Interfacial Stresses within Droplets and Channels Influence Bacterial Physiology: A Perspective.

Bacterial cells frequently experience fluid motion in their natural environments, like water bodies, aerosols, fomites, human capillaries, etc., a phenomenon that researchers have largely overlooked. Nevertheless, some reports have suggested that the interfacial stresses caused by fluid motion inside evaporating droplets or shear flows within capillaries may trigger physiological and morphological changes in the bacterial cells.

Weather-related changes in the dehydration of respiratory droplets on surfaces bolster bacterial endurance.

Hypothesis: The study shows for the first time a fivefold difference in the survivability of the bacterium Pseudomonas Aeruginosa (PA) in a realistic respiratory fluid droplet on fomites undergoing drying at different environmental conditions. For instance, in 2023, the annual average outdoor relative humidity (RH) and temperature in London (UK) is 71 % and 11 °C, whereas in New Delhi (India), it is 45 % and 26 °C, showing that disease spread from fomites could have a demographic dependence. Respiratory fluid droplet ejections containing pathogens on inanimate surfaces are crucial in disease spread, especially in nosocomial settings.

Future research perspective on the interfacial physics of non-invasive glaucoma testing in pathogen transmission from the eyes.

Non-contact tonometry (NCT) is a non-invasive ophthalmologic technique to measure intraocular pressure (IOP) using an air puff for routine glaucoma testing. Although IOP measurement using NCT has been perfected over many years, various phenomenological aspects of interfacial physics, fluid structure interaction, waves on corneal surface, and pathogen transmission routes to name a few are inherently unexplored. Research investigating the interdisciplinary physics of the ocular biointerface and of the NCT procedure is sparse and hence remains to be explored in sufficient depth.

Observations on phenomenological changes in under fluidic stresses.

In the present work, experiments are conducted to understand the consequence of stresses generated by flowing fluid on the bacterial morphology and virulence in microfluidic channels. We consider (KP, a clinical isolate), an ESKAPE pathogen, to be the model bacteria responsible for blood stream infections, bacteremia, including pneumonia, urinary tract infections and more. Four different stress conditions are generated by changing the flow rate and channel geometry subsequently altering the shear rate and stressing time ().

maintains the environmental persistence and virulence of pathogenic bacteria in mechanically stressed desiccated droplets.

Despite extensive studies on kinematic features of impacting drops, the effect of mechanical stress on desiccated bacteria-laden droplets remains unexplored. In the present study, we unveiled the consequences of the impaction of bacteria-laden droplets on solid surfaces and their subsequent desiccation on the virulence of an enteropathogen typhimurium (STM). The methodology elucidated the deformation, cell-cell interactions, adhesion energy, and roughness in bacteria induced by impact velocity and low moisture because of evaporation.

On the specific heat capacity of HITEC-salt nanocomposites for concentrated solar power applications.

High specific heat capacity or of molten salt is crucial for concentrated solar power plants as it will enhance the energy density of thermal energy storage. It can be achieved by doping nanoparticles into molten salts. However, reported results show inconsistency in enhancement (positive and negative).

Physics of self-assembly and morpho-topological changes of Klebsiella pneumoniae in desiccating sessile droplets.

Hypothesis: The bacteria suspended in pure water self-assemble into unique patterns depending on bacteria-bacteria, bacteria-substrate and bacteria-liquid interactions. The physical forces acting on bacteria vary based on their respective spatial location inside the droplet cause an assorted magnitude of physical stress. The shear and dehydration induced stress on pathogens(bacteria) in drying bio-fluid droplets alters the viability and infectivity.

Evaporation dynamics of a surrogate respiratory droplet in a vortical environment.

Hypothesis: Vortex droplet interaction is crucial for understanding the route of disease transmission through expiratory jet where several such embedded droplets continuously interact with vortical structures of different strengths and sizes.

Experiments: A train of vortex rings with different vortex strength, quantified with vortex Reynolds number (Re=0,53,221,297) are made to interact with an isolated levitated droplet, and the evolution dynamics is captured using shadowgraphy, particle image velocimetry (PIV), and backlight imaging technique. NaCl-DI water solution of 0, 1, 10 and 20 wt% concentrations are used as test fluids for the droplet.

