A method of making a corrugated nonwoven web of polymeric microfiber, which method comprises:(a) introducing a nonwoven web of polymeric microfiber having a solidity of 0.1 or less into a corrugating apparatus that has a plurality of paddles secured at a first end to a means for moving the paddles about a path, the nonwoven web of polymeric microfiber making contact with spaced second ends of the paddles opposite to the paddles' first ends; and(b) reducing the spacing between the second ends of the paddles to cause the nonwoven web of polymeric microfiber to become corrugated, wherein the corrugated nonwoven web of polymeric microfiber has a solidity of 0.1 or less.