Materials

Bee-slobber-inspired adhesive may succeed where others fail

A honeybee, with a pollen pellet stuck to one of its hind legs
A honeybee, with a pollen pellet stuck to one of its hind legs
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A honeybee, with a pollen pellet stuck to one of its hind legs
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A honeybee, with a pollen pellet stuck to one of its hind legs

Depending on their formulation, most adhesives fail either when they're exposed to excessive humidity, or when they dry out in arid conditions. Honeybees, however, don't have such problems with their "pollen pellets." A new understanding of why this is so could lead to better manmade adhesives.

In a study conducted at Georgia Tech, scientists analyzed the "glue" that the bees use to adhere bundles of collected pollen onto their hind legs. It had already been noted that these pellets stayed put both in humid/rainy and windy/dry conditions. Such versatility is difficult to match using synthetic adhesives.

It was found that the glue consists of bee saliva that is rich in sugar derived from flower nectar, along with a plant-based oil known as pollenkitt. While the sugary saliva keeps the pollen grains stuck to one another, the oil forms a thin coating that keeps existing moisture from evaporating out, while also keeping external moisture from getting in.

To confirm this finding, the researchers removed the oil from the saliva, then tested the stickiness of the saliva in the lab. As expected, the absence of the oil caused the saliva to fail as an adhesive under both wet and dry conditions – this wasn't the case with a control sample of the saliva/oil combo, that was tested in similar settings.

"We believe you could take the essential concepts of this material and develop a novel adhesive with a water-barrier external oil layer that could better resist humidity changes in the same way," says Prof. J. Carson Meredith. "Or potentially this concept would apply to controlling the working time of an adhesive, such as its ability to flow and time to dry or cure."

The research is described in a paper that was recently published in the journal Nature Communications.

Source: Georgia Tech

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