ABSTRACT
Respiratory parameters, such as respiratory rate (RR), inhalation time (tin), exhalation time (tex), and their ratio (IER=tin/tex), are of great importance to indicate clinical differences between healthy people and those with respiratory diseases. Herein, we report a respiration monitoring triboelectric nanogenerator (RM-TENG) with nanofibrous membranes, which can be used as a smart, changeable, self-powered mask filter with high filtration efficiency for monitoring multiple respiratory indices (e.g., RR, tin, tex, IER). We created a mathematical model to quantitatively analyze the effects of gap distance between two triboelectric layers on the contact area by recording the nanofibers layer's deformation profile with digital image correlation (DIC) tests. The RM-TENG is more sensitive to smaller gap distances between 1mm - 5mm because the high specific area of nanofibers can provide a more effective contact area. An RM-TENG built with optimized structure parameters can accurately and consistently detect the above-mentioned respiratory indices with excellent sensing stability for 40hours. The monitored RR and IER have 100% and 93.53% agreement with the real-time RR and IER set on the ventilator, respectively. Furthermore, it has a filtration efficiency of 99wt% for particle sizes between 0.3µm and 5µm. This study introduces a mask filter fabricated with a simple structure with both filtering and sensing capability, which has excellent potential for self-powered health diagnostics.
ABSTRACT
Protective masks ? worn properly - have become the key to wither away the COVID-19 pandemic. Nowadays, the vast majority of these masks are made of nonwoven fabrics. High-quality products have mainly melt-blown filtering layers of nano/microfiber. Melt blowing produces very fine synthetic nonwovens from a wide range of polymers and allows a fair control of the fiber structure and morphology that makes it ideal for filtration purposes. Melt blowing has a high throughput, and the low price of the filter makes these products widely available for civil use. Although melt-blown fiber applications were rapidly growing in the last three decades, we still have limited knowledge on the processing parameters. In this regard, we detailed the melt blowing parameters to obtain a filter media with high particle capturing efficiency and a low-pressure drop. We summarized the melt-blown fiber mat characteristics with specific attention to the pore size, the porosity, the fiber diameter, the fiber packing density and the air permeability desired for highly efficient filtration. Even though we cannot estimate the future social effects and the trauma caused by the current pandemic, and protective masks might remain a part of everyday life for a long while. That also implies that near-future investments in wider manufacturing capacities seem inevitable. This paper also aims to facilitate masks' production with improved filtration efficiency by reviewing the recent developments in melt blowing, the related applications, the effects of processing parameters on the structure and performance of the nonwoven products focusing on the filtration efficiency via knowledge.
ABSTRACT
Face masks are becoming one of the most useful personal protective equipment with the outbreak of the coronavirus (CoV) pandemic. The entire world is experiencing shortage of disposable masks and melt-blown non-woven fabrics, which is the raw material of the mask filter. Recyclability of the discarded mask is also becoming a big challenge for the environment. Here, we introduce a facile method based on electrospinning and three-dimensional printing to make changeable and biodegradable mask filters. We printed polylactic acid (PLA) polymer struts on a PLA nanofiber web to fabricate a nanoporous filter with a hierarchical structure and transparent look. The transparent look overcomes the threatening appearance of the masks that can be a feasible way of reducing the social trauma caused by the current CoV disease-19 pandemic. In this study, we investigated the effects of nozzle temperature on the optical, mechanical, and morphological and filtration properties of the nanoporous filter.