The soap bubbles can successfully pollinate a flower on fruit-bearing plants. (Image Credit: Eijiro Miyako)


Soap bubbles promoted pollination of a pear orchard by delivering pollen grains to targeted flowers, showing that it's capable of pollinating fruit-bearing plants. Scientists from the Japan Advanced Institute of Science and Technology in Nomi have developed a robotic pollinator in an effort to help supplement the work of the dying bee population. The team published their findings in the journal iScience on June 17th.


"It sounds somewhat like fantasy, but the functional soap bubble allows effective pollination and assures that the quality of fruits is the same as with conventional hand pollination," says Eijiro Miyako, an associate professor in the School of Materials Science at the Japan Advanced Institute of Science and Technology. "In comparison with other types of remote pollination, functional soap bubbles have innovative potentiality and unique properties, such as effective and convenient delivery of pollen grains to targeted flowers and high flexibility to avoid damaging them."


Previously, the researchers created a small toy drone capable of pollinating flowers, but it also came with a setback. Even though it measured just two centimeters long, the team had difficulty keeping it from destroying the flowers while it flew into them. Miyako then decided to come up with a better flower-friendly artificial pollination technique. His inspiration came to him while spending a day at the park, blowing bubbles with his son when a bubble gently burst onto his son's face.  Miyako realized the bubble's gentle structure is what makes them the perfect pollinator for flowers.


Each bubble contains 2,000 pollen grains, which are capable of successfully pollinating a flower when the bubble pops. (Image Credit: Eijiro Miyako)


Afterward, the team used optical microscopy to confirm that soap bubbles could carry pollen grains. Next, they sampled five surfactants to determine their effects on pollen activity and bubble formation. The neutralized surfactant lauranmidopropyl betain (A-20AB) turned out to be the best one of the bunch since it's able to promote improved pollen germination and the tube's growth, which is developed from each pollen grain after it's deposited on a flower.


Using an analysis of soap concentrations, the team conducted experiments to see how pear pollen grains performed in a 0.4% A-20AB soap bubble solution with an optimized pH and added calcium along with other ions to influence germination.  After pollinating for three hours, the pollen activity settled through the bubbles as they remained steady, while alternate approaches like pollinating via powder or solution weren't as effective.


The low-tech design consists of a bubble gun loaded with a pollen solution, which was fired onto a pear orchard, resulting in the distribution of pollen grains (2,000 per bubble). This allowed the flowers to pollinate and produce fruit.  The researchers then loaded an autonomous, GPS-controlled drone with functionalized soap bubbles, which were then fired at fake lilies from a height of two meters, hitting their targets 90% of the time while it moved at 2 meters per second. 


Even though this is a promising solution to pollination, other techniques need to be developed to make it more precise. Weather conditions can also play a role in how the soap bubbles succeed in pollination. Rain could wash the pollen-bearing bubbles off the flowers, while strong winds could blow them away.


"I believe that further innovative technologies, such as state-of-the-art localization and mapping, visual perception, path planning, motion control, and manipulation techniques would be essential for developing autonomous precision robotic pollination on a large scale," says Miyako.


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