Abstract
•Isoporous structure has the potential to achieve high filtration efficiency as the pore sizes can be designed to achieve accurate size selectivity.•we report an approach to simultaneously maximize filtration efficiency and minimize pressure drop in multi-layer isoporous membranes via a built-in micro-spacer array.•Finite element analysis (FEA) reveals the effects of the micro-spacer geometries in controlling the air stream direction, the associated kinetic loss and hence the reduced pressure drop across bilayer isoporous membranes.•The FEA results corroborate the performance of experimentally fabricated bilayer isoporous membranes with built-in micro-spacer array; a low pressure drop of ∼300 Pa at 7 cm/s, and >95% filtration efficiency for particle between 300 nm and 2 µm has been achieved.•The introduction of micro-spacer array in multi-layer isoporous membranes extends the performance limit of traditional filtration media especially for challenging applications such as air purification and respiratory filtration under high workload conditions.
Isoporous membranes with well-defined pore architectures offer a unique design approach to achieve a multi-scale porous network. For instance, isoporous membranes with progressively smaller pore sizes can be stacked to create a hierarchical pore network in which each length scale and the gradient of the pore network are deterministic by design. In this paper, we introduce a hierarchically-arranged multilayer isoporous air filter that comprises an ultrathin (thickness <1μm) nanoporous active filtration layer and a microporous support layer. To maximize airflow and thereby reduce pressure drop across the membrane, we engineered a gap between the nanoporous and microporous membranes by designing and fabricating microscale spacer structures akin to feed spacers used in spiral wound reverse osmosis membranes. We demonstrated that such hierarchical isoporous membranes with integrated spacers (HIM-S) can retain high filtration efficiency (>95%) for ultrafine, most penetrating particle size (MPPS) while simultaneously reducing the pressure drop across the membrane (by ∼86%).
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