It’s hard to find a paper or article these days that doesn’t begin with a reference to “Declines in the number of global pollinator insects” or some other form of the bee or insect ‘apocalypse’ sentiment and the potential economic or ecological damage to be wrought. While one reaction to this is to prevent or mitigate the circumstances that cause it, finding alternatives to natural biotic pollination is another one to consider. At times there are clear reasons why forms of ‘artificial’ pollination are valuable, but the cost of harvesting pollen to use, and the manual or mechanical means to deliver it are expensive and imperfect.
Two scientists at the Advanced Science and Technology in Japan have applied some ‘blue-sky’ thinking to the problem and come up with an unusual suggestion. They observe that is pretty easy to indiscriminately spread pollen around in an orchard, in fact the waste involved is a large part of the cost. Rather, a system must be gentle, precise, thrifty, and aerial, so what better to choose to deliver the pollen than bubbles!
They see bubbles with different eyes. Bubbles can be chemically functional, light-weight, steady-liquid, bilayer molecular membranes, low cost, and bio-degradable. The pollen grains can’t scatter as they are bound by the thin film, and the bubbles are easy to create and control in flight. They can’t damage the delicate parts of the flowers, but (it’s a good thing) they are somewhat sticky. It’s obvious really.
So the paper describes how they set out to show just how obvious it is. They needed to show the bubbles could be made, that they would work well as a pollinator, and that there was a practical way of controlling them. A ‘proof of concept’ was what they were attempting. This is how they describe the outcome;
“…we demonstrate that (1) chemically functionalized soap bubbles exhibit unique properties, such as delivering pollen grains to the targeted flowers in a simple manner, reducing the usage of pollen grains, effectively attaching soap bubbles on the pistils of the targeted flowers using the high stickiness of the soap bubble membrane, preventing severe damage to delicate flowers using the softness and high flexibility of soap bubbles, and enhancing the pollen activity by promoting germination ratio and length of pollen tube; (2) chemically functionalized soap-bubble-mediated pollination can be used for practical Pyrus pyrifolia var. culta pollination at orchards aside from its contribution toward the healthy expression of fertility for various pollen grains; (3) mechanically stabilized soap bubbles capable of withstanding windmills due to robotic pollination can be successfully prepared; and (4) an autonomous controllable unmanned aerial vehicle (UAV) equipped with a mechanically stabilized soap bubble maker can fully automatically transport pollen grains to Lilium japonicum flowers, thus successfully aiding in plant pollination.”
These weren’t just any old bubbles. They used a particular surfactant that aided bubble formation, but which did not harm growing pollen tubes, in proportion to the size and number of pollen grains it had to ‘host’ (2000/bubble – 4mg/ml). The liquid was the right pH, with added boron, calcium, magnesium, and potassium salts, proteins from Gelatine, and an inert, cellulose-based viscous polymer (your eye-drops) to fuel germination and control the properties of the bubble membrane. Truly ‘functional’ bubbles. The drone, and the bubble maker, were off-the-shelf toys, although, beyond the ‘proof-of-concept stage, you can imagine them being much more sophisticated, intelligent even.
Where will this end up? Probably nowhere, like 99% of such ideas, just creating more ideas. But that 1%? That 1% changes things.
Yang and Miyako, Soap Bubble Pollination, iScience (2020), https://doi.org/10.1016/j.isci.2020.101188