scholarly journals Mechanism of biosurfactant adsorption to oil/water interfaces from millisecond scale tensiometry measurements

2017 ◽  
Vol 7 (6) ◽  
pp. 20170013 ◽  
Author(s):  
Lingling Kong ◽  
Kadi Liis Saar ◽  
Raphael Jacquat ◽  
Liu Hong ◽  
Aviad Levin ◽  
...  
Keyword(s):  
Interfacial Tension ◽  
Microfluidic Channel ◽  
Industrial Applications ◽  
Droplet Microfluidics ◽  
Kinetic Measurements ◽  
Alkyl Benzene Sulfonate ◽  
Cyclic Lipopeptide ◽  
Ability To Act ◽  
Adsorption Processes ◽  
Order Of Magnitude

Many biological molecules are by their nature amphiphilic and have the ability to act as surfactants, stabilizing interfaces between aqueous and immiscible oil phases. In this paper, we explore the adsorption kinetics of surfactin, a naturally occurring cyclic lipopeptide, at hexadecane/water interfaces and compare and contrast its adsorption behaviour with that of synthetic alkyl benzene sulfonate isomers, through direct measurements of changes in interfacial tension upon surfactant adsorption. We access millisecond time resolution in kinetic measurements by making use of droplet microfluidics to probe the interfacial tension of hexadecane droplets dispersed in a continuous water phase through monitoring their deformation when the droplets are exposed to shear flows in a microfluidic channel with regular corrugations. Our results reveal that surfactin rapidly adsorbs to the interface, thus the interfacial tension equilibrates within 300 ms, while the synthetic surfactants used undergo adsorption processes at an approximately one order of magnitude longer timescale. The approach presented may provide opportunities for understanding and modulating the adsorption mechanism of amphiphiles on a variety of interfaces in the context of life sciences and industrial applications.

scholarly journals Helmet Phthalocyaninato Iron Complex as a Primary Drier for Alkyd Paints

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1220
Author(s):  
Jan Honzíček ◽  
Eliška Matušková ◽  
Štěpán Voneš ◽  
Jaromír Vinklárek
Keyword(s):  
Catalytic Performance ◽  
Mechanical Tests ◽  
Iron Complex ◽  
Kinetic Measurements ◽  
Time Resolved ◽  
Strong Activity ◽  
Vis Spectroscopy ◽  
Order Of Magnitude ◽  
Transparent Coatings ◽  
Time Resolved Infrared Spectroscopy

This study describes the catalytic performance of an iron(III) complex bearing a phthalocyaninato-like ligand in two solvent-borne and two high-solid alkyd binders. Standardized mechanical tests revealed strong activity, which appeared in particular cases at concentrations about one order of magnitude lower than in the case of cobalt(II) 2-ethylhexanoate, widespread used in paint-producing industry. The effect of the iron(III) compound on autoxidation process, responsible for alkyd curing, was quantified by kinetic measurements by time-resolved infrared spectroscopy and compared with several primary driers. Effect of the drier concentration on coloration of transparent coatings was determined by UV–Vis spectroscopy.

scholarly journals Interfacial Tension Measurements in Microfluidic Quasi-Static Extensional Flows

Micromachines ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 272
Author(s):  
Doojin Lee ◽  
Amy Q. Shen
Keyword(s):  
Interfacial Tension ◽  
Microfluidic Device ◽  
Extensional Flow ◽  
Immiscible Fluids ◽  
Droplet Microfluidics ◽  
Channel Height ◽  
Deformation Model ◽  
Droplet Deformation ◽  
Extensional Flows ◽  
2D Model

Droplet microfluidics provides a versatile tool for measuring interfacial tensions between two immiscible fluids owing to its abilities of fast response, enhanced throughput, portability and easy manipulations of fluid compositions, comparing to conventional techniques. Purely homogeneous extension in the microfluidic device is desirable to measure the interfacial tension because the flow field enables symmetric droplet deformation along the outflow direction. To do so, we designed a microfluidic device consisting of a droplet production region to first generate emulsion droplets at a flow-focusing area. The droplets are then trapped at a stagnation point in the cross junction area, subsequently being stretched along the outflow direction under the extensional flow. These droplets in the device are either confined or unconfined in the channel walls depending on the channel height, which yields different droplet deformations. To calculate the interfacial tension for confined and unconfined droplet cases, quasi-static 2D Darcy approximation model and quasi-static 3D small deformation model are used. For the confined droplet case under the extensional flow, an effective viscosity of the two immiscible fluids, accounting for the viscosity ratio of continuous and dispersed phases, captures the droplet deformation well. However, the 2D model is limited to the case where the droplet is confined in the channel walls and deforms two-dimensionally. For the unconfined droplet case, the 3D model provides more robust estimates than the 2D model. We demonstrate that both 2D and 3D models provide good interfacial tension measurements under quasi-static extensional flows in comparison with the conventional pendant drop method.

