Generation of Uniform Liquid Droplets in a Microfluidic Chip Using a High-Speed Gaseous Microflow

2016 ◽  
Author(s):  
Pooyan Tirandazi ◽  
Carlos H. Hidrovo
Keyword(s):  
Microfluidic Chip ◽  
High Speed ◽  
Gas Flow ◽  
Gaseous Medium ◽  
High Surface ◽  
Liquid Droplets ◽  
Microfluidic Systems ◽  
Alternative Scheme ◽  
Micro Particles ◽  
Wide Range

Miniaturized laboratory-on-a-chip systems have been extensively developed over the past decade as promising tools for a wide range of applications, specifically in chemical synthesis and biomedical diagnostics. Droplet-based microfluidic systems have become ubiquitous in such applications by providing essential tools to perform rapid as well as high throughput measurements on small volumes of fluids. Thus far, the majority of the research endeavors have been focused on liquid-liquid systems for generating microscale drops (typically water in oil). Droplets generated in liquid-liquid microfluidic systems tend to be very uniform in size, and due to high surface area to volume ratio of micro-droplets, heat and mass transfer occurs at higher rates as compared to continuous-flow microfluidics. Generation of droplets in a gaseous medium, on the other hand, have been widely used in applications that involve open environment liquid spraying, such as ink-jet printers. However, usually in such applications there is no control over either the size or frequency of the generated droplets, and as a result droplets formed in these systems are widely distributed in size. Here we demonstrate an alternative scheme for controlled generation of liquid droplets in a microfluidic chip using a high speed gas stream. We have incorporated the inertial effect of a high-speed gaseous medium with the flow-focusing geometry, fabricated in a PDMS chip, in order to generate droplets with controlled size. Flow regimes involved in this scheme may be divided in three main regions i.e. co-flow, jetting, and dripping among which only dripping regime is capable of producing distinct aqueous droplets in the channel. It should be noted that poor surface conditions and high gas flow rates may result in generation of satellite droplets together with the main droplet in the dripping region, which substantially affects the monodispersity of the droplets. The generated drops were collected thereafter and it is shown that monodisperse droplets with known size ranging from 50 μm to 100 μm in diameter can be achieved within the dripping flow regime. We believe this method offers beneficial opportunities for the next generation of Lab-on-a-chip devices in which the introduction of a gaseous medium is required, namely oxidation, detection of airborne particles, and formation of micro-particles and micro-gels. Furthermore, the high speed droplets generated in this method represent the basis for a new approach based on droplet pair collisions for fast efficient micromixing which provides a significant development in modern LOC and mTAS devices.

CFD SIMULATION AND CHARACTERIZATION OF A DEVICE FOR POWDERED PHARMACEUTICALS AND BIOLOGICALS DELIVERY

2006 ◽  
Vol 06 (03) ◽  
pp. 285-297
Author(s):  
FANG LIU ◽  
WEI HE ◽  
CHUNLI CAO ◽  
YI LIU
Keyword(s):  
High Speed ◽  
Cfd Simulation ◽  
Biological Effects ◽  
Particle Interaction ◽  
Mean Velocity ◽  
Micro Particles ◽  
Venturi Effect ◽  
Underlying Principle ◽  
Wide Range

Advances in molecular biology have produced a wide range of protein and peptide-based drugs. Equally, it is required to explore various technologies and capabilities to deliver those drugs. A unique medical device, the hand-held biolistics, is developed for powdered pharmaceuticals/biologicals transdermal delivery. The underlying principle is to accelerate micro-particles by means of a high-speed helium gas to an appropriate momentum to penetrate the outer layer of the skin to elicit desirable pharmaceutical/biological effects. The novelty of this hand-held biolistics is using the venturi effect to entrain micron-sized protein and peptide drugs into an established quasi-steady transonic jet flow and accelerate them toward the target. In this paper, computational fluid dynamics is utilized to characterize prototype biolistic system. The key features of gas dynamics and gas–particle interaction are presented. The overall capability of the biolistic delivery system is discussed and demonstrated. The statistical analyses show that the particles have achieved a mean velocity of 628 m/s as representatives of extracellular vaccine delivery applications.

