scholarly journals Microfluidic In-Flow Decantation Technique Using Stepped Pillar Arrays and Hydraulic Resistance Tuners

Micromachines ◽  
2019 ◽  
Vol 10 (7) ◽  
pp. 471 ◽  
Author(s):  
Gangadhar Eluru ◽  
Pavan Nagendra ◽  
Sai Siva Gorthi
Keyword(s):  
Design Theory ◽  
Free Fluid ◽  
Experimental Characterization ◽  
Flow Focusing ◽  
Liquid Component ◽  
Sample Handling ◽  
Depth Direction ◽  
Pillar Arrays ◽  
Potential Applications ◽  
Fluid Channel

Separating the particles from the liquid component of sample solutions is important for several microfluidic-based sample preparations and/or sample handling techniques, such as plasma separation from whole blood, sheath-free flow focusing, particle enrichment etc. This paper presents a microfluidic in-flow decantation technique that provides the separation of particles from particle-free fluid while in-flow. The design involves the expansion of sample fluid channel in lateral and depth directions, thereby producing a particle-free layer towards the walls of the channel, followed by gradual extraction of this particle-free fluid through a series of tiny openings located towards one-end of the depth-direction. The latter part of this design is quite crucial in the functionality of this decantation technique and is based on the principle called wee-extraction. The design, theory, and simulations were presented to explain the principle-of-operation. To demonstrate the proof-of-principle, the experimental characterization was performed on beads, platelets, and blood samples at various hematocrits (2.5%–45%). The experiments revealed clog-free separation of particle-free fluid for at least an hour of operation of the device and demonstrated purities close to 100% and yields as high as 14%. The avenues to improve the yield are discussed along with several potential applications.

scholarly journals Microencapsulation of indocyanine green for potential applications in image-guided drug delivery

Lab on a Chip ◽  
2015 ◽  
Vol 15 (3) ◽  
pp. 646-649 ◽  
Author(s):  
Zhiqiang Zhu ◽  
Ting Si ◽  
Ronald X. Xu
Keyword(s):  
Drug Delivery ◽  
Stainless Steel ◽  
Indocyanine Green ◽  
Experimental Setup ◽  
Flow Focusing ◽  
Image Guided ◽  
Potential Applications ◽  
Image Guided Drug Delivery

Schematic illustration of the LDCFF experimental setup. We used easily obtained stainless steel coaxial needles to produce ICG encapsulated liposomes by using a liquid-driven coaxial flow-focusing (LDCFF) method.

Application of Axiomatic Design Theory to a Microfluidic Device for the Production of Uniform Water-in-Oil Microspheres Adapting an Integration Method

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Ki-Young Song ◽  
Wen-Jun Zhang ◽  
Madan M. Gupta
Keyword(s):  
Aqueous Phase ◽  
Microfluidic Device ◽  
Design Theory ◽  
Low Cost ◽  
Applied Pressure ◽  
Axiomatic Design ◽  
Immiscible Fluids ◽  
Hydrodynamic Flow ◽  
Flow Focusing ◽  
Axiomatic Design Theory

This work describes a novel microfluidic method to generate uniform water-in-oil (W/O) microspheres using the phase separation technique. Axiomatic design theory (ADT) was employed for the conceptual design of microchannel systems, and ADT verified that the proposed microfluidic system is a decoupled design. The integration of hydrodynamic flow focusing method and crossflow method is realized in a microfluidic device with oil phase and aqueous phase. The immiscible fluids are fed by continuous air pressure. By the hydrodynamic flow focusing method, the width of the dispersed focused aqueous phase is controlled. The focused flow enters T-junction geometry downstream, and the crossflow interferes with the focused flow. By varying the applied pressure to the crossflow, the W/O microspheres are formed at the T-junction. Based on this approach, the size of the W/O microspheres can be successfully controlled from 16 μm to 35 μm in diameter within about 5% of variation. The present method has advantages such as good sphericity, few satellite droplets, active control of the microsphere diameter, and high throughput with the simple and low cost process. To achieve the promising results, this integrating method reveals high potential for production of polymer based microspheres.

