scholarly journals Experimental Analysis of Laser Micromachining of Microchannels in Common Microfluidic Substrates

Micromachines ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 138
Author(s):  
Prashanth Reddy Konari ◽  
Yung-Dai Clayton ◽  
Melville B. Vaughan ◽  
Morshed Khandaker ◽  
Mohammad Robiul Hossan
Keyword(s):  
Cell Adhesion ◽  
Laser System ◽  
Laser Micromachining ◽  
Dermal Fibroblasts ◽  
Air Cooling ◽  
Focal Distance ◽  
Promising Alternative ◽  
System Parameters ◽  
Laser Tube ◽  
Number Of Passes

Laser micromachining technique offers a promising alternative method for rapid production of microfluidic devices. However, the effect of process parameters on the channel geometry and quality of channels on common microfluidic substrates has not been fully understood yet. In this research, we studied the effect of laser system parameters on the microchannel characteristics of Polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA), and microscope glass substrate—three most widely used materials for microchannels. We also conducted a cell adhesion experiment using normal human dermal fibroblasts on laser-machined microchannels on these substrates. A commercial CO2 laser system consisting of a 45W laser tube, circulating water loop within the laser tube and air cooling of the substrate was used for machining microchannels in PDMS, PMMA and glass. Four laser system parameters—speed, power, focal distance, and number of passes were varied to fabricate straight microchannels. The channel characteristics such as depth, width, and shape were measured using a scanning electron microscope (SEM) and a 3D profilometer. The results show that higher speed produces lower depth while higher laser power produces deeper channels regardless of the substrate materials. Unfocused laser machining produces wider but shallower channels. For the same speed and power, PDMS channels were the widest while PMMA channels were the deepest. Results also showed that the profiles of microchannels can be controlled by increasing the number of passes. With an increased number of passes, both glass and PDMS produced uniform, wider, and more circular channels; in contrast, PMMA channels were sharper at the bottom and skewed. In rapid cell adhesion experiments, PDMS and glass microchannels performed better than PMMA microchannels. This study can serve as a quick reference in material-specific laser-based microchannel fabrications.

scholarly journals Effect of Process Parameters and Material Properties on Laser Micromachining of Microchannels

Micromachines ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 123 ◽  
Author(s):  
Matthew Benton ◽  
Mohammad Hossan ◽  
Prashanth Konari ◽  
Sanjeewa Gamagedara
Keyword(s):  
Process Parameters ◽  
Laser System ◽  
Three Dimensional ◽  
Microfluidic Devices ◽  
Scanning Speed ◽  
Transient Heat Conduction ◽  
Laser Micromachining ◽  
Rapid Phase ◽  
Widespread Application ◽  
Optimization Of Process Parameters

Laser micromachining has emerged as a promising technique for mass production of microfluidic devices. However, control and optimization of process parameters, and design of substrate materials are still ongoing challenges for the widespread application of laser micromachining. This article reports a systematic study on the effect of laser system parameters and thermo-physical properties of substrate materials on laser micromachining. Three dimensional transient heat conduction equation with a Gaussian laser heat source was solved using finite element based Multiphysics software COMSOL 5.2a. Large heat convection coefficients were used to consider the rapid phase transition of the material during the laser treatment. The depth of the laser cut was measured by removing material at a pre-set temperature. The grid independent analysis was performed for ensuring the accuracy of the model. The results show that laser power and scanning speed have a strong effect on the channel depth, while the level of focus of the laser beam contributes in determining both the depth and width of the channel. Higher thermal conductivity results deeper in cuts, in contrast the higher specific heat produces shallower channels for a given condition. These findings can help in designing and optimizing process parameters for laser micromachining of microfluidic devices.

Glycoproteins and Cell Adhesion

1975 ◽  
Author(s):  
G. M. W. Cook
Keyword(s):  
Cell Adhesion ◽  
Cell Interaction ◽  
Dermal Fibroblasts ◽  
Membrane Glycoprotein ◽  
Cell Periphery ◽  
Membrane Glycoproteins ◽  
Model Compounds ◽  
Great Economy ◽  
Interaction Phenomena

Over the last decade the importance of glycoproteins at the cell surface has become increasingly evident. The role of surface heterosaccharides in cell interaction phenomena will be discussed in terms of those macromolecules providing the cell with a recognition surface; the carbohydrate groups of membrane glycoproteins may be expected to provide considerable variation in surface structure, with great economy of means, commensurate with the large number of specific interactions which take place at the cell periphery. Evidence for surface glycoproteins being involved in cell adhesion will be briefly reviewed. That adhesive specificity might be incorporated into the arrangement of sugar residues within the carbohydrate groups of surface heterosaccharides which are recognized by an appropriate glycosyltransferase on the surface of apposing cells, with the formation of mutable adhesions will be detailed by reference to recent experimental evidence, obtained with malignant rat dermal fibroblasts. In this type of work the use of exogenous glycoproteins as model compounds has proved useful, however, the need to isolate endogenous membrane glycoprotein acceptors is evident and the results of current work in this area will be described.

