With this article we are starting a new blog concept: – “theme sessions”. Every month a new theme will be defined and every Blogionik author will write an article based on its field of interest or experience. Therefore you can expect articles with different topics – but all related to the same theme. We would also like to invite specialists of particular themes to participate in our sessions in order to get a more detailed view on the subjects.
Our first theme is: LIGHT.
Probably the first association to light is the sun, since it provides natural light, necessary for all the life on Earth. During evolution, numerous systems to capture light have been developed by living organisms enabling them to adapt to different light conditions. Today, all these adaptations are inspiration for scientific research, constantly bringing up new discoveries.
In the field of Biomimetics, we are for instance interested in the variety of strategies for light harvesting or production by living organisms. We’d like to briefly introduce some interesting facts about light:
Sunlight is the most abundant energy source on this planet. However, the ability to convert sunlight into biological energy (in the form of adenosine-5′-triphosphate – ATP) is limited to chlorophyll-containing organisms (for example plants, algae, cyanobacteria). A lot of research is done on the topic of photosynthesis and main principles of photosensitation have already been described in one of our previous articles. But how can plants carry out photosynthesis when most of its photosynthetic tissue is hidden underground? Fenestraria rhopalophylla is an example (synonyms: babies’ toes, window plant). This plant is native to the Namibian desert, it commonly grows under sand, except for its transparent tips, allowing light to enter the leaves for photosynthesis. The plant produces optical fibers made from crystalline oxalic acid transmitting light to subterranean photosynthetic sites .
In order to capture as much light as possible, some plants, like sunflowers, developed light tracking systems and follow the sun throughout the day (Figure 1). How exactly light intensity triggers chemical signals and mechanical movements of plants will be described in one of our upcoming articles.
Light reaches Earth in different wavelengths, mainly in the visible spectrum. Apart from that, infrared light is a source of heat for many organism whereas the ultraviolet (UV) spectre can often be harmful. Of course nature would not be nature without its ingenious solutions to cope with challenges like that: for example via melanin. This is a natural pigment (also found in our hair and skin) that absorbs UV light and transforms it into heat. Respectively, melanin is able to dissipate 99.9% of absorbed UV radiation .
The ability to see UV light has evolved in many animal species to enhance their hunting or survival capabilities. An example are reindeers who can handle wavelengths down to around 350–320nm, which is termed ultraviolet. By using cameras that can pick up UV light, scientists noticed that some substances, organisms or material are absorbing UV light and are therefore appearing black, contrasting strongly with the snow. This includes urine – a sign of predators or competitors; lichens – a major food source in winter – and fur, making predators such as wolves very easy to see despite being camouflaged to other animals that can’t see UV .
Not only plants can harvest photons of light for energy production. Some animals, like hornets, have developed a type of solar cells inside their bodied to produce electricity . Pigments in the hornet’s yellow tissue trap light, whereas its brown tissues generate electricity. However, how hornets use this electricity is still not entirely understood.
Another extraordinary step in the evolution of life is to create own light where it does not exist in the surrounding, such as in boundless deep oceans. But this is not the only place were organisms produce their own light. Underground, in caves or forests, plants and animals exist which can produce light via bioluminescence. Bioluminescence is the production and emission of light by a living organism as the result of a chemical reaction during which chemical energy is converted to light energy. Bioluminescence aids the survival and reproduction of individual organisms through such means as camouflage and defence, attraction of prey and mates, and communication. More about this phenomenon will be presented in one of the upcoming articles.
Nature has many different principles which could change the way we perceive light. These mechanisms are not only providing inspiration for alternative light production, but also how we could harvest it in a more efficient way. Natural organisms could provide us with ideas for a more sustainable way to generate light and thereby to exclude non-renewable energy sources.
In the articles throughout the next four weeks we will, additionally to biological research on light, try to point out their biomimetic potential. Again we are kindly inviting you to contribute to our work with your own expertise (contact E-mail: email@example.com).
-  K.J. Niklas, H.C. Spatz, Plant Physics, 2012, The University of Chicago Press
-  P. Meredith , J. Riesz , Radiative relaxation quantum yields for synthetic eumelanin, 2004, Photochemistry and Photobiology. 79 (2): 211–6.
-  C. Hogg, M. Neveu et al., Arctic reindeer extend their visual range into the violet, 2014, Journal of Experimental Biology 214: 2014-2019
-  M. Plotkin et al., Solar energy harvesting in the epicuticule of the oriental hornet (Vespa orientalis), 2010, The Science of Nature 97 (12):1067-76
Cover image: AK Photography