Dynamic multifunctional all-chalcogenide metasurface filter with ultra-multiple cycles

Dynamically tunable metasurfaces employing chalcogenide phase-change materials(PCMs)such as Ge_(2)Sb_(2)Te_(5)alloys have garnered significant attention and research efforts.However,the utilization of chalcogenide PCMs in dynamic metasurface devices necessitates protection,owing to their susceptibility to volatilization and oxidation.Conventional protective layer materials such as Al_(2)O_(3),TiO_(2),and SiO_(2)present potential drawbacks including diffusion,oxidation,or thermal expansion coefficient mismatch with chalcogenide PCMs during high-temperature phase transition,severely limiting the durability of chalcogenide PCM-based devices.In this paper,we propose,for the first time to our knowledge,the utilization of chalcogenide glass characterized by high thermal stability as a protective material for chalcogenide PCM.This approach addresses the durability challenge of current dynamic photonic devices based on chalcogenide PCM by virtue of their closely matched optical and thermal properties.Building upon this innovation,we introduce an all-chalcogenide dynamic tunable metasurface filter and comprehensively simulate and analyze its characteristics.This pioneering work paves the way for the design and practical implementation of optically dynamically tunable metasurface devices leveraging chalcogenide PCMs,ushering in new opportunities in the field.

Assessment of the risk of infectious aerosols leaking to the environment from BSL-3 laboratory HEPA air filtration systems using model bacterial aerosols

To assess the risk of infectious bacterial aerosols leaking to the environment, the filtration efficiency of a biosafety level 3 （BSL-3） laboratory high-efficiency particulate （HEPA） filter was investigated using the aerosolized bacteria Serratia marcescens. The aerosol size was measured using an Andersen sampler. Eight first stage HEPA filters （numbered 1-87 were distributed in contaminated labs and exhausts from each of the first stage HEPA filters were aggregated and filtered through one second stage HEPA filter before being released to the environment. In total, 8 first-stage and I second-stage HEPA filters from the BSL-3 air purification system were analyzed. No S. marcescens was detected in first stage filters 1,2, 4, 5, 7 and 8 and the second stage HEPA filter. The filtration efficiencies against aerosolized S. marcescens were 〉99.9999%. First stage filter numbers 3 and 6 had filtration efficiencies of 99.9825% and 99.9906% respectively. When filter number 3 was replaced by a new filter and the bracket for filter number 6 was sealed, no aerosolized S. marcescens was detected in the filtered air. Our work suggests that the BSL-3 laboratory HEPA filter air purification system is effective against bacterial aerosols, with little to no bacterial leakage into the environment.