The Microchannel of Microfluidic Chip Fabrication by Micro-Powder Blasting

2009 ◽  
Vol 76-78 ◽  
pp. 367-372
Author(s):  
Chiung Fang Huang ◽  
Yung Kang Shen ◽  
Yi Lin ◽  
Chi Wei Wu
Keyword(s):  
Microfluidic Chip ◽  
High Speed ◽  
Gas Flow ◽  
Erosion Resistance ◽  
Processing Parameters ◽  
Powder Size ◽  
Dimethyl Siloxane ◽  
Powder Blasting ◽  
Processing Procedure ◽  
Chip Fabrication

The process of micro-powder blasting is the high speed gas flow which mixed the micro-particle and gas to impact the brittle substrate by the specialized nozzle. This paper combined various diameters Al2O3 eroding particle with a novel masking technique to fabricate the pattern channels in soda glass with a width to 2000 μm and depth down to 1631 μm. The masking technology for fabricating microchannel is consisted by the combination of two polymers: 1) the elastic and thermal-curable poly-(dimethyl siloxane) (PDMS) for its erosion resistance and 2) the brittle epoxy resin SU-8 for its photosensitivity. This paper discusses the processing procedure by the different processing parameters (micro-powder impact pressure, the distance between nozzle and substrate, micro-powder size, and micro-powder impact time) to find the optimal process. The results show that the micro-powder size is the most important factor for the depth of microchannel of microfluidic chip. The surface roughness of microchannel of microfluidic chip is nearly 5-6μm.

An Ultra-High-Throughput Flow-Focusing Microfluidic Device for Creation of Liquid Droplets in Air

2017 ◽  
Author(s):  
Pooyan Tirandazi ◽  
Gabriel Tomic ◽  
Carlos H. Hidrovo
Keyword(s):  
High Throughput ◽  
High Throughput Screening ◽  
High Speed ◽  
Large Scale ◽  
3D Structure ◽  
Scale Production ◽  
Liquid Droplets ◽  
Flow Focusing ◽  
Microfluidic Systems ◽  
Uniform Array

In this paper a new microfluidic technique is proposed for ultra-high-throughput generation of micron-sized water droplets using a high-speed air. We use a 3D flow-focusing microchannel fabricated in PDMS by multilayer lithography process. The interaction of liquid and gas created three main flow conditions which are: Flooded, Dripping, and Jetting. We characterize the Jetting regime where a capillary jet surrounded by the air breaks up into uniform array of droplets. Frequency of generation and droplet size are reported for the jetting regime under different liquid and gas flows. It was possible to obtain 25μm diameter droplets and much higher frequencies (f≈120 kHz) compared to the state-of-the-art microfluidic systems. We believe the advantages of this platform enables many novel applications such as high-throughput screening of airborne targets and large-scale production of oil-free particles. The 3D structure of this device also eliminates the limitation of the conventional droplet-based microfluidic systems, namely clogging issues due to particle aggregation.

The Effects of Wetting and Surface Roughness on Liquid Metal Droplet Bouncing

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Wen-Kai Hsiao ◽  
Jung-Hoon Chun ◽  
Nannaji Saka
Keyword(s):  
Surface Roughness ◽  
High Speed ◽  
Image Data ◽  
Metal Droplet ◽  
Target Surface ◽  
Spray Forming ◽  
Liquid Droplets ◽  
Conservation Of Energy ◽  
Wetting Properties ◽  
Wide Range

In droplet-based manufacturing processes, such as dropwise rapid prototyping, solder bumping, and spray forming, the quality of the deposit is adversely affected by bouncing of liquid droplets off the target surfaces. This study investigates the effects of wetting and surface roughness on the bouncing phenomenon. An analytical model, based on the conservation of energy during deposition, was developed to correlate wetting and surface roughness to a dimensionless droplet bouncing potential. In addition, experiments were conducted to image the deposition behavior of Sn-37 wt % Pb solder droplets, averaging 280 μm in diameter, on prepared substrates with a wide range of wetting properties and roughness levels. The high-speed image data correlate well with the model prediction that droplets are likely to bounce as a target surface becomes less wetting or is roughened.

