查看更多>>摘要：We have developed a water harvesting condensation particle counter (WHCPC) using lab-onprinted circuit board (PCB) technology. Our method provides an inexpensive, compact, and highly accurate system for the ubiquitous monitoring of airborne ultrafine particles (UFPs). Labon-PCB-based WHCPC uses water as the working fluid to monitor harmless UFPs; it does not require water replenishment using a moderated water condensation method. Lab-on-PCB-based WHCPC consists of two main parts, a UFP growth section and a mini-OPC, through which UFPs are grown into micro-sized droplets and the grown droplets are single-counted. The UFP growth section consists of two PCBs and a 3D-printed channel. The heater, temperature sensor, and hydrophilic micropillar array wick, which are essential for the growth of UFPs, are integrated on the PCBs. Simulations were performed to verify the saturated-air generation and water collection in the UFP growth section. The dew points of the inlet and outlet air samples were measured to verify water collection using the moderated water condensation method. Through quantitative experiments using UFPs artificially generated in the laboratory, particles of 9.4 nm could be counted. It was possible to precisely measure the number concentration (2500-270000 N cm(-3)) over a wide range. In addition, the stability of the proposed system was confirmed through a long-term comparison with the reference CPC in an outdoor environment. The proposed system realized the sensorization of CPC because it could monitor harmless UFPs, with minimal maintenance; the proposed system is also inexpensive and compact.
查看更多>>摘要：The tension on the supply of surgical and FFP2 masks during the first wave of the COVID-19 pandemic leads to study the potential reuse of these masks. As washing is easily adaptable at home, this treatment solution was retained. In this work, thirty-six references of surgical masks and four FFP2 masks were tested without being worn or washed and after several washing cycles. The results highlighted a great heterogeneity of performances depending on the mask trademarks, both for surgical masks and FFP2. The quality of the meltblown and spunbond layers and the presence/absence of electrostatic charges at the fiber surface are put forward to explain the variability of results, both on differential pressures and filtration efficiencies. The differential pressure and the particle filtration efficiency of the washed masks were maintained up to 10 washing cycles and met the standard requirements. However, an immersion in water with a detergent induces an efficiency decrease for submicronic particles. This lower performance, constant after the first washing cycle, can be explained by the loss of electrostatic charges during the washing cycle. The modifications of surface properties after washing also lead to a loss of the hydrophobic behavior of type IIR surgical masks, which can therefore no more be considered as resistant to blood projections.
de la Mora, Juan FernandezKangasluoma, JuhaAttoui, Michel
6页
查看更多>>摘要：Brilke et al. (2020) have recently characterized several commercial condensation particle counters (CPCs) based on clusters of tetraheptylammonium bromide and tetrabutylammonium iodide. These seed particles were generated by a bipolar electrospray source (BES) and purified by high resolution mobility separation. Paradoxically, their results suggest that the size resolution achievable by scanning over CPC supersaturation is less than previously found with other aerosol sources, even though the BES tends to produce particles with singular shape and composition homogeneity. Here we report activation curves for the Airmodus A10 Particle Size Magnifier, tested with a diversity of mobility classified clusters, produced by a BES from the salts EMI-bis (trifluoromethylsulfonyl)imide and EMI-tris(pentafluoroethyl)trifluorophosphate (EMI = 1Ethyl-3-methylimidazolium). We find activation curves several times steeper than those of Brilke et al.
查看更多>>摘要：The collision between small adhesive particles and flat substrate is a fundamental phenomenon in both natural and industrial processes. Due to the complex coupling among the elastic deformation, surface adhesion and viscoelastic damping, a great gap still exists for directly obtaining a universal correlation for the restitution coefficient. In this work, we use the finite element method (FEM) to numerically investigate the wall collision of small adhesive particles. The surface adhesion is directly incorporated by the Hamaker theory and the viscoelastic dissipation is coupled to the local strain, stress and strain rate. The results show that the FEM model naturally captures the coupling between the surface adhesion and viscoelastic damping, and thus is capable to predict the proper restitution coefficient by directly using the surface energy of bulk materials, without any adjustment or fitting. By simulating a large number of wall collision cases in a wide range of impact parameters, we present new universal correlations for the restitution coefficient and critical sticking velocity, which agree well with the classic experimental data in a wide range of the incident velocity, particle size and particle/substrate material properties. Our explicit correlations can be easily incorporated into Eulerian-Lagrangian simulations for quantitatively describing the sticking/rebound behaviors of laden aerosol particles.
NSTL
Elsevier