MIT Research Strives to Upgrade Hull Coatings
An American military agency is sponsoring research on the development of a hydrogel material that could help antifouling coatings stick to metal hulls better and longer.
Dr. Xuanhe Zhao, an associate professor at the Massachusetts Institute of Technology, led a team in creating an adhesive material that would also retain moisture and avoid the use of toxic chemicals and other pollutants, the Office of Naval Research reported.
The ONR is interested in Zhao’s work because foulants like clusters of barnacles on a ship’s hull can hinder its speed and increase its fuel consumption by 40 percent, the organization notes.
“Biofouling is a major concern for the Navy, leading to hundreds of millions of dollars a year in fuel and maintenance costs,” says Dr. Steve McElvany, a program manager in ONR’s Sea Warfare and Weapons Program, who oversees Zhao’s research.
“It’s especially bad when the ship is docked in port,” he adds. “Barnacles like those environments and tend to accumulate rapidly, in large quantities.”
Hydrogels Inspired by Skin
At this time, the Navy uses copper-based paints and coatings to kill barnacles or prevent them from attaching to hulls.
While effective, these materials are toxic and leach into the water, negatively affecting aquatic life, so the Navy is seeking environmentally friendly coatings options.
To that end, Zhao’s work is focused on the use of hydrogels—substances that can absorb water and hold it in the form of a gel, according to the ONR.
Extremely soft and slippery, they can be spread on a ship’s underside like a sealant, eliminating the hard, solid spots barnacles prefer and thus preventing them from sticking to the metal, the group explains.
Zhao’s research tackles the challenge of how to keep hydrogel coatings soft, wet and securely fastened to metal hulls.
Using a chemical bonding agent called benzophenone, his team developed a way to fuse hydrogels with elastomers—elastic polymers that are stretchy, durable and impervious to water.
Noting that the team’s approach was inspired by human skin, their end result is a sticky, water-trapping barrier that keeps hydrogels robust enough to potentially withstand the harsh hull conditions of a ship at sea, ONR says.
“The skin has an outer epidermis that protects nerves, capillaries, muscles and organs—and keeps them from drying out, maintaining their compliance,” Zhao says.
“However, we can actually stretch the hydrogel-elastomer hybrid to seven times its original length and the bond still holds,” he adds. “It’s that strong and flexible.”
ONR notes that the hybrid also has potential as a circuit for transporting ions, which could be used to detect the presence of barnacles on a hull. Once identified, a specially designed hydrogel could pump barnacle-repelling enzymes via grooves etched into the elastomer, it says.
Additionally, Zhao believes the hybrid material could also be used as a smart bandage outfitted with electronics and drug reservoirs—allowing it to monitor wounds and vital signs like body temperature, detect bacteria and administer antibiotics, and alert a doctor when more medicine is required.
“Our main focus is helping the Navy deal with the issue of biofouling,” says Zhao. “But it’s also exciting to think of the other possibilities for this material. This is still very basic research, but we envision numerous potential applications and uses for hydrogels and elastomers.”
Zhao is the 2014 winner of ONR’s Young Investigator Program, a prestigious grant awarded to scientists and engineers with exceptional promise for producing creative, state-of-the-art research that appears likely to advance naval capabilities.
The Office of Naval Research is an organization within the United States Department of Navy that coordinates, executes and promotes the science and technology programs of the U.S. Navy and Marine Corps. It celebrates 70 years of innovation this year.