling pressure in response to calcium nitrate tetrahydrate. Diaphragm deflection due to applied air pressure was measured on NiTi-based diaphragms and compared with hydrogel-actuated deflections of the same diaphragms to determine the pressure generating characteristics of the hydrogel. The PHEMA sample exhibited greatest sensitivity in the concentration range 0–0.5 M, generating an average of 110 mN/M/μl. The device was incorporated into a passive LC resonant circuit. Resonance frequency was measured as a function of applied air pressure, in the range of pressures generated by hydrogel swelling. Resonance frequency shifted from 66 MHz to 33 MHz over the pressure range 0–32 kPa, corresponding to an estimated average sensitivity of 66 Hz per μmol of calcium nitrate tetrahydrate over the range 0–0.5 M.

Analysis of Particle Velocity and Temperature Distribution of Struck Surface in Fine Particle Peening.

This study examines numerical analysis of particle velocity and temperature distribution of struck material surface in fine particle peening. When the particle is accelerated using a direct-pressure type, the velocity of a 50 μm particle, just before striking the metal surface, was calculated to be 222 m/s. In applying air pressure, the acceleration of fine particles show significant increase compared to larger sizes. Moreover, the experimental values agree well with the calculated ones. On the other hand, the temperature distributions show the maximum surface temperature to be 1500 K and cools instantly.

POSTDIE EXTRUSION OF PLASTIC PIPE

In continuous plastic pipe extrusion, melt emerges from an annular die and is then freely drawn down into a sizing sleeve. Here, we investigate this extensional flow with and without internally applied air pressure. For the case without internal air pressure, an analytic solution is derived. For the case with internal air pressure, a numerical solution is presented, where differential equations for the melt cone shape are derived from a force balance. Design curves are then constructed from the solutions to these models. These curves are helpful in predicting pipe-extrusion operating conditions for the postdie region.

True Thermal Conductivity Determination of Moist Porous Food Materials at Elevated Temperatures

ABSTRACTThermal conductivity (k) of bread samples, moisture content 5% to 44%, (w/w, wet basis) and porosity 0.18 to 0.90, was measured in a sealed stainless steel vessel using the probe method from 25 to 85°C. Significant differences were observed in measured thermal conductivity before and after air pressure was applied to the sample indicating the influence of vapor phase moisture migration on thermal conductivity. The difference increased as temperature and moisture content were increased. True thermal conductivity of bread was found to agree with predictions using a volume fraction model when moisture migration was completely suppressed at an applied air pressure of 18 atm.

Interpretation of Prematurely Terminated Air‐Pressurized Slug Tests

AbstractAir‐pressurized slug tests offer a means of estimating formation transmissivity and storativity without extensive downhole equipment and in situations where contact with formation fluids may pose a health concern. An air‐pressurized slug test, as discussed in this paper, consists of applying a constant pressure to the column of air in a well, monitoring the declining water level, and then releasing the air pressure and monitoring the recovering water level. If the maximum declining (or new equilibrium) water level is achieved for a constant applied air pressure, the slug‐test solution of Cooper et al. (1967) can be used to interpret the water‐level recovery data and estimate the formation properties. In low‐permeability terranes, the time required to achieve the equilibrium water level during the pressurized part of the test may be too long for practical purposes, and it may be necessary to terminate the applied air pressure prior to establishing a new equilibrium. To analyze data from such tests, a solution to the boundary‐value problem for the declining and recovering water level during an air‐pressurized slug test is developed for an arbitrary time‐dependent air pressure applied to the well. For the special case of applying a constant air pressure and then reducing it instantaneously to atmospheric pressure at a prescribed time, the general solution reduces to the superposition of the solution of Cooper et al. (1967) at two displaced times. Type curves are generated to estimate formation transmissivity and storativity from the recovering water level associated with prematurely terminated air‐pressurized slug tests. The application of the type curves is illustrated in tests conducted in wells completed in the Minnelusa and Madison aquifers near Rapid City and Spearfish, South Dakota.

Protein nebulization: I. Stability of lactate dehydrogenase and recombinant granulocyte-colony stimulating factor to air-jet nebulization

The effect of air-jet nebulization on the stability of two proteins was examined. Lactate dehydrogenase (LDH) and recombinant human granulocyte colony stimulating factor (rhG-CSF) were chosen as the test proteins. The enzymatic activity of LDH can be readily monitored using a colorimetric assay. rhG-CSF was also studied as it has potential to be delivered to the systemic circulation via the lung. Aerosolization of LDH using a three-jet Collison nebulizer resulted in a time-dependent loss of enzymatic activity. The extent of inactivation was dependent upon the applied air pressure and the volume of fluid in the nebulizer reservoir. Inactivation at 10 and 40 psig was 12 ± 5( n = 6) and 18 ± 10% ( n = 6), respectively, after a period of 10 min nebulization using a 40 ml starting volume, whereas an initial volume of 10 ml resulted in 57 ± 14% loss of activity after 10 min at 40 psig. rhG-CSF was affected in two ways by aerosolization. First, non-covalent aggregates were formed with time as observed by size exclusion chromatography. Second, a chemical change was induced and this was reflected in the formation of a higher mobility band on native gel electrophoresis. The change in mobility was thought to be due to an altered charge state of the protein, possibly through deamidation. Both the aggregated and degraded forms accounted for approx. 40% of the protein after 10 min. Polyethylene glycol (PEG) 1000 markedly reduced the deleterious effects of nebulization on the proteins. A 10 ml solution of protein containing 1% w/v PEG 1000 retained ≈ 100% of the original activity of LDH after 10 min nebulization at 40 psig while both forms of rhG-CSF degradation were held to less than 10% for the same set of operating conditions.