Modeling and Experimental Investigation of Bubble Formation in Shear-Thinning Liquids

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Mohamad Taghi Esfidani ◽  
Mohammad Reza Oshaghi ◽  
Hossein Afshin ◽  
Bahar Firoozabadi
Keyword(s):  
Power Law ◽  
High Speed ◽  
Gas Flow ◽  
Bubble Formation ◽  
Experimental Studies ◽  
Methyl Cellulose ◽  
Operating Conditions ◽  
Wide Range ◽  
Bubble Sizes ◽  
Newtonian Liquids

This investigation presents both theoretical and experimental studies on the size of a growing bubble in power-law non-Newtonian liquids. At first, some previous works on the prediction of bubble size in Newtonian liquids have been extended by considering the balance of forces acting on the bubble at the moment of separation. Predicted bubble sizes were validated against the experimental results for a wide range of operating conditions, including different gas flow rates and needle diameters as well as a wide range of physical properties of the Newtonian liquids. Furthermore, in order to determine the size of the bubbles formed in power-law non-Newtonian liquids with a similar analysis, the effective shear rate of bubble growth was calculated in which the rheological properties of fluid were taken into account and subsequently the viscosity of the fluid was modified. Theoretically obtained bubble sizes for non-Newtonian liquids are in a good agreement with our experimental high-speed video observations of three carboxyl methyl cellulose (CMC) solutions.

A Phenomenological Model for Combustion and Emissions in Small Bore, High Speed, Direct Injection Diesel Engines

2005 ◽  
Author(s):  
N. A. Henein ◽  
I. P. Singh ◽  
L. Zhong ◽  
Y. Poonawala ◽  
J. Singh ◽  
...  
Keyword(s):  
Diesel Engine ◽  
Diesel Engines ◽  
Phenomenological Model ◽  
High Speed ◽  
Gas Flow ◽  
Fuel Injection ◽  
Direct Injection ◽  
Injection System ◽  
Injection Process ◽  
Wide Range

This paper introduces a phenomenological model for the fuel distribution, combustion, and emissions formation in the small bore, high speed direct injection diesel engine. A differentiation is made between the conditions in large bore and small bore diesel engines, particularly regarding the fuel impingement on the walls and the swirl and squish gas flow components. The model considers the fuel injected prior to the development of the flame, fuel injected in the flame, fuel deposited on the walls and the last part of the fuel delivered at the end of the injection process. The model is based on experimental results obtained in a single-cylinder, 4-valve, direct-injection, four-stroke-cycle, water-cooled, diesel engine equipped with a common rail fuel injection system. The engine is supercharged with heated shop air, and the exhaust back pressure is adjusted to simulate actual turbo-charged diesel engine conditions. The experiments covered a wide range of injection pressures, EGR rates, injection timings and swirl ratios. Correlations and 2-D maps are developed to show the effect of combinations of the above parameters on engine out emissions. Emphasis is made on the nitric oxide and soot measured in Bosch Smoke Units (BSU).

Microfabrication research at the National Submicron Facility

1983 ◽  
Vol 41 ◽  
pp. 86-89
Author(s):  
E.D. Wolf
Keyword(s):  
Integrated Circuits ◽  
Particle Physics ◽  
High Speed ◽  
New Technology ◽  
High Energy ◽  
High Energy Particle ◽  
New Science ◽  
Wide Range ◽  
Intermediate Domain ◽  
Circuit Function

Most microelectronics devices and circuits operate faster, consume less power, execute more functions and cost less per circuit function when the feature-sizes internal to the devices and circuits are made smaller. This is part of the stimulus for the Very High-Speed Integrated Circuits (VHSIC) program. There is also a need for smaller, more sensitive sensors in a wide range of disciplines that includes electrochemistry, neurophysiology and ultra-high pressure solid state research. There is often fundamental new science (and sometimes new technology) to be revealed (and used) when a basic parameter such as size is extended to new dimensions, as is evident at the two extremes of smallness and largeness, high energy particle physics and cosmology, respectively. However, there is also a very important intermediate domain of size that spans from the diameter of a small cluster of atoms up to near one micrometer which may also have just as profound effects on society as “big” physics.

