Moth Eyes and Cicada Wings for the Solar Cells and Windows of the Future !
What's the link between insects and solar cells? Bugs hold the secret - improved photocells.
Peng Jiang, an assistant professor of chemical engineering at the University of Florida, gets his inspiration from the eyes of moths and the wings of cicadas in developing new anti-reflective and water-repellent coatings, with huge potential for new more effective and self-cleaning solar cells, car and home windows, computer screens and other devices. "Nature is an amazing innovator. What I'm interested in doing is mimicking the structure of some remarkable biological systems for real-world use.", said Jiang.
Moth eyes are built up of adjacent hexagonal eyelets, each one filled with thousands of neat rows of tiny bumps (nipple-like protrusions). As each bump is less than 300 nanometers (300 billionths of a meter), only an electron microscope can visualize them.
*Moth eyes inspire self-cleaning antireflection nanotechnology coatings*
When moths fly at night, their eyes need to capture all the light available. To do this, certain species have evolved nanoscopic structures on the surface of their eyes which allow almost no light to reflect off the surface and hence to escape.
Now scientists at MicroBridge, a project at the Manufacturing Engineering Centre (MEC), have adopted the model to create an industrial lens for use in a low light environment.
The structures on the surface of the new lens are less than 100 nanometres in height (a nanometre is one millionth of a millimetre). They need to be smaller than the wavelength of light to avoid disrupting the light as it enters the lens.
The tiny features of the lens mould were created using the Centre’s Focused Ion Beam. The beam uses highly charged atomic particles to machine materials in microscopic detail.
Dr Robert Hoyle of the MEC said: “This was a particularly complicated challenge. Not only did the lenses have to be of very precise curvature but the nanoscopic structures on the lens surfaces had to be smaller than the wavelength of light so as to smooth out the sharp refractive index change as the light strikes the surface of the lens. This smoothing of the refractive index reduces the reflectiveness of the lens thus allowing it to capture more light. The end result has a number of highly practical uses for industry.”
The MEC and MicroBridge are now looking at using the lens in optoelectronics and photovoltaic applications in semiconductors, including solar cells, where loss of light is a major problem. The lens also has potential uses in fibre optics, sensors and medical diagnostic devices.