Straightforward production of encoded microbeads by Flow Focusing: Potential applications for biomolecule detection

2006 ◽  
Vol 324 (1) ◽  
pp. 19-26 ◽  
Author(s):  
A.M. Gañán-Calvo ◽  
L. Martín-Banderas ◽  
R. González-Prieto ◽  
A. Rodríguez-Gil ◽  
T. Berdún-Álvarez ◽  
...  
Keyword(s):  
Flow Focusing ◽  
Biomolecule Detection ◽  
Potential Applications

Microfluidic Gas Purge Valves

2009 ◽  
Author(s):  
Han-Sheng Chuang ◽  
Steven T. Wereley
Keyword(s):  
Surface Tension ◽  
Surface Tension Force ◽  
Bottom Layer ◽  
Gas Permeation ◽  
Pdms Membrane ◽  
Closed State ◽  
Gas Purge ◽  
Pneumatic Valves ◽  
Potential Applications ◽  
Fluid Channel

We present two PDMS-based gas purge valves for general lab-on-a-chip applications. The valves are devised based on a three-layer configuration comprising a top layer for fluid channels, a membrane, and a bottom layer for gas channels. The pneumatic valves work as a normal gateway for fluids when the membrane is bulged down (open state) or up (closed state) by vacuum or pressure, respectively. In a closed state, the residual gas in front of a fluid can be eliminated through a small notch or a permeable PDMS membrane by simply pumping the fluid. The purge valve with a small notch, termed surface-tension enable valve (ST valve), can resist pressure under 5.5 kPa. The liquid is retained by the surface tension force resulting from the surrounding hydrophobic walls. In contrast, the purge valve with vacuum grooves above the fluid channel, termed gas-permeation enable valve (GP valve), can resist pressure higher than 5.5 kPa. Based on permeation principle, the unwanted gas can slowly escape from the fluid channel through the PDMS membrane. The unique purge valves enable users to passively align fluids at the desire locations without actively sensing or having a feedback loop. A mixing process was successfully performed with the GP valves, showing their potential applications in microfluidics.

X-Ray Analysis of Frozen Hydrated Sections:The Unconventional Approach

1982 ◽  
Vol 40 ◽  
pp. 754-757
Author(s):  
R. Beeuwkes ◽  
A. Saubermann ◽  
P. Echlin ◽  
S. Churchill
Keyword(s):  
Ratio Method ◽  
Frozen Sections ◽  
Technical Problems ◽  
Sample Handling ◽  
X Ray ◽  
Common Group ◽  
Ideal Method ◽  
Classic Paper ◽  
Physical Principles ◽  
The Ideal

Fifteen years ago, Hall described clearly the advantages of the thin section approach to biological x-ray microanalysis, and described clearly the ratio method for quantitive analysis in such preparations. In this now classic paper, he also made it clear that the ideal method of sample preparation would involve only freezing and sectioning at low temperature. Subsequently, Hall and his coworkers, as well as others, have applied themselves to the task of direct x-ray microanalysis of frozen sections. To achieve this goal, different methodological approachs have been developed as different groups sought solutions to a common group of technical problems. This report describes some of these problems and indicates the specific approaches and procedures developed by our group in order to overcome them. We acknowledge that the techniques evolved by our group are quite different from earlier approaches to cryomicrotomy and sample handling, hence the title of our paper. However, such departures from tradition have been based upon our attempt to apply basic physical principles to the processes involved. We feel we have demonstrated that such a break with tradition has valuable consequences.

Measurements in 3D images

1991 ◽  
Vol 49 ◽  
pp. 408-409
Author(s):  
John C. Russ
Keyword(s):  
Three Dimensional ◽  
Image Plane ◽  
X Rays ◽  
Traditional Use ◽  
3D Images ◽  
Confocal Scanning Laser Microscope ◽  
Hard Materials ◽  
Depth Direction ◽  
Confocal Scanning ◽  
Confocal Scanning Laser

Three-dimensional (3D) images consisting of arrays of voxels can now be routinely obtained from several different types of microscopes. These include both the transmission and emission modes of the confocal scanning laser microscope (but not its most common reflection mode), the secondary ion mass spectrometer, and computed tomography using electrons, X-rays or other signals. Compared to the traditional use of serial sectioning (which includes sequential polishing of hard materials), these newer techniques eliminate difficulties of alignment of slices, and maintain uniform resolution in the depth direction. However, the resolution in the z-direction may be different from that within each image plane, which makes the voxels non-cubic and creates some difficulties for subsequent analysis.

