In addition to absorbing light across a broad wavelength range, the surface of the energy-absorbing aluminum surface in the system is superwicking (hydrophilic). When researchers angled it to face a light source, the metal surface drew a thin film of water over itself in an upward direction against gravity. The surface retained nearly 100% of the light energy it absorbed. As it heated the water, evaporation intensified, and the water’s intermolecular bonds changed.
As water evaporates and becomes a gas, it loses many of the potentially harmful contaminants it may contain, such as heavy metals. This makes solar-based purification methods an appealing option for purification; simply boiling water fails to remove heavy metals and other harmful contaminants, as water does not enter a gaseous state.
Unfortunately, solar-based methods are not always efficient in practice. Volume heating, as its name suggests, involves heating a large quantity of water — though only to a point that its top layer evaporates. From start to finish, volume heating uses only a small amount of the generated heating energy.
Another method, interfacial heating, places floating, multilayered absorbing and wicking materials on top of water. Though only water near the surface must be heated, all materials involved in the process must face away from the sun, in a nonvertical position.
As a result, Guo said, durability is vital to the new technology.
“The biggest advantage,” he said, “is that the angle of the panels can be continuously adjusted to directly face the sun as it rises, and then moves across the sky before setting. There was simply nothing else resembling what we can do here.”
Laser interactions and black metals
For Guo, work with lasers and the impact of their interactions on the surface properties of metals predates any of his laboratory’s discoveries with water and superwicking surfaces.
From 2005 to 2006, Guo’s research examined how intense femtosecond laser pulses influenced energy deposited over metal surfaces. The individual laser technologies Guo developed resulted in drastic changes to the optical responses of metal surfaces, to a point that in one application, laser pulses turned a shiny metal surface completely black.
As the black surface absorbs light across a broad wavelength range, it is a valuable resource for collecting light when, for example, building a thermal sensor.
Paired with the black surface’s…