scholarly journals Atmospheric Pressure Plasma Deposition of TiO2: A Review

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 2931
Author(s):  
Soumya Banerjee ◽  
Ek Adhikari ◽  
Pitambar Sapkota ◽  
Amal Sebastian ◽  
Sylwia Ptasinska
Keyword(s):  
Atmospheric Pressure ◽  
Gas Flow ◽  
Plasma Deposition ◽  
Atmospheric Pressure Plasma ◽  
Cost Savings ◽  
Historical Background ◽  
Pressure Plasma ◽  
Wide Range ◽  
The Status ◽  
Deposition Techniques

Atmospheric pressure plasma (APP) deposition techniques are useful today because of their simplicity and their time and cost savings, particularly for growth of oxide films. Among the oxide materials, titanium dioxide (TiO2) has a wide range of applications in electronics, solar cells, and photocatalysis, which has made it an extremely popular research topic for decades. Here, we provide an overview of non-thermal APP deposition techniques for TiO2 thin film, some historical background, and some very recent findings and developments. First, we define non-thermal plasma, and then we describe the advantages of APP deposition. In addition, we explain the importance of TiO2 and then describe briefly the three deposition techniques used to date. We also compare the structural, electronic, and optical properties of TiO2 films deposited by different APP methods. Lastly, we examine the status of current research related to the effects of such deposition parameters as plasma power, feed gas, bias voltage, gas flow rate, and substrate temperature on the deposition rate, crystal phase, and other film properties. The examples given cover the most common APP deposition techniques for TiO2 growth to understand their advantages for specific applications. In addition, we discuss the important challenges that APP deposition is facing in this rapidly growing field.

Assessment of Commercial Off-the-Shelf Tissue Adhesives for Sealing Military-Relevant Corneal Perforation Injuries

2021 ◽  
Author(s):  
Eric J Snider ◽  
Lauren E Cornell ◽  
Brandon M Gross ◽  
David O Zamora ◽  
Emily N Boice
Keyword(s):  
Intraocular Pressure ◽  
High Speed ◽  
Anterior Segment ◽  
Ocular Tissue ◽  
Corneal Tissue ◽  
Corneal Perforation ◽  
Tissue Adhesives ◽  
Open Globe ◽  
Wide Range ◽  
Commercial Off The Shelf

ABSTRACT Introduction Open-globe ocular injuries have increased in frequency in recent combat operations due to increased use of explosive weaponry. Unfortunately, open-globe injuries have one of the worst visual outcomes for the injured warfighter, often resulting in permanent loss of vision. To improve visual recovery, injuries need to be stabilized quickly following trauma, in order to restore intraocular pressure and create a watertight seal. Here, we assess four off-the-shelf (OTS), commercially available tissue adhesives for their ability to seal military-relevant corneal perforation injuries (CPIs). Materials and Methods Adhesives were assessed using an anterior segment inflation platform and a previously developed high-speed benchtop corneal puncture model, to create injuries in porcine eyes. After injury, adhesives were applied and injury stabilization was assessed by measuring outflow rate, ocular compliance, and burst pressure, followed by histological analysis. Results Tegaderm dressings and Dermabond skin adhesive most successfully sealed injuries in preliminary testing. Across a range of injury sizes and shapes, Tegaderm performed well in smaller injury sizes, less than 2 mm in diameter, but inadequately sealed large or complex injuries. Dermabond created a watertight seal capable of maintaining ocular tissue at physiological intraocular pressure for almost all injury shapes and sizes. However, application of the adhesive was inconsistent. Histologically, after removal of the Dermabond skin adhesive, the corneal epithelium was removed and oftentimes the epithelium surface penetrated into the wound and was adhered to inner stromal tissue. Conclusions Dermabond can stabilize a wide range of CPIs; however, application is variable, which may adversely impact the corneal tissue. Without addressing these limitations, no OTS adhesive tested herein can be directly translated to CPIs. This highlights the need for development of a biomaterial product to stabilize these injuries without causing ocular damage upon removal, thus improving the poor vision prognosis for the injured warfighter.

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