A groundbreaking discovery has revealed the water repellency mechanism in human eyes, with eyelashes playing a crucial role in keeping vision clear from liquid droplets. This remarkable feature is attributed to the unique shape and hydrophobic nature of eyelashes, which allows water to bead up and roll off effortlessly.
Eyelashes’ Special Features Help Fling Water from the Eyes
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The exterior of an eyelash acts like a “micro-ratchet,” allowing water to flow easily from root to tip but not in the opposite direction. This unique feature helps keep vision clear from liquid droplets.
How Eyelashes Keep Vision Clear
When loose eyelashes are dipped in water and pulled out again, more force is required to move the eyelash when the water is working against the ratchet than when going with it. Additionally, water beads up on the hairs and tends to roll off due to their hydrophobic nature.
The Science Behind Eyelashes’ Water-Wicking Ability
Experiments using arrays of nylon fibers with dimensions and elasticity similar to those of eyelashes have shown that the shape of a brachistochrone minimizes the time it takes for water droplets to slide off. The researchers found that droplets slid fastest off the brachistochrone, which is a curve that approximates the shape of an eyelash.
Implications and Limitations
This discovery has implications beyond just rainstorms. Eyelashes may also help in situations where water or liquid droplets are present, such as bathing, sweating, or crying. However, beauty treatments like mascara can alter the hydrophobic nature of eyelashes, making them more prone to attracting water.
References
S. Zhou et al. (2024). Rapid water drainage on human eyelashes of a hydrophobic Brachistochrone fiber array. Science Advances, 10(52), eadr2135. doi: 10.1126/sciadv.adr2135.
- sciencenews.org | Eyelashes’ special features help fling water from the eyes
