Through-hole composite membrane with an ultrathin oxide shell for highly robust and transparent air filters

Exploring pore structures that are optically transparent and have high filtration efficiency for ultrafine dust is very important for realizing passive window filters for indoor air purification. Herein, a polyester track-etched (PETE) membrane with vertically perforated micropores is investigated as a cost-effective candidate for trans-parent window filters. The pore size, which governs transparency and filtration efficiency, can be precisely tuned by conformally depositing an ultrathin oxide layer on the PETE membrane via atomic layer deposition. The maximum visible light transmittance (similar to 81.2 %) was achieved with an alumina layer of approximately 55 nm, and the resulting composite membrane exhibited competitive filtration efficiency compared to commercial products. The chemically inert alumina layer also increased resistance to various external stimuli and enabled simple cleaning of the contaminated membrane surface with a solvent. The membrane installed on an insect screen effectively maintained its filtration performance (similar to 85 % for PM2.5) even after 10 reuse cycles under extremely harsh conditions (PM2.5 concentration: similar to 5000 mu g cm-3). The proposed through-hole composite membrane can expand the choice of aesthetic window filters to situations that require high outside visibility and daylighting.

Automated summary

A polyester track-etched (PETE) membrane with vertically perforated micropores is studied as a cost-effective candidate for transparent window filters. The pore size can be adjusted by depositing an ultrathin oxide layer on the PETE membrane via atomic layer deposition. The resulting composite membrane exhibits competitive filtration efficiency and can be easily cleaned, making it suitable for aesthetically pleasing window filters.