The small dogfish lay in the drift line on the shores of the Finistère coast in northwestern France. Walking along the beach, Professor Antonia Kesel noticed the dead shark was barnacle-free, while other deceased sea dwellers are usually covered with marine growth. This discovery led Kesel to commit her life’s research to the potential applications of sharkskin.
Dogfish and sixgill sharks are observable to the people residing in the Puget Sound area, said Leo Bodensteiner, associate professor at Western Washington University. Almost two million dogfish are residents in Washington’s inland waters, according to 2001 statistics from the Florida Museum of Natural History.
Boats, submarines and aircrafts mimic the contours of sharks. The skin of these creatures is also being used as a model to develop coverings for the hulls of boats that could prevent the attachment and accumulation of marine creatures.
The University of Applied Science in Bremen, Germany is one of the places that synthetic sharkskin texture has been created using dogfish shark models. The group, with Prof. Kesel, who is head of the master program of biomimetics at the university, works for shipbuilding and applied science. Katrin Mühlenbruch, assistant professor at the university, said applying artificial sharkskin to boat hulls prevents biofouling, the accumulation of organism growth. The engineered surface results in less fuel consumption and CO2 emission to the environment.
Unlike most fish scales, which are flat and smooth, shark scales have a texture similar to sand paper, Bodensteiner said. Shark scales, called dermal denticles, are arranged in a microscopic diamond pattern. Each scale has one principle spike protruding out of its center. This creates tiny drag points on the sharkskin instead of one larger drag point that pushes through the water. Small drag points help to reduce drag and allow sharks to swim faster and easier than other fish, Bodensteiner said.
In addition, the roughness of sharkskin makes it difficult for bacteria and marine organisms to adhere to its surface.
Sharklet Technology LLC, a spin-off company from the University of Florida, has been using the model of a Galapagos sharks’ skin pattern for engineered sharkskin. Two hypotheses for why the design works have emerged.
First, the surface creates an energetically unstable area for the bacteria. The energy that it would take for the organism to establish a home on the surface is more than it is willing to expend, so the organism will leave to find another place to settle.
Second, the surface would halt the grouping of barnacles and other marine organisms by not allowing them to send signals to each other, said Mark Spiecker, vice-president of Sharklet Technology.
"The major task of barnacle larvae is to find a place to settle where the adult will survive," said Dr. Brian Bingham, a professor of environmental science at Western.
They like dark places to settle, such as the bottom of ships, he said.
The idea of this technology is to mimic sharkskin structure. This is a non-toxic way to delay the attachment of fouling organisms. The material contains manmade gradients that copy sharkskin patterns.
The engineered surface is made of a variety of microscopic-sized surface structures in a diamond shape. These structures are smaller than a human hair and 10 times smaller than the actual size of sharkskin, Spiecker said.
Submerged surfaces of boats, ships and ferries can be the perfect environment for marine organisms such as barnacles, slime and algae to grow. Such marine biofouling increases drag resistance and reduces speed, resulting in extra maintenance that can cause up to a 40 percent increase in fuel costs for ships, according to the International Maritime Organization (IMO).
To prevent biofouling, most boat owners use anti-fouling paints: paints designed to inhibit sea creatures’ growth. Many do this by leaching their toxic chemicals into the water. Copper paints are used as a biocide to kill marine life, said Kevin C. Fitzpatrick, water quality section manager of the Department of Ecology. Copper-based paints have been used more widely since tributyltin (TBT) paints were banned due to their highly toxic nature, said Phil Riise, CEO of Seaview Boatyard East.
Synthetic sharkskin surfaces have micro-sized diamond shapes carved out of non-toxic silicon wafers. On the diamond-shaped topographies, the marine organisms can only reach a maximum of three contact points. Since they prefer more than three contact points to get a better grip, organisms are discouraged from growing on the surface.
Synthetic sharkskin can be applied to more than boats, Spieker said. The material could also be used on high chairs, toilet seats and wallpaper to reduce bacterial buildup. He said the solution of making a texture to apply to boat hulls is in progress. Since this product is not currently on the market, the price of it has yet to be determined, Spieker said.
"It could be applied to anywhere you would like to keep macroorganisms from growing," Spieker said.
Synthetic sharkskin could also combat growth of microorganisms. Application to hospital equipment has the most potential for being on the market at the end of this year, Spiecker said. Currently, the application to hygienic surfaces is under field trial at some hospitals. The engineered surface could be embedded or could be directly imprinted into a device or a piece of equipment such as a catheter, Spiecker said. Synthetic sharkskin could impair bacterial growth on the equipment the same way it discourages barnacles to attach to boats, reducing the potential for growth of bacteria like Staph and E. coli and limiting the spread of disease.
This eco-friendly approach could help eliminate the need for anti-fouling paints, benefiting human and marine ocean travelers, said Dr. Ruth M. Sofield, assistant professor of Environmental Sciences at Western.
"If you have something that is not allowing chemicals to reach into the marine environment, it is a better scenario for the marine environment," Sofield said.
Kwihwa Lee is a journalism major. She has been published in The Western Front, Klipsun and The North American Post.