Malleable Patterns from the Evaporation of a Colloidal Liquid Bridge: Coffee Ring to the Scallop Shell.

The present article highlights an approach to generating contrasting patterns from drying colloidal droplets in a liquid bridge configuration, different from well-known coffee rings. Reduction of the confinement distance (the gap between the solid surfaces) leads to systematized nanoparticle agglomeration yielding spoke-like patterns similar to those found on scallop shells instead of circumferential edge deposition. Alteration of the confinement distance modulates the curvature that entails variations in the evaporation flux across the liquid-vapor interface.

Multiscale vapor-mediateddendritic pattern formation and bacterial aggregation in complex respiratory biofluid droplets.

Hypothesis: Deposits of biofluid droplets on surfaces (such as respiratory droplets formed during an expiratory) are composed of water-based salt-protein solution that may also contain an infection (bacterial/viral). The final patterns of the deposit formed and bacterial aggregation on the deposits are dictated by the fluid composition and flow dynamics within the droplet.

Experiments: This work reports the spatio-temporal, topological regulation of deposits of respiratory fluid droplets and control of bacterial aggregation by tweaking flow inside droplets using non-contact vapor-mediated interactions.

Two-dimensional mathematical framework for evaporation dynamics of respiratory droplets.

In majority of pandemics in human history, respiratory bio-aerosol is the most common route of transmission of diseases. These tiny droplets ejected through mouth and nose from an infected person during exhalation process like coughing, sneezing, speaking, and breathing consist of pathogens and a complex mixture of volatile and nonvolatile substances. A cloud of droplets ejected in such an event gets transmitted in the air, causing a series of coupled thermo-physical processes.

Risk Assessment of Aerosol Generation During Vitreoretinal Surgery Using High Speed Imaging Amidst the COVID-19 Pandemic.

Purpose: The purpose of this study was to discuss the propensity of aerosol and droplet generation during vitreoretinal surgery using high speed imaging amidst the coronavirus disease 2019 (COVID-19) pandemic.

Methods: In an experimental set up, various steps of vitreoretinal surgery were performed on enucleated goat eyes. The main outcome measures were visualization, quantification of size, and calculation of aerosol spread.

Spatiotemporal evaporating droplet dynamics on fomites enhances long term bacterial pathogenesis.

Naturally drying bacterial droplets on inanimate surfaces representing fomites are the most consequential mode for transmitting infection through oro-fecal route. We provide a multiscale holistic approach to understand flow dynamics induced bacterial pattern formation on fomites leading to pathogenesis. The most virulent gut pathogen, Salmonella Typhimurium (STM), typically found in contaminated food and water, is used as model system in the current study.

Efficacy of homemade face masks against human coughs: Insights on penetration, atomization, and aerosolization of cough droplets.

Ever since the emergence of the ongoing COVID-19 pandemic, the usage of makeshift facemasks is generally advised by policymakers as a possible substitute for commercially available surgical or N95 face masks. Although such endorsements could be economical and easily accessible in various low per-capita countries, the experimental evidence on the effectiveness of such recommendations is still lacking. In this regard, we carried out a detailed experimental investigation to study the fate of a large-sized surrogate cough droplet impingement at different velocities (corresponding to mild to severe coughs) on various locally procured cloth fabrics.

Fluid dynamics of droplet generation from corneal tear film during non-contact tonometry in the context of pathogen transmission.

Noninvasive ocular diagnostics demonstrate a propensity for droplet generation and present a potential pathway of distribution for pathogens such as the severe acute respiratory syndrome coronavirus 2. High-speed images of the eye subjected to air puff tonometry (glaucoma detection) reveal three-dimensional, spatiotemporal interaction between the puff and tear film. The interaction finally leads to the rupture and breakup of the tear film culminating into sub-millimeter sized droplet projectiles traveling at speeds of 0.

Precipitation dynamics of surrogate respiratory sessile droplets leading to possible fomites.

Hypothesis: The droplets ejected from an infected host during expiratory events can get deposited as fomites on everyday use surfaces. Recognizing that these fomites can be a secondary route for disease transmission, exploring the deposition pattern of such sessile respiratory droplets on daily-use substrates thus becomes crucial.

