Jet drops from bursting bubbles: How gravity and viscosity couple to inhibit droplet production

Background: COVID-19 has restricted singing in communal worship. We sought to understand variations in droplet transmission and the impact of wearing face masks. Methods: Using rapid laser planar imaging, we measured droplets while participants exhaled, said "hello" or "snake", sang a note or "Happy Birthday", with and without surgical face masks. We measured mean velocity magnitude (MVM), time averaged droplet number (TADN) and maximum droplet number (MDN). Multilevel regression models were used. Results: In 20 participants, sound intensity was 71 Decibels (dB) for speaking and 85 dB for singing (p<0.001). MVM was similar for all tasks with no clear hierarchy between vocal tasks or people and >85% reduction wearing face masks. Droplet transmission varied widely, particularly for singing. Masks decreased TADN by 99% (p<0.001) and MDN by 98% (p<0.001) for singing and 86-97% for other tasks. Masks reduced variance by up to 48%. When wearing a mask, neither singing task transmitted more droplets than exhaling. Conclusions: Wide variation exists for droplet production. This significantly reduced when wearing face masks. Singing during religious worship wearing a face mask appears as safe as exhaling or talking. This has implications for UK public health guidance during the COVID-19 pandemic.

Download Full-text

A novel microfluidic device for double emulsion formation: The effects of design parameters on droplet production performance

Colloids and Surfaces A Physicochemical and Engineering Aspects ◽

10.1016/j.colsurfa.2021.128059 ◽

2021 ◽

pp. 128059

Author(s):

Reza Yousofvand ◽

Kasra Ghasemi

Keyword(s):

Microfluidic Device ◽

Double Emulsion ◽

Production Performance ◽

Design Parameters ◽

Droplet Production

Download Full-text

Prediction of Droplet Production Speed by Measuring the Droplet Spacing Fluctuations in a Flow-Focusing Microdroplet Generator

Micromachines ◽

10.3390/mi10120812 ◽

2019 ◽

Vol 10 (12) ◽

pp. 812 ◽

Cited By ~ 1

Author(s):

Wen Zeng ◽

Dong Xiang ◽

Hai Fu

Keyword(s):

Fluid Flow ◽

Efficient Method ◽

Immiscible Fluids ◽

Droplet Generation ◽

Flow Focusing ◽

Flow Conditions ◽

Flow Rates ◽

Wide Range ◽

Droplet Production ◽

Monodisperse Droplets

In a flow-focusing microdroplet generator, by changing the flow rates of the two immiscible fluids, production speed can be increased from tens to thousands of droplets per second. However, because of the nonlinearity of the flow-focusing microdroplet generator, the production speed of droplets is difficult to quantitatively study for the typical flow-focusing geometry. In this paper, we demonstrate an efficient method that can precisely predict the droplet production speed for a wide range of fluid flow rates. While monodisperse droplets are formed in the flow-focusing microchannel, droplet spacing as a function of time was measured experimentally. We discovered that droplet spacing changes periodically with time during each process of droplet generation. By comparing the frequency of droplet spacing fluctuations with the droplet production speed, precise predictions of droplet production speed can be obtained for different flow conditions in the flow-focusing microdroplet generator.

Download Full-text

Faster droplet production by delayed surfactant-addition in two-phase microfluidics to form thermo-sensitive microgels

Journal of Colloid and Interface Science ◽

10.1016/j.jcis.2015.04.017 ◽

2015 ◽

Vol 452 ◽

pp. 38-42 ◽

Cited By ~ 7

Author(s):

Sebastian Seiffert ◽

Fabian Friess ◽

Andreas Lendlein ◽

Christian Wischke

Keyword(s):

Two Phase ◽

Droplet Production

Download Full-text

HG-100THE ROLE OF HYPOXIA ON LIPID DROPLET PRODUCTION IN GLIOBLASTOMA

Neuro-Oncology ◽

10.1093/neuonc/now073.96 ◽

2016 ◽

Vol 18 (suppl 3) ◽

pp. iii71.4-iii71

Author(s):

