Air-encapsulating elastic mechanism of submerged blowballs.

In this article, we report the observation of an air-encapsulating elastic mechanism of Dandelion spherical seed heads, namely blowballs, when submerged underwater. This peculiarity seems to be fortuitous since is living outside water; nevertheless, it could become beneficial for a better survival under critical conditions, e.g. of temporary flooding. The scaling of the volume of the air entrapped suggests its fractal nature with a dimension of 2.782 and a fractal air volume fraction of 4.82 × 10 m, resulting in nominal air volume fractions in the range of 14-23%. This aspect is essential for the optimal design of bioinspired materials made up of Dandelion-like components. The miniaturization of such components leads to an increase in the efficiency of the air encapsulation up to the threshold (efficiency = 1) achieved for an optimal critical size. Thus, the optimal design is accomplished using small elements, with the optimal size, rather than using larger elements in a lower number. The described phenomenon, interesting , also brings bioinspired insights toward new related technological solutions for underwater air-trapping and air-bubbles transportation, e.g. the body surface of a man could allow an apnea (air consumption of 5-10 l/min) of about 10 min if it is covered by a material made up of a periodic repetition of Dandelion components of diameter 18 μm and having a total thickness of about 3-6 cm.