An in situ and ex situ TEM study of the formation of thin cobalt silicide films by molecular beam epitaxy on the silicon (100) surface

1988 ◽  
Vol 46 ◽  
pp. 884-885
Author(s):  
D. Loretto ◽  
J. M. Gibson ◽  
S. M. Yalisove ◽  
R. T. Tung
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Defect Density ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Ex Situ ◽  
Metal Base ◽  
In Situ Experiments ◽  
Potential Applications

The cobalt disilicide/silicon system has potential applications as a metal-base and as a permeable-base transistor. Although thin, low defect density, films of CoSi2 on Si(111) have been successfully grown, there are reasons to believe that Si(100)/CoSi2 may be better suited to the transmission of electrons at the silicon/silicide interface than Si(111)/CoSi2. A TEM study of the formation of CoSi2 on Si(100) is therefore being conducted. We have previously reported TEM observations on Si(111)/CoSi2 grown both in situ, in an ultra high vacuum (UHV) TEM and ex situ, in a conventional Molecular Beam Epitaxy system.The procedures used for the MBE growth have been described elsewhere. In situ experiments were performed in a JEOL 200CX electron microscope, extensively modified to give a vacuum of better than 10-9 T in the specimen region and the capacity to do in situ sample heating and deposition. Cobalt was deposited onto clean Si(100) samples by thermal evaporation from cobalt-coated Ta filaments.

Microstructure of laser-irradiated, conducting Kapton polyimide

1995 ◽  
Vol 53 ◽  
pp. 502-503
Author(s):  
D. L. Callahan ◽  
Z. Ball ◽  
H. M. Phillips ◽  
R. Sauerbrey
Keyword(s):  
Electron Microscopy ◽  
Phase Transition ◽  
Transmission Electron Microscopy ◽  
Cross Section ◽  
Film Surface ◽  
Cross Sectional ◽  
General Utility ◽  
Transmission Electron ◽  
Considerable Debate ◽  
Potential Applications

Ultraviolet laser-irradiation can be used to induce an insulator-to-conductor phase transition on the surface of Kapton polyimide. Such structures have potential applications as resistors or conductors for VLSI applications as well as general utility electrodes. Although the percolative nature of the phase transformation has been well-established, there has been little definitive work on the mechanism or extent of transformation. In particular, there has been considerable debate about whether or not the transition is primarily photothermal in nature, as we propose, or photochemical. In this study, cross-sectional optical microscopy and transmission electron microscopy are utilized to characterize the nature of microstructural changes associated with the laser-induced pyrolysis of polyimide.Laser-modified polyimide samples initially 12 μm thick were prepared in cross-section by standard ultramicrotomy. Resulting contraction in parallel to the film surface has led to distortions in apparent magnification. The scale bars shown are calibrated for the direction normal to the film surface only.

Fabrication and characterization - by High Resolution Electron Microscopy and atom probe microanalysis - of Co-based metallic multilayer films

1990 ◽  
Vol 48 (4) ◽  
pp. 772-773
Author(s):  
Amanda K. Petford-Long ◽  
A. Cerezo ◽  
M.G. Hetherington
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
High Resolution Electron Microscopy ◽  
Atom Probe ◽  
Multilayer Films ◽  
Interface Roughness ◽  
Probe Field ◽  
Resolution Electron ◽  
Potential Applications ◽  
Field Ion Microscope

The fabrication of multilayer films (MLF) with layer thicknesses down to one monolayer has led to the development of materials with unique properties not found in bulk materials. The properties of interest depend critically on the structure and composition of the films, with the interfacial regions between the layers being of particular importance. There are a number of magnetic MLF systems based on Co, several of which have potential applications as perpendicular magnetic (e.g Co/Cr) or magneto-optic (e.g. Co/Pt) recording media. Of particular concern are the effects of parameters such as crystallographic texture and interface roughness, which are determined by the fabrication conditions, on magnetic properties and structure.In this study we have fabricated Co-based MLF by UHV thermal evaporation in the prechamber of an atom probe field-ion microscope (AP). The multilayers were deposited simultaneously onto cobalt field-ion specimens (for AP and position-sensitive atom probe (POSAP) microanalysis without exposure to atmosphere) and onto the flat (001) surface of oxidised silicon wafers (for subsequent study in cross-section using high-resolution electron microscopy (HREM) in a JEOL 4000EX. Deposi-tion was from W filaments loaded with material in the form of wire (Co, Fe, Ni, Pt and Au) or flakes (Cr). The base pressure in the chamber was around 8×10−8 torr during deposition with a typical deposition rate of 0.05 - 0.2nm/s.

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