April 01, 2019
So it seems that scientists are looking to turn bee spit and flower oil into glue. No, this is not an April Fools' Day joke! It's science.
Learn about this and more interesting stories from the scientific community in today's issue.
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*-- Scientists look to turn bee spit and flower oil into glue --*
Bees have many talents. They're highly organized, adept flyers and excellent navigators. According to a new study, they're also masters of adhesion.
As bees collect tiny bits of pollen from flowers, they compact the powdery grains into bundles attached to their hind legs. But what keeps the balls of pollen from washing away in a rain storm?
According to scientists at the Georgia Institute of Technology, the combination of bee spit and flower oil ensure the pollen bundles remain firmly in place.
"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," J. Carson Meredith, a professor of chemical and biomolecular engineering at Georgia Tech, said in a news release. "Being able to withstand those kinds of changes in humidity is still a challenge for synthetic adhesives."
Through a series of detailed observations and lab tests, scientists were able to explain how bee spit and flower oil combine to bind pollen to bee legs and protect it from the elements.
First, the bee's salivary glands produce a secretion that coats each pollen grain, causing them to bind together. Bees use sugar from the flower nectar they drink to produce the special saliva. The sticky saliva also helps the bundles adhere to the bees leg.
The second substance, the flower oil, or pollenkitt, protects the adhesive qualities of the saliva, ensuring it's stickiness isn't compromised by varying humidity levels.
"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."
In the lab, scientists separated the two components and studied how bee saliva, without the protection of pollenkitt, reacted to different humidity levels. The tests showed the nectar-based secretion absorbs more water as humidity levels rise, weakening the substance's adhesive qualities.
When they added pollenkitt back to the mix, the sticky saliva remained unaffected by changing humidity.
The researchers estimate the combination could be replicated to form new kinds of bio-inspired glues -- glues that are more resilient and less vulnerable to harsh environments and changing weather.
"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."
Meredith and his colleagues published their analysis of bee spit and flower oil in the journal Nature Communications.
*-- 3D printer deposits electronic fibers on fabrics --*
To make wearable electronics, one group of researchers in China has developed a 3D printer that deposits electronic fibers onto fabrics.
Most current methods for the production of smart clothes, or wearable electronics, involve manually sewing electrical components into fabrics. The multistep processes are time and labor intensive, making them more expensive and more difficult to scale.
Researchers at Tsinghua University in Beijing decided to save time and money by printing electronic fibers onto fabrics, instead of incorporating the electronic components into the clothes.
"We used a 3D printer equipped with a home-made coaxial nozzle to directly print fibers on textiles and demonstrated that it could be used for energy-management purposes," Yingying Zhang, a chemistry professor at Tsinghua, said in a news release. "We proposed a coaxial nozzle approach because single-axial nozzles allow only one ink to be printed at a time, thus greatly restricting the compositional diversity and the function designing of printed architectures."
The double nozzle allowed researchers to print a multilayer thread, composed of a conductive core and an outer insulating layer of silkworm silk. Scientists attached the injection syringes filled with the two inks to the coaxial nozzle and integrated the combination with a 3D printer.
For the proof-of-concept tests, researchers used the 3D printing technology to print designs on squares of fabric. The approach worked, and it was cheaper and faster. But the technology's precision and the complexity of its designs are limited by the accuracy of the printer's mechanical movements, as well as the size of its nozzles.
"We hope this work will inspire others to build other types of 3D printer nozzles that can generate designs with rich compositional and structural diversity and even to integrate multiple co-axial nozzles that can produce multifunctional E-textiles in one-step," Zhang said. "Our long-term goal is to design flexible, wearable hybrid materials and electronics with unprecedented properties and, at the same time, develop new techniques for the practical production of smart wearable systems with integrated functions, such as sensing, actuating, communicating, and so on."
Researchers described their 3D printing efforts in a new paper published this week in the journal Matter.
Last year, scientists at the University of California, San Diego used a 3D printer to produce stretchable electronics that can be integrated into smart clothes.