scholarly journals Closable Valves and Channels for Polymeric Microfluidic Devices

Micromachines ◽  
2020 ◽  
Vol 11 (7) ◽  
pp. 627 ◽  
Author(s):  
Charles Clark ◽  
M. Woolf ◽  
Sarah Karstens ◽  
Hannah Lewis ◽  
Aeren Nauman ◽  
...  
Keyword(s):  
Polyurethane Foam ◽  
Direct Contact ◽  
Microfluidic Devices ◽  
Cross Contamination ◽  
Unit Operation ◽  
Analytical Measurement ◽  
Precise Control ◽  
Contact Heating ◽  
Fluidic Control ◽  
Liquid Movement

This study explores three unique approaches for closing valves and channels within microfluidic systems, specifically multilayer, centrifugally driven polymeric devices. Precise control over the cessation of liquid movement is achieved through either the introduction of expanding polyurethane foam, the application of direct contact heating, or the redeposition of xerographic toner via chloroform solvation and evaporation. Each of these techniques modifies the substrate of the microdevice in a different way. All three are effective at closing a previously open fluidic pathway after a desired unit operation has taken place, i.e., sample metering, chemical reaction, or analytical measurement. Closing previously open valves and channels imparts stringent fluidic control—preventing backflow, maintaining pressurized chambers within the microdevice, and facilitating sample fractionation without cross-contamination. As such, a variety of microfluidic bioanalytical systems would benefit from the integration of these valving approaches.

Direct contact heating for hot forming die quenching

2016 ◽  
Vol 98 ◽  
pp. 1165-1173 ◽  
Author(s):  
J.N. Rasera ◽  
K.J. Daun ◽  
C.J. Shi ◽  
M. D'Souza
Keyword(s):  
Direct Contact ◽  
Hot Forming ◽  
Die Quenching ◽  
Contact Heating

Direct Contact Heating for Hot Forming Die Quenching

2014 ◽  
Author(s):  
J. N. Rasera ◽  
K. J. Daun ◽  
M. D’Souza
Keyword(s):  
Yield Strength ◽  
Material Characterization ◽  
Direct Contact ◽  
Hot Forming ◽  
Boron Steel ◽  
Martensitic Structure ◽  
Austenitizing Temperature ◽  
Contact Heating ◽  
Heating Technology ◽  
Roller Hearth

Most hot forming lines use slow, energy-intensive roller hearth furnaces to austenitize boron steel “blanks”. This paper describes an alternative heating technology in which blanks are austenitized by bringing them into contact with a hot monolith. The austenitizing temperature was reached in less than 30 seconds, and subsequent material characterization tests on oil-quenched blanks confirm that a fully martensitic structure is formed, and that the hardness and yield strength are comparable to furnace-treated samples. An Al-Si coating is typically used to prevent the oxidation and decarburization of the blanks within the furnace; preliminary tests found that the coating adheres to the monolith, impeding blank transfer and damaging the Al-Si-Fe ternary coating. Five interchangeable striking surfaces were assessed to see if they were less prone to adhering to the molten Al-Si coating.

SIZE-CONTROLLED DROPLET GENERATION IN A MICROFLUIDIC DEVICE FOR RARE DNA AMPLIFICATION BY OPTIMIZING ITS EFFECTIVE PARAMETERS

2018 ◽  
Vol 18 (01) ◽  
pp. 1850002 ◽  
Author(s):  
ALI LASHKARIPOUR ◽  
ALI ABOUEI MEHRIZI ◽  
MASOUD GOHARIMANESH ◽  
MOHAMMADREZA RASOULI ◽  
SAJAD RAZAVI BAZAZ
Keyword(s):  
Single Molecule ◽  
Dominant Role ◽  
Dna Amplification ◽  
Microfluidic Devices ◽  
Sample Volume ◽  
Droplet Generation ◽  
Droplet Radius ◽  
Generation Process ◽  
Effective Parameters ◽  
Precise Control

Versatility and portability of microfluidic devices play a dominant role in their widespread use by researchers. Droplet-based microfluidic devices have been extensively used due to their precise control over sample volume, and ease of manipulating and addressing each droplet on demand. Droplet-based polymerase chain reaction (PCR) devices are particularly desirable in single DNA amplification. If the droplets are small enough to contain only one DNA molecule, single molecule amplification becomes possible, which can be advantageous in several cases such as early cancer detection. In this work, flow-focusing microfluidic droplet generation’s parameters are numerically investigated and optimized for generating the smallest droplet possible, while considering fabrication limits. Taguchi design of experiment method is used to study the effects of key parameters in droplet generation. By exploiting this approach, a droplet with a radius of 111[Formula: see text]nm is generated using a 3[Formula: see text][Formula: see text]m orifice. Since the governing physics of the droplet generation process is not totally understood yet, by means of analysis of variance (ANOVA) analysis, a generalized linear model (GLM) is proposed to predict the droplet radius, given the values of eight major parameters affecting the droplet size. The proposed model shows a correlation of 95.3% and 64.95% for droplets of radius greater than and lower than 5[Formula: see text][Formula: see text]m, respectively. Finally, the source of this variation of behavior in different size scales is identified.

