285 research outputs found
Forced generation of simple and double emulsions in all-aqueous system
We report an easy-to-implement method that allows the direct generation of
water-in-water (w/w) single emulsions. The method relies on direct perturbation
of the pressure that drives the flow of the dispersed phase of the emulsions.
The resultant inner jet is induced to break up into droplets due to the growth
of the perturbation through Rayleigh-Plateau instability [L. Rayleigh, Proc. R.
Soc. London 29, 71-97 (1879)]; this leads to the formation of monodisperse
droplets. By implementing this method on a modified microfluidic device, we
directly generate water-in-water-in-water (w/w/w) double emulsions with good
control over the size and the number of encapsulated droplets. Our approach
suggests a new route to apply droplet-based microfluidics to completely
water-based systems
Fluctuation-induced dynamics of multiphase liquid jets with ultra-low interfacial tension
Control of fluid dynamics at the micrometer scale is essential to emulsion
science and materials design, which is ubiquitous in everyday life and is
frequently encountered in industrial applications. Most studies on multiphase
flow focus on oil-water systems with substantial interfacial tension. Advances
in microfluidics have enabled the study of multiphase flow with more complex
dynamics. Here, we show that the evolution of the interface in a jet surrounded
by a co-flowing continuous phase with an ultra-low interfacial tension presents
new opportunities to the control of flow morphologies. The introduction of a
harmonic perturbation to the dispersed phase leads to the formation of
interfaces with unique shapes. The periodic structures can be tuned by
controlling the fluid flow rates and the input perturbation; this demonstrates
the importance of the inertial effects in flow control at ultra-low interfacial
tension. Our work provides new insights into microfluidic flows at ultra-low
interfacial tension and their potential applications
Mechanical compression to characterize the robustness of liquid marbles
In this work, we have devised a new approach to measure the critical pressure that a liquid marble can withstand. A liquid marble is gradually squeezed under a mechanical compression applied by two parallel plates. It ruptures at a sufficiently large applied pressure. Combining the force measurement and the high-speed imaging, we can determine the critical pressure that ruptures the liquid marble. This critical pressure, which reflects the mechanical robustness of liquid marbles, depends on the type and size of the stabilizing particles as well as the chemical nature of the liquid droplet. By investigating the surface of the liquid marble, we attribute its rupture under the critical pressure to the low surface coverage of particles when highly stretched. Moreover, the applied pressure can be reflected by the inner Laplace pressure of the liquid marble considering the squeezing test is a quasi-static process. By analyzing the Laplace pressure upon rupture of the liquid marble, we predict the dependence of the critical pressure on the size of the liquid marble, which agrees well with experimental results
Coalescence of electrically charged liquid marbles
© The Royal Society of Chemistry. In this work, we investigated the coalescence of liquid water marbles driven by a DC electric field. We have found that two contacting liquid marbles can be forced to coalesce when they are charged by a sufficiently high voltage. The threshold voltage leading to the electro-coalescence sensitively depends on the stabilizing particles as well as the surface tension of the aqueous phase. By evaluating the electric stress and surface tension effect, we attribute such coalescence to the formation of a connecting bridge driven by the electric stress. This liquid bridge subsequently grows and leads to the merging of the marbles. Our interpretation is confirmed by the scaling relation between the electric stress and the restoring capillary pressure. In addition, multiple marbles in a chain can be driven to coalesce by a sufficiently high threshold voltage that increases linearly with the number of the marbles. We have further proposed a simple model to predict the relationship between the threshold voltage and the number of liquid marbles, which agrees well with the experimental results. The concept of electro-coalescence of liquid marbles can be potentially useful in their use as containers for chemical and biomedical reactions involving multiple reagents
Corrugated interfaces in multiphase core-annular flow
Microfluidic devices can be used to produce highly controlled and
monodisperse double or multiple emulsions. The presence of inner drops inside a
jet of the middle phase introduces deformations in the jet, which leads to
breakup into monodisperse double emulsions. However, the ability to generate
double emulsions can be compromised when the interfacial tension between the
middle and outer phases is low, leading to flow with high capillary and Weber
numbers. In this case, the interface between the fluids is initially deformed
by the inner drops but the jet does not break into drops. Instead, the jet
becomes highly corrugated, which prevents formation of controlled double
emulsions. We show using numerical calculations that the corrugations are
caused by the inner drops perturbing the interface and the perturbations are
then advected by the flow into complex shapes
Randomized Crossover Study Showing Nurse-Led Same Day Review Replacing Next Day Review in Uneventful Phacoemulsification to Be Safe and Efficacious
Purpose . To study whether nurse led same-day review (SDR) after uneventful phacoemulsification can replace next-day review (NDR) in terms of safety and efficacy. Setting . Patients are recruited from an ophthalmology outpatient clinic in Hong Kong. Design . A prospective, randomized crossover study conducted from November 2012 to 2014. Methods . Inclusion criteria include cataract surgery naïve patients undergoing phacoemulsification under local anaesthesia. All patients were seen by our ophthalmic nurse 2 hours after surgery. Before undergoing phacoemulsification of the first eye, patients were randomized to be reviewed on day 1 or 7 after surgery. Surgeons and reviewing doctors were blinded to patient allocation. For the patients’ second eye surgery, group allocation will cross over. Primary outcome measures include visual improvement and patient satisfaction questionnaire. Other measures include cataract characteristics, surgical details, and complications. Statistical tests include paired t -test, Wilcoxon signed rank test, and Chi-square test. Results . 164 eyes from 82 patients were available. Visual improvement, satisfaction, and complications were comparable between both groups. Conclusions . A nurse led SDR can replace NDR in uneventful phacoemulsification in terms of safety and efficacy. Patient satisfaction is also comparable in the setting of Asian culture and when transportation is not a major concern.published_or_final_versio
Nuclear and cell membrane surface area alteration in hexamethylene bisacetamide (HMBA) induced human colonic carcinoma cell line (LoVo)
Synopses of Paperspostprin
Walking in the cement forest: a health enhancement and pedometer-determined ambulatory (HEPA) program in Hong Kong
Congress Theme: A Celebration of Diversity and Inclusion in Active AgeingThis journal suppl.entitled: Supplement issue: Abstracts for the 8th World Congress on Ageing and Physical Activitypublished_or_final_versionThe 8th Annual World Congress on Active Ageing (WCAA): A Celebration of Diversity and Inclusion in Active Ageing, Glasgow, Scotland, UK, 13 -17 August 2012. In Journal of Aging and Physical Activity, 2012, v. 20, Suppl., p. S226-S22
Walking in the High-rise City: A Health Enhancement and Pedometer-determined Ambulatory (HEPA) Program in Hong Kong
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