scholarly journals Sorting by interfacial tension (SIFT): Label-free enzyme sorting using droplet microfluidics

2019 ◽  
Vol 1089 ◽  
pp. 108-114 ◽  
Author(s):  
Daniel G. Horvath ◽  
Samuel Braza ◽  
Trevor Moore ◽  
Ching W. Pan ◽  
Lailai Zhu ◽  
...  
Keyword(s):  
Interfacial Tension ◽  
Droplet Microfluidics ◽  
Free Enzyme ◽  
Label Free

scholarly journals Anomalous hydrogen evolution behavior in high-pH environment induced by locally generated hydronium ions

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Xuesi Wang ◽  
Chaochen Xu ◽  
Mietek Jaroniec ◽  
Yao Zheng ◽  
Shi-Zhang Qiao
Keyword(s):  
Hydrogen Evolution ◽  
Hydrogen Adsorption ◽  
Water Dissociation ◽  
In Situ Raman Spectroscopy ◽  
Kinetic Measurements ◽  
High Ph ◽  
Hydronium Ions ◽  
Adsorption Processes ◽  
Bulk Model ◽  
Evolution Behavior

Abstract Most fundamental studies of electrocatalysis are based on the experimental and simulation results obtained for bulk model materials. Some of these mechanistic understandings are inapplicable for more active nanostructured electrocatalysts. Herein, considering the simplest and most typical electrocatalytic process, the hydrogen evolution reaction, an alternative reaction mechanism is proposed for nanomaterials based on the identification of a new intermediate, which differs from those commonly known for the bulk counterparts. In-situ Raman spectroscopy and electrochemical thermal/kinetic measurements were conducted on a series of nanomaterials under different conditions. In high-pH electrolytes with negligible hydronium (H3O+) concentration in bulk phase, massive H3O+ intermediates are found generating on the catalytic surface during water dissociation and hydrogen adsorption processes. These H3O+ intermediates create a unique acid-like local reaction environment on nanostructured catalytic surfaces and cut the energy barrier of the overall reaction. Such phenomena on nanostructured electrocatalysts explain their widely observed anomalously high activity under high-pH conditions.

The Effects of Graphene Oxide and Partially Reduced Graphene Oxide on the Enzymatic Activity of Microbial Transglutaminase in Gelatin

MRS Advances ◽  
2019 ◽  
Vol 4 (15) ◽  
pp. 879-887
Author(s):  
Rebecca Isseroff ◽  
Jerry Reyes ◽  
Roshan Reddy ◽  
Nicholas Williams ◽  
Miriam Rafailovich
Keyword(s):  
Graphene Oxide ◽  
Enzymatic Activity ◽  
Enzymatic Catalysis ◽  
Gelation Time ◽  
Crosslinking Density ◽  
Industrial Applications ◽  
Microbial Transglutaminase ◽  
Water Mixture ◽  
Gelatin Solution ◽  
Order Of Magnitude

ABSTRACTA significant drawback of enzyme use in industrial applications is its lack of stability. Graphene oxide (GO) has previously been investigated for enzyme immobilization and enhancement of enzymatic catalysis. Microbial transglutaminase (MTG) is an enzyme that is used to modify food proteins, increase durability of textiles, and crosslink hydrogels for drug delivery. We tested the effects of adding GO and partially reduced GO (pRGO) to water solutions of gelatin and then crosslinking it with MTG, measuring both the resulting gelatin modulus and then the time it took for the onset of gelation. We found that the presence of pRGO in a gelatin-MTG-water mixture (when using 0.75 g MTG in 10 ml of gelatin solution) significantly increases the modulus by 60% more than the control. Using this same concentration of MTG, we measured the onset of gelation time and found that pRGO in gelatin solution reduces the onset of gelation time by nearly 50% while inducing a very large increase in viscosity by three orders of magnitude, whereas the addition of GO increases the onset of gelation time by 33% and decreases the viscosity of the gel by more than one order of magnitude. The very large enhancement by pRGO of the viscosity may be due to pRGO’s electron withdrawing ability and/or may also be due to adsorption of gelatin to the pRGO platelets which effectively increases the crosslinking density through non-enzymatic processes assisting the enzymatic activity.