Robert Murren ◽

Daniel Tennant ◽

Andrew Peet

Keyword(s):

Lipid Droplet ◽

Droplet Production

Download Full-text

Development of a Simple Reversible-Flow Method for Preparation of Micron-Size Chitosan-Cu(II) Catalyst Particles and Their Testing of Activity

Molecules ◽

10.3390/molecules25081798 ◽

2020 ◽

Vol 25 (8) ◽

pp. 1798 ◽

Cited By ~ 2

Author(s):

Apichai Intanin ◽

Prawpan Inpota ◽

Threeraphat Chutimasakul ◽

Jonggol Tantirungrotechai ◽

Prapin Wilairat ◽

...

Keyword(s):

Alkaline Solution ◽

Catalytic Reduction ◽

Flow System ◽

Flow Line ◽

Switching Valve ◽

Micron Size ◽

Droplet Production ◽

The Mean ◽

Simple Flow ◽

Representative Samples

A simple flow system employing a reversible-flow syringe pump was employed to synthesize uniform micron-size particles of chitosan-Cu(II) (CS-Cu(II)) catalyst. A solution of chitosan and Cu(II) salt was drawn into a holding coil via a 3-way switching valve and then slowly pumped to drip into an alkaline solution to form of hydrogel droplets. The droplets were washed and dried to obtain the catalyst particles. Manual addition into the alkaline solution or employment of flow system with a vibrating rod, through which the end of the flow line is inserted, was investigated for comparison. A sampling method was selected to obtain representative samples of the population of the synthesized particles for size measurement using optical microscopy. The mean sizes of the particles were 880 ± 70 µm, 780 ± 20 µm, and 180 ± 30 µm for the manual and flow methods, without and with the vibrating rod, respectively. Performance of the flow methods, in terms of rate of droplet production and particle size distribution, are discussed. Samples of 180 µm size CS-Cu(II) particles were tested for catalytic reduction of 0.5 mM p-nitrophenol to p-aminophenol by 100-fold excess borohydride. The conversion was 98% after 20 min, whereas without the catalyst there was only 14% conversion.

Download Full-text

Technologies and Formulation Design of Polysaccharide-Based Hydrogels for Drug Delivery

Molecules ◽

10.3390/molecules25143156 ◽

2020 ◽

Vol 25 (14) ◽

pp. 3156 ◽

Cited By ~ 5

Author(s):

Giulia Auriemma ◽

Paola Russo ◽

Pasquale Del Gaudio ◽

Carlos A. García-González ◽

Mariana Landín ◽

...

Keyword(s):

Sol Gel ◽

Chemical Properties ◽

Drying Methods ◽

Special Focus ◽

Porous Network ◽

Hydrogel Particles ◽

Physico Chemical ◽

Droplet Production ◽

Inflammatory Drugs ◽

Sol Gel Transition

Polysaccharide-based hydrogel particles (PbHPs) are very promising carriers aiming to control and target the release of drugs with different physico-chemical properties. Such delivery systems can offer benefits through the proper encapsulation of many drugs (non-steroidal and steroidal anti-inflammatory drugs, antibiotics, etc) ensuring their proper release and targeting. This review discusses the different phases involved in the production of PbHPs in pharmaceutical technology, such as droplet formation (SOL phase), sol-gel transition of the droplets (GEL phase) and drying, as well as the different methods available for droplet production with a special focus on prilling technique. In addition, an overview of the various droplet gelation methods with particular emphasis on ionic cross-linking of several polysaccharides enabling the formation of particles with inner highly porous network or nanofibrillar structure is given. Moreover, a detailed survey of the different inner texture, in xerogels, cryogels or aerogels, each with specific arrangement and properties, which can be obtained with different drying methods, is presented. Various case studies are reported to highlight the most appropriate application of such systems in pharmaceutical field. We also describe the challenges to be faced for the breakthrough towards clinic studies and, finally, the market, focusing on the useful approach of safety-by-design (SbD).

Download Full-text