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A D V A N C E D M A T E R I A L S & P R O C E S S E S | F E B R U A R Y / M A R C H 2 0 1 8 1 4 SURFACE ENGINEERING ANTIFOULING COATING CLEANS UP A group of scientists from Kiel University and Phi-Stone AG, both in Germany, won an international prize for their new environmentally-friend- ly marine antifouling coating. The long-lasting coating, which bested 119 other teams from three continents to win the Global Marine Technology En- trepreneurship Competition, requires no solvents and does not release pol- lutants into the ocean—unlike the cop- per-containing coatings currently in widespread use. Not only does the new coating deter organisms like barnacles andmussels fromsticking to the hulls of ships, it also allows easy removal of any creatures that manage to hitch a ride. The paint acquires its growth-reduction properties from a polymer composite that includes polythiourethane and ce- ramic particles, which also improve its mechanical properties and ability to adhere to a ship hull. When the bio-cor- rosion-resistant coating was tested on actual ships, researchers measured sig- nificantly less fouling than is typical after two years, and any growth that did occur was easy to wipe off with a plain sponge. Biofouling increases the amount of fuel ships use by up to 40% and costs the world’s transport industry over $150 billion per year. In an era when many polluting protective paints have been outlawed, and today’s wide- ly used copper-base compounds are expected to be prohibited in the near future, the new coating could serve a steeply growing demand. uni-kiel.de, phi-stone.de. NEW STAINLESS SURFACE STICKS IT TO BACTERIA By electrochemically etching a common stainless steel alloy, research- ers at Georgia Tech, Atlanta, developed a nanotextured surface that not only kills bacteria but increases corrosion re- sistance. The team applies electric cur- rent to samples of 316L stainless steel submerged in a nitric acid etching solution. The process shifts elec- trons from the surface into the electrolyte, leaving it textured like a mountain range with deep valleys and spi- key 20-25 nm peaks. Experiments show that 48 hours after expo- sure to bacterial cells, Scanning electron microscope images show the difference in adhesion of E. coli bacteria. Stainless steel sample on left is untreated, while sample on right is treated to create a nano- textured surface. Courtesy of Yeongseon Jang/Georgia Tech. the treated metal hosted significantly fewer bacteria compared to untreated controls, and many of those bacteria were dead. Further experiments show that mammalian cells, which are an order of magnitude larger than the bac- teria, remain undamaged on the treat- ed surface. The researchers believe that the nanoscale protrusions on the surface kill the miniscule bacteria by puncturing their cell membranes. The nanotexturing has another benefit as well—it increases the surface segrega- tion of chromium and molybdenum, improving corrosion resistance. Unlike antimicrobial films, this new technology—which could be used to prevent contamination on implant- able medical devices and food pro- cessing equipment—should provide permanent antimicrobial defense, and because it appears to rely on a bio- physical rather than chemical process, bacteria should not be able to develop resistance to it. Finally, electrochemi- cal etching is scalable and tunable. The team found that specific voltages and current densities control the type and scale of surface features. gatech.edu . BRIEF Praxair Inc., Danbury, Conn., and GE Aviation, Evendale, Ohio, opened a new Ellisville, Miss., facility for PG Technologies —a joint venture between Praxair Surface Technologies Inc., Indianapolis, and GE Aviation that specializes in advanced coatings for jet engines. The new 300,000-sq-ft facility is expected to house at least 250 employees to meet demand for the latest generation of jet engines, including the GE9X and the CFM LEAP. praxair.com , geaviation.com . Biologist Martina Baum of Kiel University applies a new environmentally-friendly antifouling coating. Courtesy of CAU.