University of Rochester (Rochester, New York, USA) researchers are trying to develop a new class of lasers to quickly modify metal surfaces, which they believe could make metals water-repellent without using coatings, paints, or solvents.
Potential applications include deicer treatments for airplanes and large trucks; rust and corrosion prevention for exposed metal surfaces; and anti-microbial surfaces for surgical and medical facilities. However, researchers say for the technology to become commercially viable, the lasers must become more powerful.
John Marciante, an Institute of Optics professor, is working to address this with venture capital-backed technology group, FemtoRoc Corp. (Boca Raton, Florida, USA). His six-year contract has a budget of ~$10 million. “What they need is a high-powered, ultra-fast, femtosecond-class laser system with average power measured in kilowatts, rather than the tens of watts now commercially available,” says Marciante. “So, we need to scale up by over a factor of 10.”
The school’s hydrophobic technology uses ultra-short laser pulses to create an intricate pattern of microscale and nanoscale structures, giving the treated metal surfaces a new set of physical properties. While they say the technology has proven successful, they note that it takes about an hour in the laboratory to pattern a 1 in by 1 in (25.4 mm by 25.4 mm) metal sample using commercially available lasers.
To develop faster lasers, Marciante must address two challenges. One is that laser beams are usually confined in conventionally designed optical fibers, which are very small in core diameter. In scaling up the power, too much light becomes concentrated in the fiber’s core, and nonlinear properties proliferate, causing the laser beam to broaden or become modulated.
The second challenge is overheating. “You’re pumping the laser beam at one energy level, at one end, and then extracting it at a lower energy level, at the other end, and no process is 100% thermally efficient. So that extra energy ends up in the fiber. The fiber can get very hot, even to the point of melting,” Marciante says.
In addition to school research, Marciante plans to leverage a network of veteran global researchers, as well as fiber design and manufacturing vendors.
In the initial stages, Marciante has two key findings. One, he says, involves a proprietary larger core optical fiber with superior laser beam qualities that is compatible with the desired lasers. The second, he explains, is a way to reduce the non-linear effects in the core of the fiber. “In principal, if you cut fiber length in half, you can go to twice as much energy,” Marciante says. “The tradeoff is, you’re also dumping the heat into half as much space.”
“It’s a very exciting challenge,” Marciante concludes. “No one in the world has been able to do this specific kind of femtosecond laser treatment of metal surfaces.”
Source: University of Rochester, www.rochester.edu.