scholarly journals Dual sequentially addressable dielectrophoretic array for high-throughput, scalable, multiplexed droplet sorting

2021 ◽  
Vol 25 (4) ◽  
Author(s):  
Akihiro Isozaki ◽  
Dunhou Huang ◽  
Yuta Nakagawa ◽  
Keisuke Goda
Keyword(s):  
High Throughput ◽  
Cell Biology ◽  
Digital Pcr ◽  
Industrial Applications ◽  
Droplet Microfluidics ◽  
Diverse Range ◽  
Droplet Sorting ◽  
On Chip ◽  
Single Droplets

AbstractDroplet microfluidics is a powerful tool for a diverse range of biomedical and industrial applications such as single-cell biology, synthetic biology, digital PCR, biosafety monitoring, drug screening, and food, feed, and cosmetic industries. As an integral part of droplet microfluidics, on-chip multiplexed droplet sorting has recently gained enthusiasm, since it enables real-time sorting of single droplets containing cells with different phenotypes into multiple bins. However, conventional sorting methods are limited in throughput and scalability. Here, we present high-throughput, scalable, multiplexed droplet sorting by employing a pair of sequentially addressable dielectrophoretic arrays (SADAs) across a microchannel on a microfluidic chip. A SADA is an on-chip array of electrodes, each of which is sequentially activated and deactivated in synchronization to the position and speed of a flowing droplet of interest. The dual-SADA (dSADA) structure enables high-throughput deflection of droplets in multiple directions in a well-controlled manner. For proof-of-concept demonstration and characterization of the dSADA, we performed fluorescence-activated droplet sorting (FADS) with a 3-way dSADA at a high throughput of 2450 droplets/s. Furthermore, to show the scalability of the dSADA, we also performed FADS with a 5-way dSADA at a high throughput of 473 droplets/s.

scholarly journals Spatiotemporal periodicity of dislocation dynamics in a two-dimensional microfluidic crystal flowing in a tapered channel

2016 ◽  
Vol 113 (43) ◽  
pp. 12082-12087 ◽  
Author(s):  
Ya Gai ◽  
Chia Min Leong ◽  
Wei Cai ◽  
Sindy K. Y. Tang
Keyword(s):  
Solid Mechanics ◽  
Microfluidic Channel ◽  
Deformation Mode ◽  
Dislocation Nucleation ◽  
Point Of View ◽  
Droplet Microfluidics ◽  
Dislocation Dynamics ◽  
Periodic Patterns ◽  
And Migration ◽  
Tapered Channel

When a many-body system is driven away from equilibrium, order can spontaneously emerge in places where disorder might be expected. Here we report an unexpected order in the flow of a concentrated emulsion in a tapered microfluidic channel. The velocity profiles of individual drops in the emulsion show periodic patterns in both space and time. Such periodic patterns appear surprising from both a fluid and a solid mechanics point of view. In particular, when the emulsion is considered as a soft crystal under extrusion, a disordered scenario might be expected based on the stochastic nature of dislocation dynamics in microscopic crystals. However, an orchestrated sequence of dislocation nucleation and migration is observed to give rise to a highly ordered deformation mode. This discovery suggests that nanocrystals can be made to deform more controllably than previously thought. It can also lead to novel flow control and mixing strategies in droplet microfluidics.

