Researchers at Georgia Institute of Technology are looking at a bee spit and flower oil mixture of ingredients as a model for a bioinspired glue because of its unique adhesive properties and ability to remain sticky through a range of conditions.
Bees don’t just transport pollen between plants, they also bring balls of it back to the hive for food. These “pollen pellets,” which also include nectar and can account for 30% of a bee’s weight, hang off their hind legs like overstuffed saddlebags. At has been found in previous research that the force necessary to dislodge a pellet was about 20 times more than the force a bee typically experiences while flying.
“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,” said 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.”
Bees use their long, straw like tube tongues (called a proboscis) to suck the nectar out of the flower and store it in their “honey stomachs.” This is separate from, and in front of, it’s digestive stomach and is used only for storing nectar. The honey stomach holds almost 70 mg of nectar and when full, it weighs almost as much as the bee does. Honey bees must visit between 100 and 1500 flowers in order to fill their honey stomachs.
In a study published March 26 in the journal Nature Communications and sponsored by the Air Force Office of Scientific Research, the researchers described how those two natural liquids work together to protect the bee’s bounty as it travels back to its hive.
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 said. “The oil separates the syrup from the air and slows down drying considerably.”
“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 said. “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 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 said.
Article source; http://www.rh.gatech.edu/news/619730/adhesive-formed-bee-spit-and-flower-oil-could-form-basis-new-glues
Research paper; Humidity-tolerant rate-dependent capillary viscous adhesion of bee-collected pollen fluids https://doi.org/10.1038/s41467-019-09372-x
