Water covers most of the globe, yet many regions still suffer from a
lack of clean drinking water. If scientists could efficiently and
sustainably turn seawater into clean water, a looming global water
crisis might be averted. Now, inspired by origami, the Japanese art of
paper folding, researchers have devised a solar steam generator that
approaches 100 percent efficiency for the production of clean water.
They report their results in
ACS Applied Materials & Interfaces.
Solar steam generators produce clean water by converting energy from
the sun into heat, which evaporates seawater, leaving salts and other
impurities behind. Then, the steam is collected and condensed into clean
water. Existing solar steam generators contain a flat photothermal
material, which produces heat from absorbed light. Although these
devices are fairly efficient, they still lose energy by heat dissipation
from the material into the air. Peng Wang and colleagues wondered if
they could improve energy efficiency by designing a three-dimensional
photothermal material. They based their structure on the Miura fold of
origami, which consists of interlocking parallelograms that form
“mountains” and “valleys” within the 3D structure.
The researchers made their solar steam generator by depositing a
light-absorbing nanocarbon composite onto a cellulose membrane that was
patterned with the Miura fold. They found that their 3D device had a 50
percent higher evaporation rate than a flat 2D device. In addition, the
efficiency of the 3D structure approached 100 percent, compared with 71
percent for the 2D material. The researchers say that, compared to a
flat surface, origami “valleys” capture the sunlight better so that less
is lost to reflection. In addition, heat can flow from the valleys
toward the cooler “mountains,” evaporating water along the way instead
of being lost to the air.