scholarly journals Microbial Profile of Dawadawa Vended in Tamale Central Market

2021 ◽  
Author(s):  
Dorcas M Hallo ◽  
Abudu Ballu Duwiejuah ◽  
Zita Naangmenyele ◽  
Abubakari Z Imoro ◽  
Gernard Quarcoo ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
West Africa ◽  
Human Skin ◽  
Direct Contact ◽  
Sampling Technique ◽  
Cross Contamination ◽  
E Coli ◽  
Microbial Profile ◽  
High Prevalence ◽  
Handling Practices

Abstract Background: Dawadawa is a common spice used in most rural homes across West Africa to spike the protein source in meals. This study assessed the handling practices of vendors and the microbial load of dawadawa vended in the Tamale Central Market. Methods: A total of 15 samples were collected from 5 sections of the market using the random stratified sampling technique. Results: Out of the 15 samples collected, 8 samples (53.33%) had Salmonella spp, 1 sample (6.67%) had E. coli and all 15 samples (100%) had Staphylococcus aureus. Conclusions: Samples covered recorded no count of Salmonella spp and E. coli but high counts for Staphylococcus aureus. Factors accounting for the high prevalence of Staphylococcus aureus might be cross-contamination associated with improper handling practices as the human skin is known to be a reservoir of Staphylococcus aureus. Hence, the need for vendors to package dawadawa in neat disposal packs to reduce direct contact.

Direct Contact Heating of Fermentors by Rotational Hot Gas Discharge System

2002 ◽  
Author(s):  
Yutaka Kitamura ◽  
Tung Liang ◽  
Dan Paquin ◽  
Loren Gautz
Keyword(s):  
Direct Contact ◽  
Gas Discharge ◽  
Discharge System ◽  
Hot Gas ◽  
Contact Heating

P–153 Comparison outcome of vitrified human embryos stored in vapor phase liquid nitrogen (LN2) and direct LN2

2021 ◽  
Vol 36 (Supplement_1) ◽  
Author(s):  
E A Park ◽  
K Y Kang ◽  
J H Lee ◽  
J Y Lee ◽  
H S Kim ◽  
...  
Keyword(s):  
Clinical Outcomes ◽  
Vapor Phase ◽  
Direct Contact ◽  
Survival Rates ◽  
Human Embryos ◽  
Cross Contamination ◽  
Long Term Storage ◽  
Full Development ◽  
Term Storage

Abstract Study question Is vapor cryopreserved LN2 storage beneficial for clinical outcomes of vitrified human embryos that are frozen compared to vitrified human embryos having direct contact with LN2. Summary answer There are no significant differences compared to clinical outcomes of human embryos stored in LN2 vapor and direct store in LN2. What is known already There has been concerned about potential cross-contamination and biohazard issues of embryos for long term storage using direct LN2. This study aimed to compare clinical outcomes of human embryos transfer between vapor phase and liquid LN2. Study design, size, duration The embryo has undergone vitrification for long term storage with vapor or direct contact in LN2. After the thawing of the embryo, we checked on the survival rates. We transferred only one or two embryos per patient and kept analyzing the implantation and pregnancy rates Participants/materials, setting, methods This retrospective study was carried out from January 2018 to December 2019 with 3272cycles 4713embryos; vitrified for long term storage in vapor phase or direct contact with LN2. We compared the clinical outcomes of frozen embryo transfer cycles using vitrified for long term storage in vapor phase and direct contact with LN2. Clinical outcomes monitored were embryo survival, subsequent implantation and pregnancy after single or double embryo transfer Main results and the role of chance A total of 4713 fertilized human embryos are vitrified and then stored in LN2 vapor (n = 2520 cycles) or direct contact LN2 (n = 752 cycles). The study showed that the blastocyst stored in vapor able to retain full development. Survival was 97.8% (vapor) and 97.6% (direct contact LN2), and the vapor storage of human embryos had no significant difference in survival rates after a long term storage. For single blastocyst transfer, pregnancy and implantation rates were 51.5%, 52.4% in vapor, 54.6%, 54.9% in direct LN2; respectively (p=NS). In double blastocyst transfer, the pregnancy and implantation rates were 61.8%, 42.0% in vapor and 64.7%, 44.5% in direct LN2; respectively (p=NS). There were also no significant differences between two groups. Limitations, reasons for caution The study showed that the blastocyst stored in vapor can retain full development. A vapor storage system thus is safe and effective for long term vapor storage of vitrified human embryos.Within the limits of this study, there was no detection of an adverse effect of vapor storage. Wider implications of the findings: Vapor storage systems thus represent a useful alternative for safe and effective long-term storage of vitrified human embryos that can avoid cross contamination chances from having direct contact with LN2. Trial registration number Not applicable

Investigation of Automated Cell Manipulation in Optical Tweezers-Assisted Microfluidic Chamber Using Simulations

