Light-powered wing flaps as long as the sun shines
One of the challenges in designing micro air vehicles (MAVs) lies in the fact that if their battery is large enough to provide much range, it's too heavy for them to carry. Scientists have developed what could be an alternative, though, in the form of a sun-powered flapping wing.
Created by a team from China's Changzhou and Jiangsu universities, the "flexible bio-butterfly-wing" (FBBW) is constructed of a thin polymer sheet, that's coated on top with a nanocrystalline metallic film. The prototype device is laid out horizontally, with one end secured to a fixed support, and the other one free to move around.
When simulated sunlight is shone upon the FBBW, the temperature of its two materials increases, causing them to expand. Because the underlying FEP (fluorinated ethylene propylene) polymer expands more than the metal film on top, however, the wing responds by curling inwards and upwards.
Once it has curled all the way up, the curved top section shades the rest of the FBBW, allowing it to cool and thus flatten back out. In this way, the device rapidly and repeatedly curls up and down, creating a flapping motion which is faster than that of actual butterfly wings.
In a demonstration of the system, the researchers created a light-powered spinning whirligig, a toy sailboat that moved across the water by flapping its sail, and a device that generated electricity via the flapping of a wing. And although no FBBW-equipped flying mini-robots have been created so far, that is indeed one of the conceivable future uses for the technology.
A paper on the research was recently published in the journal ACS Applied Materials & Interfaces. The demo devices can be seen in action, in the video below.
Source: American Chemical Society