scholarly journals Modeling of the Radial Heat Flow and Cooling Processes in a Deep UltravioletCu+Ne-CuBr Laser

2009 ◽  
Vol 2009 ◽  
pp. 1-16
Author(s):  
Iliycho Petkov Iliev ◽  
Snezhana Georgieva Gocheva-Ilieva ◽  
Krassimir Angelov Temelkov ◽  
Nikolay Kirilov Vuchkov ◽  
Nikola Vassilev Sabotinov
Keyword(s):  
Power Density ◽  
Copper Ion ◽  
Nonlinear Boundary Conditions ◽  
Simple Expression ◽  
Air Cooling ◽  
Gas Temperature ◽  
Laser Tube ◽  
Copper Bromide ◽  
Forced Air ◽  
The One

An improved theoretical model of the gas temperature profile in the cross-section of an ultraviolet copper ion excited copper bromide laser is developed. The model is based on the solution of the one-dimensional heat conduction equation subject to special nonlinear boundary conditions, describing the heat interaction between the laser tube and its surroundings. It takes into account the nonuniform distribution of the volume power density along with the radius of the laser tube. The problem is reduced to the boundary value problem of the first kind. An explicit solution of this model is obtained. The model is applied for the evaluation of the gas temperature profiles of the laser in the conditions of free and forced air-cooling. Comparison with other simple models assumed constant volume power density is made. In particular, a simple expression for calculating the average gas temperature is found.

Vascular cell adhesion molecule-1 mediates lymphocyte adherence to cytokine-activated cultured human endothelial cells [published erratum appears in Blood 1990 Dec 1;76(11):2420]

Blood ◽  
1990 ◽  
Vol 76 (5) ◽  
pp. 965-970 ◽  
Author(s):  
TM Carlos ◽  
BR Schwartz ◽  
NL Kovach ◽  
E Yee ◽  
M Rosa ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Adhesion Molecule ◽  
Peripheral Blood ◽  
Cell Adhesion Molecule ◽  
Dermal Fibroblasts ◽  
Enzyme Linked Immunosorbent Assay ◽  
Vascular Cell Adhesion ◽  
Vascular Cell ◽  
Vascular Cell Adhesion Molecule ◽  
Cell Adhesion Molecule 1

The expression and function of a new cytokine-induced endothelial cell adhesion protein, vascular cell adhesion molecule-1 (VCAM-1), was characterized in vitro by using a monoclonal antibody, MoAb 4B9, which recognizes a functional epitope on this protein. As determined by enzyme-linked immunosorbent assay and radioimmunoprecipitation of metabolically labeled cells, VCAM-1 was minimally expressed on unstimulated human umbilical vein endothelium (HUVE), but was rapidly induced by recombinant human tumor necrosis factor-alpha (rhTNF-alpha), rh interleukin-1, and lipopolysaccharide. In contrast to intercellular adhesion molecule-1, VCAM-1 was not induced on dermal fibroblasts or arterial smooth muscle cells after stimulation with rhTNF, or on keratinocytes after stimulation with rh interferon-gamma. MoAb 4B9 significantly inhibited the adherence of peripheral blood lymphocytes (PBL) and lymphocytic cell lines, but not neutrophils, to rhTNF- activated HUVE. The inhibitory effect of MoAb 4B9 on PBL adherence to HUVE was additive to that produced by the CD18 MoAb 60.3. These results show that VCAM-1 mediates a CD18-independent pathway of peripheral blood lymphocyte adherence to cytokine-stimulated HUVE. We propose that lymphocyte binding to VCAM-1, induced on endothelium by cytokines, may be an important component of lymphocyte emigration at sites of inflammation or immune reaction.

scholarly journals Evaluation of Strategies Aimed at Improving Liver Progenitor Cell Rolling and Subsequent Adhesion to the Endothelium

2020 ◽  
Vol 29 ◽  
pp. 096368972091270
Author(s):  
Pierre Edouard Dollet ◽  
Mei Ju Hsu ◽  
Jérôme Ambroise ◽  
Milena Rozzi ◽  
Joachim Ravau ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Cell Adhesion ◽  
Alternative Methods ◽  
Sialyl Lewis X ◽  
Thermosensitive Polymer ◽  
Lewis X ◽  
Promising Alternative ◽  
Sialyl Lewis ◽  
Selectin Ligand