Ultra-High Frequency Sound Waves for Microparticle Separation

2015 ◽  
Author(s):  
Ghulam Destgeer ◽  
Anas Alazzam ◽  
Hyung Jin Sung
Keyword(s):  
Acoustic Waves ◽  
High Frequency ◽  
Surface Acoustic Waves ◽  
Microfluidic Channel ◽  
Sound Waves ◽  
Ultra High Frequency ◽  
High Frequency Sound ◽  
Frequency Sound ◽  
Sheath Fluid ◽  
Order Of Magnitude

In this study, we have demonstrated a particle separation device taking advantage of the ultra-high frequency sound waves. The sound waves, in the form of surface acoustic waves, are produced by an acoustofluidic platform build on top of a piezoelectric substrate bonded to a microfluidic channel. The particles’ mixture, pumped through the microchannel, is focused using a sheath fluid. A travelling surface acoustic wave (TSAW), propagating normal to the flow, interacts with the particles and deflect them from their original path to induce size-based separation in a continuous flow. We initially started the experiment with 40 MHz TSAWs for deflecting 10 μm diameter polystyrene particles but failed. However, larger diameter particles (∼ 30 μm) were successfully deflected from their streamlines and separated from the smaller particles (∼ 10 μm) using TSAWs with 40 MHz frequency. The separation of smaller diameter particles (3, 5 and 7 μm) was also achieved using an order of magnitude higher-frequency (∼ 133 MHz) TSAWs.

scholarly journals Effect of Surface and Interfacial Tension on the Resonance Frequency of Microfluidic Channel Cantilever

Sensors ◽  
2020 ◽  
Vol 20 (22) ◽  
pp. 6459
Author(s):  
Rosmi Abraham ◽  
Faheem Khan ◽  
Syed A. Bukhari ◽  
Qingxia Liu ◽  
Thomas Thundat ◽  
...  
Keyword(s):  
Interfacial Tension ◽  
Resonance Frequency ◽  
Laser Doppler Vibrometer ◽  
Microfluidic Channel ◽  
Interface Tension ◽  
Near Surface ◽  
Surface And Interface ◽  
Interface Layers ◽  
Extra Stress ◽  
Effect Of Surface

The bending resonance of micro-sized resonators has been utilized to study adsorption of analyte molecules in complex fluids of picogram quantity. Traditionally, the analysis to characterize the resonance frequency has focused solely on the mass change, whereas the effect of interfacial tension of the fluid has been largely neglected. By observing forced vibrations of a microfluidic cantilever filled with a series of alkanes using a laser Doppler vibrometer (LDV), we studied the effect of surface and interfacial tension on the resonance frequency. Here, we incorporated the Young–Laplace equation into the Euler–Bernoulli beam theory to consider extra stress that surface and interface tension exerts on the vibration of the cantilever. Based on the hypothesis that the near-surface region of a continuum is subject to the extra stress, thin surface and interface layers are introduced to our model. The thin layer is subject to an axial force exerted by the extra stress, which in turn affects the transverse vibration of the cantilever. We tested the analytical model by varying the interfacial tension between the silicon nitride microchannel cantilever and the filled alkanes, whose interfacial tension varies with chain length. Compared with the conventional Euler–Bernoulli model, our enhanced model provides a better agreement to the experimental results, shedding light on precision measurements using micro-sized cantilever resonators.

The Laboratory Research on Ultra-Low Interfacial Tension Foam Flooding System with High-Temperature and High-Salinity

2011 ◽  
Vol 71-78 ◽  
pp. 2163-2168 ◽  
Author(s):  
Xin Liang ◽  
Ming Hui Xiang ◽  
Yong Yang ◽  
Qi Hua Chen ◽  
Zeng Rong Shu
Keyword(s):  
High Temperature ◽  
Interfacial Tension ◽  
High Salinity ◽  
Divalent Cations ◽  
Laboratory Research ◽  
Foam Properties ◽  
Order Of Magnitude ◽  
Low Interfacial Tension ◽  
Foam Flooding ◽  
Mixture System

To obtain the ultra-low interfacial tension foam flooding system for the real reservoir condition of high-temperature and high-salinity, foam properties and dynamic interfacial tension had been performed by Ross-miles test and spin drop tension meter respectively. Ten types of surfactants were screened by foamability, stability and interfacial tension (IFT) at 85°C, high-salinity with 800 mg/L divalent cations and 30000 mg/L total mineralization. The AOS, AESO and 20YB were selected to compose further anion-nonionic mixture system. Due to AOS had excellent foam properties, AESO could achieve low interfacial tension and 20YB could improve the film quality. Through series complex study, the ultra-low interfacial tension (10-4 mN/m order of magnitude) foam system was obtained with the composition of 0.15% wt AOS+0.15% wt AESO+0.11%~0.012% wt 20YB for high-temperature and high-salinity, which V foam was 240-235 mL and t 0.5 was 180-190 min. In addition, the synergistic effect of these surfactants had been described.

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