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Today's options for portable water filtration of tiny particles mostly consist of filter paper and microporous membranes.

Blood obtained by pricking a baby’s heel was collected on filter paper and tested for phenylketonuria, a rare metabolic condition that, if untreated, causes intellectual disability.

For instance, Russia produces a lot of tea, Mr. Fedyakov said, but it imports the filter paper used in tea bags.

This involves placing a piece of filter paper for 60 seconds between a dog’s lower eyelid and cornea.

The scientists wiped the armpits of healthy people and dengue fever patients with an absorbent material, isolated the molecules that could become airborne, and dabbed them onto filter paper.