Adult-derived human liver stem/progenitor cells (ADHLSCs) are a promising alternative to orthotopic liver transplantation in the treatment of inborn errors of metabolism. However, as is the case with many mesenchymal stromal cells, ADHLSCs have shown a low level of engraftment, which could be explained by the fact that they lack expression of selectin ligand and LFA-1 and only slightly express VLA- 4, molecules that have been shown to be involved in cell adhesion to the endothelium. In this paper, we have investigated strategies to increase their rolling and adhesion during the homing process by (1) adding a selectin ligand (Sialyl Lewis X) to their surface using biotinyl- N-hydroxy-succinimide–streptavidin bridges, and (2) protecting the adhesion proteins from trypsinization-induced damage using a thermosensitive polymer for cell culture and a nonenzymatic cell dissociation solution (CDS) for harvest. Despite increasing adhesion of ADHLSCs to E-selectin during an adhesion test in vitro performed under shear stress, the addition of Sialyl Lewis X did not increase adhesion to endothelial cells under the same conditions. Cultivating cells on a thermosensitive polymer and harvesting them with CDS increased their adhesion to endothelial cells under noninflammatory conditions, compared to the use of trypsin. However, we were not able to demonstrate any improvement in cell adhesion to the endothelium following culture on polymer and harvest with CDS, suggesting that alternative methods of improving engraftment still need to be evaluated.

scholarly journals Loss of the Desmosomal Component Perp Impairs Wound HealingIn Vivo

2010 ◽  
Vol 2010 ◽  
pp. 1-11 ◽  
Author(s):  
Veronica G. Beaudry ◽  
Rebecca A. Ihrie ◽  
Suzanne B. R. Jacobs ◽  
Bichchau Nguyen ◽  
Navneeta Pathak ◽  
...  
Keyword(s):  
Wound Healing ◽  
Cell Adhesion ◽  
Wound Closure ◽  
Cellular Proliferation ◽  
Dermal Fibroblasts ◽  
Conditional Knockout ◽  
Keratinocyte Proliferation ◽  
Complex Biological Process ◽  
Cell Cell

Epithelial wound closure is a complex biological process that relies on the concerted action of activated keratinocytes and dermal fibroblasts to resurface and close the exposed wound. Modulation of cell-cell adhesion junctions is thought to facilitate cellular proliferation and migration of keratinocytes across the wound. In particular, desmosomes, adhesion complexes critical for maintaining epithelial integrity, are downregulated at the wound edge. It is unclear, however, how compromised desmosomal adhesion would affect wound reepithelialization, given the need for a delicate balance between downmodulating adhesive strength to permit changes in cellular morphology and maintaining adhesion to allow coordinated migration of keratinocyte sheets. Here, we explore the contribution of desmosomal adhesion to wound healing using mice deficient for the desmosomal component Perp. We find thatPerpconditional knockout mice display delayed wound healing relative to controls. Furthermore, we determine that while loss of Perp compromises cell-cell adhesion, it does not impair keratinocyte proliferation and actually enhances keratinocyte migration inin vitroassays. Thus, Perp's role in promoting cell adhesion is essential for wound closure. Together, these studies suggest a role for desmosomal adhesion in efficient wound healing.

Inactivation of Foodborne Pathogens in Milk Using Dynamic High Pressure

2002 ◽  
Vol 65 (2) ◽  
pp. 345-352 ◽  
Author(s):  
J. F. VACHON ◽  
E. E. KHEADR ◽  
J. GIASSON ◽  
P. PAQUIN ◽  
I. FLISS
Keyword(s):  
High Pressure ◽  
Salmonella Enteritidis ◽  
Bacterial Load ◽  
Applied Pressure ◽  
Promising Alternative ◽  
E Coli ◽  
Single Pass ◽  
Cold Pasteurization ◽  
Dynamic High Pressure ◽  
Number Of Passes

