Next time you’re caught in the rain, thank your eyelashes for keeping your vision clear. Several traits help eyelashes fling water away from the eyes, a new study finds.
One secret to their water-wicking superpower is their structure. The outside of an eyelash, or cuticle, is covered in scales. These scales overlap like shingles on a roof. That structure acts like a “micro-ratchet,” researchers in China now find. Water can flow easily from root to tip, but not the other way round.
In one experiment, scientists dipped loose eyelashes in water and pulled them out again. More force was required to move the eyelash when the water was working against the ratchet than when going with it.
In another test, researchers dripped water on loose eyelashes. This showed that eyelashes are hydrophobic. That is, water beads up on them and tends to roll off.
A team at the Chinese Academy of Sciences in Beijing did the research. It shared the new findings December 20 in Science Advances.
Eyelashes also are shaped like a brachistochrone (Bra-KIS-toh-kroan). This type of curve minimizes the time it takes to get from point A to B under the force of gravity.
To test how this might affect the ability of eyelashes to remove water, the scientists worked with nylon fibers. These had a size and stretchiness similar to eyelashes.
They compared fibers in the shape of a brachistochrone to those that were were straight or curved in some other shape. The droplets slid fastest off the brachistochrone.
Eyelashes were already known to guard against dust. But they hadn’t been known for their water-flicking traits. This newfound effect could help keep vision clear when out in the rain, bathing, sweating or crying.
Beauty treatments could mess with this ability, though. Mascara can make eyelashes attract water instead of repelling it. And curling lashes alters their shape.
