Sponges, though it is still not clear whether they are plants or animals, are inspiring the solution to a problem which has troubled chemists for years.
Scientists were working on ways of obtaining complex micro or nano (a billionth of a meter) structures by using simple inorganic substances like silicon. Producing a micro-scale device such as a transistor required difficult and expensive processes such as cutting a silicon layer neatly. A species of sponge (tethya aurantia) has proved to be a model for a possible solution.
Like every other creature, sea sponges are given the ability to use chemical substances in the exact proportions they need to carry out their vital functions like an expert chemist. A sea sponge obtains siliceous acid from the water around it a few hundred meters under the sea. By a mechanism where chemical energy is used at high efficiency and silicatein enzyme functions as a catalyzer, this acid is transformed into silicon dioxide or silica, and perfect three-dimensional structures are built from it.
The most noteworthy aspect of this process is that there is no need for the poisonous chemicals or high temperatures scientists use to obtain complex inorganic structures. Sea sponges are granted the ability to build these complex structures far more effectively than the engineers who try to produce semi-conductive materials. When the outer tissue of a sponge is removed, the 2mm-long skeletal structure, which is thinner than human hair and which takes the form of glass needles, becomes visible.
Sponges fall into three categories with respect to the abundance of their cavities and the intricacy of the channels between them. Those with the maximum proportion of cavities and channels are the most desired ones. We can better understand how wonderful are the nano-scale structures within sponges by observing the relation between a sponge and water. When we dip a hand-size sponge in water and take it out, we see that it holds water equivalent to thousands of times more than its own weight. This is caused by the countless nano-cavities invisible to the naked eye within the body of the sponge. In these minute capillary distances, the adhesion and surface tension forces are given a dominant role between water and the substance of the sponge by the divine will. Sponges, which are classified as simple structured animals by some biologists, are granted some specialties to inspire us in making high technology products such as computer microchips and solar cells.
Daniel Morse and two of his colleagues from the University of California are working on some semi-conductive materials with amazing electronic features like turning daylight into electricity. The most important application field of this new technique will be more efficient photovoltaic solar cells. Presently, solar cells are produced under high temperatures and low pressure, which requires too much energy. However, the method taught to sea sponges is highly efficient and does not require high energy. Scientists have managed to produce simpler and cheaper solar cells by imitating sea sponges and using zinc oxide instead of silicon. This way the billion-dollar facilities where the semi conductive materials are produced can possibly be replaced by smaller units of production. The world of living beings has always opened doors to new horizons. Things we take for granted and to which we do not give much thought are waiting to be reflected upon and seen through the eye of wisdom.
- Paul Marks, Sea sponge leads way to cheaper solar cells, New Scientist, 24 March 2007, p. 32.