Gradient transparency of Semi-IPN PVA/PVME electrospun nanofibrous membrane for estimating the remaining life of face mask

After suffering the COVID-19 viruliferous epidemic outbreak, wearing disposable protective masks has become an effective protective measure in our daily life. However, protection effectiveness of disposable protective masks will be greatly reduced or even lost once overstep their service life span. Thus, developing a strategy that can identify the remaining service life of masks by naked eyes becomes desirable. Here, we prepared a gradient transparent membrane as a view layer of masks by electrospinning the semi-interpenetration PVA/PVME membrane (semi-IPNM) which rapid responded to the respiration moisture. Based on the Darcy law by COMSOL software, with the increasing time of respiration simulation, the transparent area diffused from center to the edge of the membrane, like a progress bar revealing the remaining life of face mask. The resultant semi-IPNM exhibited excellent flexibility, nontoxicity, high tensile strength (34.5 MPa) and reliable filtration efficiency (greater than92%) even through 6 h using. Meanwhile, the pressure drop of semi-IPNM became higher after 6 h using, which was not meet up with human needs that indicated the disposable face mask should be discarded according to WS/T 311–2009 technical specification. Therefore, a view layer of face masks built by this strategy possesses a real-time service life management and an effective respiratory protection.