Patent ID: 8523971

Claim:
A method of making a multilayer filter, comprising the steps of: (a) coating a layer of nanofibers on a single side or on both sides of a substrate layer to obtain a composite filter medium; and (b) folding the composite filter medium into a serpentine-shaped arrangement to form a multilayer filter wherein the composite filter medium is folded into a plurality of nanofiber layers arranged in a sequential arrangement having alternating essentially perpendicular segments and essentially parallel segments with respect to airflow; wherein the essentially perpendicular segments are larger than the essentially parallel segments; wherein when airflow is applied, air passes through the plurality of nanofiber layers; and wherein in the multilayer filter pressure drop is reduced by at least 20% when compared with a filter having nanofibers deposited in a single layer while attaining a filtration efficiency within 10% of the filter having the nanofibers deposited in a single layer.