Search

In this study, we experimentally studied the relationship between wingbeat frequency and resonant frequency of 30 individuals of eight insect species from five orders: Odonata (Sympetrum flaveolum), Lepidoptera (Pieris rapae, Plusia gamma and Ochlodes), Hymenoptera (Xylocopa pubescens and Bombus rupestric), Hemiptera (Tibicen linnei) and Coleoptera (Allomyrina dichotoma). The wingbeat frequency of free-flying insects was measured using a high-speed camera while the natural frequency was determined using a laser displacement sensor along with a Bruel and Kjaer fast Fourier transform analyzer based on the base excitation method. The results showed that the wingbeat frequency was related to body mass (m) and forewing area (Af), following the proportionality f ~ m(1/2)/Af, while the natural frequency was significantly correlated with area density (f0 ~ mw/Af, mw is the wing mass). In addition, from the comparison of wingbeat frequency to natural frequency, the ratio between wingbeat frequency and natural frequency was found to be, in general, between 0.13 and 0.67 for the insects flapping at a lower wingbeat frequency (less than 100 Hz) and higher than 1.22 for the insects flapping at a higher wingbeat frequency (higher than 100 Hz). These results suggest that wingbeat frequency does not have a strong relation with resonance frequency: in other words, insects have not been evolved sufficiently to flap at their wings' structural resonant frequency. This contradicts the general conclusion of other reports--that insects flap at their wings' resonant frequency to take advantage of passive deformation to save energy.

In keeping with the high interest in micro air vehicles, microfabrication technologies have been developed in an attempt to mimic insect wings via a membrane-vein structure. In this work, we present microfabrication techniques that mimic a beetle wing to construct a realistic vein-membrane structure. Full microfabrication processes as well as sophisticated manipulations are introduced for constructing a realistic artificial wing whose key morphological and mechanical parameters can be achieved close to those of the real wing. Secondly, for wing loading reduction whenever moist air is present, we successfully fabricated superhydrophobic nanopillar forests by conventional nanofabrication techniques, such as ion beam and heat treatments. The creation of the nanopillar forests, which exist on the surface of leaves and insect wings, allowed lowering the dispersive component in a hydrophobic material, and the clustered nanopillars enhanced water repellency.