2011 ◽  
Author(s):  
Sagar Chowdhury ◽  
Petr Svec ◽  
Chenlu Wang ◽  
Kevin T. Seale ◽  
John P. Wikswo ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Optical Tweezers ◽  
High Precision ◽  
High Throughput ◽  
Microfluidic Devices ◽  
Cell Manipulation ◽  
Precise Control ◽  
Biological Objects ◽  
Microfluidic Chamber ◽  
Manipulation Process

Microfluidic devices are well suited for the study of biological objects because of their indirect nature of manipulation and high throughput. However, the cell manipulation process solely depends on the fluid flow and hence precise control is difficult to attain inside a microfluidic chamber. Utilizing optical tweezers as a complementary tool provides precise manipulation control. We have presented an automated cell manipulation approach using optical tweezers operating inside a microfluidic chamber. To test and demonstrate the effectiveness of the approach we have developed a physics-based simulator that is completely automated and allows high precision of manipulation.

Technical Note: Comparison of the Sound Insulation of Lightweight Partitions with Different Sound Absorbing Infills

2002 ◽  
Vol 9 (4) ◽  
pp. 303-309 ◽  
Author(s):  
Jose Maria Bravo ◽  
Hermelando Estelles ◽  
Jaime Llinares ◽  
Jaime Sinisterra ◽  
Antonio Uris
Keyword(s):  
Polyurethane Foam ◽  
Direct Contact ◽  
Technical Note ◽  
High Flow ◽  
Sound Insulation ◽  
Gypsum Board ◽  
Measurement Results ◽  
Absorbing Materials ◽  
Flow Resistivity ◽  
Sound Reduction

Measurements of sound reduction indices for lightweight gypsum board partitions filled with three different sound absorbing materials (rockwool, glasswool and polyurethane foam) are reported. For partitions where the gypsum panels are mounted on a common stud, with the sound absorbing infill in direct contact with both panels and for uncoupled double partitions, measurement results show that polyurethane foam, of high flow resistivity and stiffness, is less effective as an infill than either rockwool or glasswool.

Microfluidic Cell Co-Culture Platform With Liquid Fluorocarbon as the Cell Separator

2012 ◽  
Author(s):  
Bryson M. Brewer ◽  
Mingjian Shi ◽  
Yandong Gao ◽  
Donna J. Webb ◽  
Jon F. Edd ◽  
...  
Keyword(s):  
Low Cost ◽  
Specific Treatment ◽  
Microfluidic Devices ◽  
Cellular Communication ◽  
Cell Populations ◽  
Cell Type ◽  
Physical Damage ◽  
Precise Control ◽  
Distinct Cell ◽  
Cell Processes

Cell co-culture platforms are essential tools for investigating inter-cellular communication and cellular activities among different cell populations. Microfluidic cell co-culture platforms offer several advantages over their conventional counterparts, including precise control over the cellular microenvironment, low cost, and high throughput. Previously, we have developed microfluidic devices using a hydraulically/pneumatically controlled polydimethylsiloxane (PDMS) valve barrier to separate distinct cell populations in culture, providing a means for manipulation and specific treatment of each cell type with different reagents [1]. After releasing the barrier, different cell populations can interact with each other while being observed using real-time imaging. However, the solid PDMS valve barrier is not truly reversible, as any cells/cell processes underneath the barrier will likely undergo physical damage when the valve barrier is activated.

scholarly journals Reduction of SARS-CoV-2 Infectious Titers by Direct Contact with Cuprous-Oxide Impregnated Face Masks External Layers

2021 ◽  
Vol 07 (08) ◽  
Author(s):  
Wei Xu ◽  
Keyword(s):  
General Population ◽  
Cuprous Oxide ◽  
Direct Contact ◽  
Nonwoven Fabric ◽  
Cross Contamination ◽  
Increased Risk ◽  
Significant Difference ◽  
Filtration Properties

SARS-CoV-2 can remain viable on the protective face masks surface for several days. Mask touching, reuse and disposal occurs frequently, leading to increased risk of cross-contamination, infection and further transmission. Cuprous-oxide has potent virucidal properties. We determined the capacity of surgical face masks (type IIR) made with nonwoven fabric impregnated with cuprous-oxide microparticles (Test Fabric), to inactivate SARS-CoV-2 when in direct contact with the virus. The Test Fabric reduced the infectious titers of SARS-CoV-2 by 0.73, 3.02 and 4.19 log10 within 5, 30 and 60 minutes, respectively. In contrast, the infectious titers of the virus were reduced by Control Fabric by 0.24, 0.67 and 0.97 within 5, 30 and 60 minutes, respectively. The reductions were significantly higher in the Test Fabric than in the Control Fabric (0.49, 2.35 and 3.22 log difference, accordingly), reaching a statistically significant difference after 5 minutes (p<0.01). The mask filtration properties were not affected by the presence of the cuprous oxide microparticles. We conclude that the use of cuprous-oxide containing face masks in the external layers of respiratory face masks may significantly reduce the risk of SARS-CoV-2 cross-contamination, transmission and infection, due to masks handling and disposal, especially when used by the general population.

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