Small-Angle Particle Counting Coupled Photometry for Real-Time Detection of Respirable Particle Size Segmentation Mass Concentration

Respirable particulate matter air pollution is positively associated with SARS-CoV-2 mortality. Real-time and accurate monitoring of particle concentration changes is the first step to prevent and control air pollution from inhalable particles. In this research, a new light scattering instrument has been developed to detect the mass concentration of inhalable particles. This instrument couples the forward small-angle single particle counting method with the lateral group particle photometry method in a single device. The mass concentration of four sizes of inhalable particles in the environment can be detected simultaneously in a large area in real-time without using a particle impactor. Different from the traditional light scattering instrument, this new optical instrument can detect darker particles with strong light absorption, and the measurement results mainly depend on the particle size and ignore the properties of the particles. Comparative experiments have shown that the instrument can detect particles with different properties by simply calibrating the environmental density parameters, and the measurement results have good stability and accuracy.

Aerosol Generation in Ear Canal and Air-Fluid Interface Suction

Objective The identification of aerosol-generating procedures (AGPs) is important during the current SARS-CoV-2 pandemic due to aerosol-mediated virus transmission. Aerosol measurement during clinical procedures using particle counting may be confounded by variable natural background aerosol levels or limited by partial volume sampling. The study objective was to quantify any significant aerosol generated from simulated suction clearance procedures. Study Design Prospective quantification of aerosol generation during clinical suction simulation. Setting Clean chamber. Methods We created a clean environment for particle counting in a transparent neutralized polypropylene chamber. Air was passed through a HEPA 14 class filter to maintain a constant chamber inlet pressure. An optical particle counter was connected in line to the chamber exhaust vent to measure all of the vented particles. The chamber background count was 1 particle ≥0.3 µm per 15 minutes at a flow rate of 1 chamber air change per minute. We used this system to quantify very low aerosol counts generated from suction clearance of a silicone ear canal and at an open air-fluid interface. Results No clinically significant aerosol generation was found by particle counting of the whole chamber air volume during simulated suction procedures. Conclusion Simulated ear suction clearance and air-fluid interface suction does not generate any significant aerosol. It appears likely that any aerosol potentially generated at the suction tube tip is entrained by incoming air flow. This is the first study to quantify aerosols generated by suction in a controlled environment; further research is required to determine its clinical implications.

Homogeneous Digital Biosensor for Circulating Tumor DNA by Enumerating Dual-color Quantum Dot Complex

Monitoring ctDNA in blood is important to cancer management. Here, we develop a one-step single particle counting approach for directly quantifying ctDNA in plasma. Hairpin DNA containing a triple helix...

Simultaneous and continuous particle separation and counting via localized DC-dielectrophoresis in a microfluidic chip

The first report that particle counting and separation can be achieved simultaneously. Separation and counting of polystyrene particles of two and three different sizes with 1 μm resolution were demonstrated experimentally.