Researchers are looking at a mixture of bee spit and flower oil to create a bio-inspired glue.
Why? Its unique adhesive properties and ability to remain sticky through a range of conditions.
Honey bees spend hours each day collecting pollen and packing it into tidy bundles attached to their hind legs. But all of that hard work could instantly be undone during a sudden rainstorm were it not for two substances the insect uses to keep the pollen firmly stuck in place: bee spit and flower oil.
“A bee encounters not just wet and humid environments but windy and dry surroundings as well, so its pollen pellet must counteract those variations in humidity while remaining adhered,” says J. Carson Meredith, a professor in Georgia Tech’s School of Chemical and Biomolecular Engineering. “Being able to withstand those kinds of changes in humidity is still a challenge for synthetic adhesives.”
In a study in Nature Communications, the researchers described how those two natural liquids work together to protect the bee’s bounty as it travels back to its hive.
Better together
The first component of the glue is the bee’s own salivary secretions, which coat the pollen grains and allow them to stick together. The bees produce those sugary secretions, the main ingredient in honey, from nectar they drink from the flowers.
The second ingredient is a plant-based oil that coats the pollen grains called pollenkitt, which helps stabilize the adhesive properties of the nectar and protect it from the impact of too much or too little humidity.
“It works similarly to a layer of cooking oil covering a pool of syrup,” Meredith says. “The oil separates the syrup from the air and slows down drying considerably.”
The researchers tested the adhesive properties of the bee’s glue by separating the oil-based component from the sugar-based component and evaluating how sticky the nectar remained under various humidity conditions.
As expected, as humidity increased and the nectar absorbed more water, its adhesive properties diminished. The same effect was true when humidity decreased and the nectar dried out. Meanwhile, under similar conditions, nectar coated with the pollenkitt oil remained sticky despite changes in humidity.
Perfect for sticky situations
“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,” Meredith says. “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 team also examined dynamics of the bee adhesive.
“We wanted to know, if the pollen can stay so firmly attached to the bee’s hind legs, how do the bees manage to remove it when they return to the hive,” Meredith says.
The answer may lie in the adhesive’s a rate-sensitive response. In other words, the faster the force attempting to remove it, the more it would resist.
“This is a property of capillary adhesion, which we believe could be harnessed and tailored for specific applications, such as controlling motion in microscopic or nanoscale devices, in fields ranging from construction to medicine,” Meredith says.
The Air Force Office of Scientific Research supported the research. Any conclusions or recommendations are those of the authors and do not necessarily represent the official views of the sponsoring organizations.
Source: Georgia Tech
