Nonadhesion technology based on the lotus leaf. via asia.nikkei

What does the peel-off lid of a cup of yogurt have in common with a smartphone screen? They are both likely to benefit from next-generation nonadhesion technologies. These new ways of preventing things from sticking are also beneficial beyond the consumer sphere: Venice uses the new technologies to prevent flooding.

Toyo Aluminium wants you to wave goodbye to licking your yogurt lid.
Taking inspiration from nature, cutting-edge nonadhesion technologies may not lead to hit products, but it is likely to tweak designs on many everyday items.

Part of the yogurt eating ritual has always been licking the food off the foil lid. Over the course of a year, the yogurt stuck to lids worldwide is equivalent to the volume consumed in Africa, according to a calculation by Toyo Aluminium.

Morinaga Milk Industry is doing something about that: Its lids peel off clean with no stuck yogurt.

The company uses a special lid developed in cooperation with Toyo Aluminium. It is based on a packaging technology Toyo calls “Toyal Lotus.” The material’s structural inspiration was the lotus leaf, which is famous for its ability to shed water and remain dry.

Fresh angles

How does the lotus leaf do this? Its structure pushes liquids up into droplets because of its very high contact angle.

Imagine a water droplet on a table, and consider the angle between the outer edge of this drop and the surface of the table. If the contact angle is smaller than 90 degrees, water has a tendency to spread out and wet the surface. On the other hand, a higher contact angle means the surface is more water-repellent, and will turn the liquid into droplets.

The Morinaga yogurt lid stays clean because its design, like that of a lotus leaf, creates a large contact angle for liquids. “The contact angle for a water droplet on a lotus leaf is 150 degrees,” said Toyo executive Masashi Yamamoto. “To repel water, a similarly large contact angle is needed.” The company has made the angle larger, at 170 degrees.

A water-repellant material, in addition, coats the yogurt lid, which is also processed to have microscopic protrusions similar to those on lotus leaves. These protrusions provide pockets for air that work to push back up against any liquid droplets that could fill the protrusions. Toyal Lotus is designed to keep in large layers of air.

Other yogurt makers have begun using Toyo’s technology.

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