Experiments: The used surrogate respiratory fluid is composed of a water-based salt-protein solution, and its precipitation dynamics is studied on four different substrates (glass, ceramic, steel, and PET).

An opinion on the multiscale nature of Covid-19 type disease spread.

Recognizing the multiscale, interdisciplinary nature of the Covid-19 transmission dynamics, we discuss some recent developments concerning an attempt to construct a disease spread model from the flow physics of infectious droplets and aerosols and the frequency of contact between susceptible individuals with the infectious aerosol cloud. Such an approach begins with the exhalation event-specific, respiratory droplet size distribution (both airborne/aerosolized and ballistic droplets), followed by tracking its evolution in the exhaled air to estimate the probability of infection and the rate constants of the disease spread model. The basic formulations and structure of submodels, experiments involved to validate those submodels, are discussed.

Spatio-temporal modulation of self-assembled central aggregates of buoyant colloids in sessile droplets using vapor mediated interactions.

A functional sessile droplet containing buoyant colloids (ubiquitous in applications like chemical sensors, drug delivery systems, and nanoreactors) forms self-assembled aggregates. The particles initially dispersed over the entire drop-flocculates at the center. We attribute the formation of such aggregates to the finite radius of curvature of the drop and the buoyant nature of particles.

Insights on drying and precipitation dynamics of respiratory droplets from the perspective of COVID-19.

We isolate a nano-colloidal droplet of surrogate mucosalivary fluid to gain fundamental insights into airborne nuclei's infectivity and viral load distribution during the COVID-19 pandemic. The salt-water solution containing particles at reported viral loads is acoustically trapped in a contactless environment to emulate the drying, flow, and precipitation dynamics of real airborne droplets. Similar experiments validate observations with the surrogate fluid with samples of human saliva samples from a healthy subject.

On secondary atomization and blockage of surrogate cough droplets in single- and multilayer face masks.

Face masks prevent transmission of infectious respiratory diseases by blocking large droplets and aerosols during exhalation or inhalation. While three-layer masks are generally advised, many commonly available or makeshift masks contain single or double layers. Using carefully designed experiments involving high-speed imaging along with physics-based analysis, we show that high-momentum, large-sized (>250 micrometer) surrogate cough droplets can penetrate single- or double-layer mask material to a significant extent.

Dissolution dynamics of a vertically confined sessile droplet.

We experimentally investigate the dissolution of microscale sessile alcohol droplets in water under the influence of impermeable vertical confinement. The introduction of confinement suppresses the mass transport from the droplet to bulk medium in comparison with the nonconfined counterpart. Along with a buoyant plume, flow visualization reveals that the dissolution of a confined droplet is hindered by a mechanism called levitated toroidal vortex.

Propensity of aerosol and droplet creation during oculoplastic procedures: A risk assessment with high-speed imaging amidst COVID-19 pandemic.

Purpose: The study uses principles of liquid and gas mechanics to verify and quantify the generation of aerosols in oculoplastic procedures, namely surgery using a scalpel, electrosurgical device, and a mechanized drill.

Methods: Surgical techniques were performed ex vivo using the electrosurgical device, scalpel, and mechanized drill on the muscle and bone of commercially available chicken. The liquid and gas dynamics were observed using a high-speed high-resolution Photron SA5 camera (0.

Evaporation-induced alterations in oscillation and flow characteristics of a sessile droplet on a rose-mimetic surface.

Strategic control of evaporation dynamics can help control oscillation modes and internal flow field in an oscillating sessile droplet. This article presents the study of an oscillating droplet on a bio-inspired "sticky" surface to better understand the nexus between the modes of evaporation and oscillation. Oscillation in droplets can be characterized by the number of nodes forming on the surface and is referred to as the mode of oscillation.

Analyzing the dominant SARS-CoV-2 transmission routes toward an disease spread model.

Identifying the relative importance of the different transmission routes of the SARS-CoV-2 virus is an urgent research priority. To that end, the different transmission routes and their role in determining the evolution of the Covid-19 pandemic are analyzed in this work. The probability of infection caused by inhaling virus-laden droplets (initial ejection diameters between 0.