Black butterfly wings inspire solar cell design
The ‘common rose’ butterfly of India (Pachliopta aristolochiae) has big wings with large black patches. The black absorbs the sun’s rays that help warm the butterfly in cool weather.
Researchers analyzed the wings under an electron microscope, and discovered that the scales which cover them have their surface cratered by a ‘disordered’ array of tiny holes.2
These nanoholes trap the incident solar radiation, allowing a maximum to be absorbed, over a wide range of both wavelengths and angles. Structures that manipulate light on a microscopic scale are called photonic. The hollow scales also make the wing lighter.
The same researchers were inspired to design a new model of solar cell based on the butterfly wing pattern. This comprised thin silicon sheets with microscopic holes. A problem with normal solar cells is keeping them pointed at the sun, which requires expensive motion hardware. But the butterfly wing absorbs from almost any angle—and so does this new solar cell. Indeed, it absorbs twice as much sunlight as previous designs.
And not only was the design inspired by the butterfly wings, but so was the manufacture. In living creatures, the development of photonic structures must be controlled precisely. And this is done by a phase separation of liquids that don’t mix (immiscible).3 So these researchers used a solution of two polymers; one polymer that formed the sheets, and another polymer immiscible with the first. The resulting phase separation that made the network of nanoholes was surprisingly quick; it took only five to 10 minutes.
While there is no question that the solar cells were designed, it’s notable that a report also refers to the ‘design’ and ‘architecture’ of the butterfly wings.3–4 So using the scientific principle of analogy, which Darwin used all the time, should we not assume that the butterfly wings also had a Designer or Architect?
References and notes
- Lepidoptera (moths and butterflies) all have tiny scales covering their wings, which provide insulation, or as here a more direct role in temperature control, plus patterns for e.g. camouflage, mimicry, etc. Return to text.
- Siddique, R.H. et al., Bioinspired phase-separated disordered nanostructures for thin photovoltaic absorbers, Science Advances 3(10):e1700232, 19 October 2017 | doi:10.1126/sciadv.1700232. Return to text.
- Dufresne, E.R. et al., Self-assembly of amorphous biophotonic nanostructures by phase separation, Soft Matter 5:1792–1795, 30 March 2009 | doi:10.1039/B902775K. Return to text.
- Yirka, B., Black butterfly wings offer a model for better solar cells, phys.org, 19 October 2017. Return to text.
- Copying designs from nature is the rapidly growing field of biomimetics—see creation.com/biomimetics. Return to text.