A bet on Harvard University's anti-fouling paint technology innovation

At a conference in Italy in 2013, Nicolas Vogel, then a postdoctoral fellow at Harvard University's Wyss School of Bio-Inspired Engineering and the John Paulson School of Engineering and Applied Sciences (SEAS) at Harvard University, published a paper on his team's research on sliding liquid injection porous surface (SLIPS) coating technology, claiming that the coating prevents almost anything from sticking to the structural surfaces it coats.I bet mussels will stick to your paint because I haven't seen the surfaces they won't attach to, " Ali Miserez, associate professor of materials science and engineering at Nanyang Technological University (NTU) in Singapore, who specializes in biomass research, told Vogel.Vogel accepted the challenge, and when he returned to Cambridge, he sent some SLIPS samples to Miserez and launched a collaboration
China
. The results, published recently in the journal Science, show that SLIPS for specific structures does have the function of preventing mussels from adhesion, and reveals the coating behavior that prevents mussels from having the ability to adhere."I admit to losing the game," Miserez said. " mussels are one of the "culprits" of biological contamination or accumulation of organisms on the surface of underwater structures such as pipes, ships, industrial equipment and docks. Such biota are not only a threat to cut swimmers' feet, but also a major economic and environmental hazard, with the U.S. Navy alone spending nearly $1 billion a year on anti-fouling efforts, and many species invading new environments by attaching them to hulls.The most important weapons currently deployed against mussels and other adhesive organisms are paints and coatings containing toxic chemicals (usually copper-based) that can stop or kill organisms as they approach, but these materials have attracted attention because they indiscriminately poison species and accumulate in water, may have ecological implications and need to be replaced regularly and are often not as effective as expected.as an alternative, the industry has introduced non-toxic "low surface energy" coatings based on silicones or silica or fluoropolymers, similar to coating compounds used in catheters in the medical industry. Although these materials do allow for easier removal of biological defacement, their properties determine that they do not effectively prevent the attachment of organisms from the very beginning, but often require the movement of substrate objects to separate the attached organisms, in addition to the coating system is also vulnerable to damage and degradation failure.。 The Wyss Institute's SLIPS technology is inspired by the smooth "lips" of plant surfaces that prey on organisms, which slide insects down and transport them, taking full advantage of the principle that organisms are very difficult to attach to liquid surfaces. The LIQUIDS-coated solid surface consists of a covering layer injected with liquid lubricants, which can be maintained in a fixed and appropriate position, allowing any substance in contact with the liquid layer to be stripped off directly by sliding.。 SLIPS technology has previously been proven to be effective in the fight against bacteria and algae, but mussels represent a particular species of muscle foot that produces viscous wire called foot wire, and its tip (called bonding point) contains a special adhesive protein that removes water molecules from the target surface it touches so that the tip can be combined with the substrate surface.。 "The mussels have mastered the skills to stick to the underwater environment, even though water is the biggest enemy of adhesion," Miserez said. The mussel attachment mechanism allows it to bind very well to the substrate surface, and the accumulation of mussels can lead to weight gain of up to 1,700 pounds per square foot.In order to investigate whether SLIPS coatings can be adapted to mussels, a particular source of biological contamination, the NTU team, led by Miserez, placed Asian green mussels on a water base panel with a "checkerboard" pattern on the surface of different types of non-killing anti-fouling coatings, and observed the location of the mussels' selection. Two different types of SLIPS injected with silicone oil were evaluated: a 2-D coating consisting of very thin silicone nanostructures consisting of layered overlays (i-LBL) and a thicker matrix-compliant 3-D coating made of common polymers (polydmethylsiloxane) (i-PDMS). Coatings using non-lubricant injection technology include tungsten oxide-based 2-D coatings, uncoated glass, and two commercially available non-killing biota (Intersleek 700 and Intersleek 900).24 hours later, the results showed that the Intersleek 700-coated panel had an average of about 75 mussels per block, while only one of the 15 i-PDMS-coated panels had mussels attached and only five mussels, indicating that mussels were almost non-adheretable to the i-PDMS surface.Three anti-fouling coating models of different systems soaked in the surface of Thecituate sea in Massachusetts for 8 and 16 weeks NTU researchers are continuing their research to determine why mussels are not easily adhered to the surface of i-PDMS: the foot wire itself cannot adhere? and/or mussels refuse to adsorption on their surfaces?To answer the first question, the team measured the force required to pull the mussel's foot wire from each surface and found that the force required to pull the foot wire connected to the Intersleek coating was two to six times the force required to pull the filament from the i-PDMS coating surface, while pulling the foot wire from the non-injectable coating surface required 10 times the force., according to the researchers, this may be because the surface liquid coating injected by the lubricant resists the displacement of the mussel adhesive protein, maintaining surface lubrication and thus preventing the binding of the foot wire. In fact, when detailed biochemical analysis of mussel footprints was performed, the biomodulue characteristics of adhesive proteins were found on all control coating surfaces.to see if mussels continued to try to secrete foot silk, the researchers placed them on the surface of each model and observed them in real time. On impermeable LBL and PDMS surfaces, mussels behave normally, detecting them with their feet for a few seconds before secreting the foot wire, and then forming the foot wire in about 30 seconds. However, on a two-dimensional sliding surface, the detection takes 30 to 80 seconds and does not continue to secrete the foot wire, while on the i-PDMS surface several abnormal behaviors are shown: they choose to attach the foot wire to their shells or adjacent non-SLIPS coated surfaces;the researchers point out that in addition to damaging the foot wire itself, the surfaces injected by the lubricant confuse mussels, causing them to determine that they are not effective attachment positions.Scientists have been hoping that the lubrication layer of the SLIPS coating will physically interfere with the mussel's ability to determine the presence of a solid surface beneath it, as studies have found that the mussel's feet contain proteins known to sense stress, using a tiny bonding point to measure the force of "feeling" by touching and releasing different surface materials. On the surface of the SLIPS coating, the "pull force" measured by this contact makes it impossible for mussels to know exactly the solid surface under the coating."We know that mussels are expected to feel the pressure of hard surfaces on their feet, but this unexpected pull from lubricants seems to make them not want to attach foot wire, and in addition to the destruction of the foot wire binding mechanism by SLIPS, i-PDMS produces a stronger pull force than 2-D SLIPS, making it a better cover for the reality of the underlying hard surface."。 The Wyss team, in collaboration with the National Oceanic and Atmospheric Administration's (NOAA) Stellwagen Bank National Marine Sanctuary in Scituate, Massachusetts, immersed all laboratory-tested material in the port for 16 weeks to see if organisms would grow on its surface.this field laboratory is a typical North Atlantic bio-pollution area, the most famous source of which is a blue mussel (Mytilus edulis), so the results obtained by the laboratory can be scientifically compared with the results of experiments in the real world.
results show that the i-PDMS-coated model surface adheres to mussels not only four times less than Intersleek, but also 30 times less than non-permeable PDMS-coated model-attached mussels, while also showing significant advantages in the anti-fouling capacity of other biota, such as sacs, waterworms and mucus." experiment site, there are many organisms using different strategies of adhesive material to try to attach themselves to the surface of the model, but our experimental results show that the same solution can be effective for most organisms."more importantly, i-PDMS can be chemically modified to keep large amounts of lubricant stored in the polymer network, allowing the liquid cover to be continuously replenished to form long-lasting, high-performance anti-fouling coatings.the Wyss team is currently testing five other marine areas around the world with high bio-pollution characteristics, and so far, the test samples have maintained the ability to block mussels and other biological attachments for more than two years.
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