Characterization of mass distribution in a biomimetic aerosol exposure system

OBJECTIVE

Lack of biomimicry in geometry and flow conditions of emissions systems for analytical testing and biological exposure has led to fundamental limitations, including a poor understanding of dose delivered to specific airway locations. This work characterizes mass distribution of a JUUL® brand e-cigarette in a Biomimetic Aerosol Exposure System (BAES).

MATERIALS AND METHODS

A combination of mass balance, direct measurements, and inferences based on direct measurements were used to characterize regional and local dose as a function of system flow path configuration and emissions topography profile.

RESULTS

Doses produced by the emissions topography profile with only puffing were significantly different from profiles with clean air inhalation following puffs. Mass characterization results support that dose can be manipulated using flow path geometry. Local and regional deposition was mapped throughout the system.

DISCUSSION AND CONCLUSIONS

We estimate the fraction of yield to the mouth deposited at several locations throughout the system for a variety of puffing and respiration topographies and show that emissions topography profile and system flow path geometry affect dose. This work provides proof-of-concept for assessing mass distribution as a function of aerosol generator (e-cigarette product), user airway geometry, and inhalation and puffing topography.

Rapid Direct Detection of SARS-CoV-2 Aerosols in Exhaled Breath at the Point of Care

Airborne transmission via virus-laden aerosols is a dominant route for the transmission of respiratory diseases, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Direct, non-invasive screening of respiratory virus aerosols in patients has been a long-standing technical challenge. Here, we introduce a point-of-care testing platform that directly detects SARS-CoV-2 aerosols in as little as two exhaled breaths of patients and provides results in under 60 s. It integrates a hand-held breath aerosol collector and a llama-derived, SARS-CoV-2 spike-protein specific nanobody bound to an ultrasensitive micro-immunoelectrode biosensor, which detects the oxidation of tyrosine amino acids present in SARS-CoV-2 viral particles. Laboratory and clinical trial results were within 20% of those obtained using standard testing methods. Importantly, the electrochemical biosensor directly detects the virus itself, as opposed to a surrogate or signature of the virus, and is sensitive to as little as 10 viral particles in a sample. Our platform holds the potential to be adapted for multiplexed detection of different respiratory viruses. It provides a rapid and non-invasive alternative to conventional viral diagnostics.

Sintering Rate and Mechanism of TiO2 Nanoparticles by Molecular Dynamics

Titania is the dominant white pigment and photocatalytic material, a key component of sunscreens and has promising applications in photovoltaics and sensors of organic vapors. The growth of TiO₂ nanoparticles by sintering, the critical step during their large scale manufacture and processing, is elucidated and quantified by molecular dynamics. Highly mobile ions from the particle surface fill in the initially concave space between nanoparticles (surface diffusion) forming the final, fully-coalesced, spherical-like particle with minimal displacement of inner Ti and O ions (grain boundary diffusion) revealing also the significance and sequence of these two sintering mechanisms of TiO₂. A sintering rate for TiO₂ nanoparticles is extracted that is much faster than that in the literature but nicely converges to it for increasing particle size.