Improving the microbiological safety of perishable foods is currently a major preoccupation in the food industry. The aim of this study was to investigate the inactivation of three major food pathogens (Listeria monocytogenes [LSD 105-1], Escherichia coli O157:H7 [ATCC 35150], and Salmonella enterica serotype Enteritidis ATCC [13047]) by dynamic high pressure (DHP) in order to evaluate its potential as a new alternative for the cold pasteurization of milk. The effectiveness of DHP treatment against L. monocytogenes, E. coli O157:H7, and Salmonella Enteritidis was first evaluated in 0.01 M phosphate-buffered saline (PBS) at pH 7.2 as a function of applied pressure (100, 200, and 300 MPa) and of the number of passes (1, 3, and 5) at 25°C. A single pass at 100 MPa produced no significant inactivation of the three pathogens, while increasing the pressure up to 300 MPa or the number of passes to five increased inactivation. From an initial count of 8.3 log CFU/ml, complete inactivation of viable L. monocytogenes was achieved after three successive passes at 300 MPa, while 200-MPa treatments with three and five passes completely eliminated viable Salmonella Enteritidis and E. coli O157:H7, respectively. The effectiveness of DHP for the inactivation of these pathogens was compared to that of hydrostatic high pressure (HHP) using the same pressure (200 MPa, single pass at 25°C). In general, two additional log reductions in viable count were obtained with DHP. DHP was less effective against L. monocytogenes and E. coli O157:H7 in raw milk than in PBS. After five passes at 200 MPa, an 8.3-log reduction was obtained for E. coli O157:H7, while a reduction of about 5.8 log CFU/ml was obtained for L. monocytogenes exposed to 300 MPa for five passes. Exposing milk or buffer samples to mild heating (45 to 60°C) prior to dynamic pressurization enhanced the lethal effect of DHP. The inactivation of pathogens also depended on the initial bacterial concentration. The highest reduction was obtained when the bacterial load did not exceed 105 CFU/ml. In conclusion, DHP was shown to be very effective for the destruction of the tested pathogens. It offers a promising alternative for the cold pasteurization of milk and possibly other liquid foods.

scholarly journals THE INVESTIGATION OF THERMAL LENS PROPERTIES IN THE ACTIVE ELEMENT OF LASER AMPLIFIER WITH HIGH POWER DIODE PUMP

2019 ◽  
Vol 8 ◽  
pp. 3-9
Author(s):  
Gleb Kuptsov ◽  
Alexei Laptev ◽  
Vladimir Petrov ◽  
Victor Petrov ◽  
Efim Pestryakov
Keyword(s):  
Pump Power ◽  
High Power ◽  
Thermal Lens ◽  
Active Element ◽  
Laser System ◽  
Diode Pump ◽  
Average Output ◽  
Focal Distance ◽  
Laser Amplifiers ◽  
Laser Amplification

A femtosecond laser system with a pulse repetition rate up to 1 kHz is being developed at the Institute of Laser Physics of the SB RAS. The key component of the system is the channel of laser amplification based on media doped with Yb3+ ions. The designed average output power of the channel is 300 W. Thermal effects in high-power laser amplifiers are decisive for the parameters of the radiation at the output of system. In this paper the results of experimental measurements of thermal lens focal distance dependence in Yb:YAG active element on diode pump power using geometric method are given. Calculation of the dependence thermal lens focal distance on the power of pump power and a comparison with experimental data are given.

Laser Processing of 2-D and 3-D Structures for Tunable Embedded Capacitors

2011 ◽  
Vol 2011 (DPC) ◽  
pp. 001949-001976
Author(s):  
Rabindra N. Das ◽  
Timothy E. Antesberger ◽  
Francesco Marconi ◽  
Frank D. Egitto ◽  
Mark D. Poliks ◽  
...  
Keyword(s):  
Laser Processing ◽  
High Speed ◽  
Laser System ◽  
Sol Gel ◽  
Single Layer ◽  
Laser Micromachining ◽  
Embedded Capacitors ◽  
Embedded Capacitor ◽  
Material Formulation ◽  
Tunable Device

Material formulation, structuring, and modification are key to increasing the unit volume complexity and density of next generation electronic packaging products. Laser processing is finding an increasing number of applications in the fabrication of these advanced microelectronic devices. This is due, in part, to the ability to achieve highly localized treatment of materials with a spatial resolution of tens of microns. In addition, the process is data-driven, that is, patterns can be generated without the need for masking materials. In the present investigation, a variety of structures have been generated in polymer nanocomposites, nanoparticle films, and sol-gel thin films using a computer-controlled laser system. Specifically, micromachining technology has been used to produce both variable-thickness and discrete capacitors from a single sheet (layer) of capacitor material, such that both types of structures can be integrated into the same layer. In addition, the laser micromachining technology has been extended to design and develop new vertical multilayer embedded capacitors for high speed applications. High speed packages require thick dielectrics. Calculations show that multilayer vertical capacitors can be better than thick capacitors formed from a single layer. In general, multilayer embedded capacitors are fabricated by repeated lamination of resin-coated copper, or pre-preg with a capacitor core. This is a time consuming, lengthy process. As an alternative, we have deposited a single, thick capacitance layer, and subsequent laser micromachining has been used to form multiple parallel channels of a controlled depth. Metal deposition in the channels results in a multilayer embedded capacitor structure. Lasers micromaching can also provide various complex patterns such as 3-D spiral channels within a dielectric or magnetically active nanocomposite, subsequently filled with conducting materials to form inductors. This technique can be used to prepare inductors and capacitors in the same layer of nanocomposite material. Hence, the technique can be used to generate multi-functional structures for tunable device applications.

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