“A rose is a rose is a rose,” goes the poem by Gertrude Stein. Perhaps now we should revise that famous verse to add, “except when it’s a water purification device.”
A story published in the University of Texas at Austin’s UT News reports that a new device for collecting and purifying water, inspired by an origami rose, is a dramatic improvement on current methods. It could have many applications in the developing world and wherever clean water is scarce.
A team led by associate professor Donglei Fan in the Cockrell School of Engineering’s Walker Department of Mechanical Engineering developed a new approach to solar steaming for water production, a technique that uses the sun’s energy to separate salt and other impurities from water through evaporation.
The new solar steamer is made from layered, black paper sheets shaped into a 3D rose formation. The paper petals are attached to a stem-like tube. As the tube collects untreated water from any source, the paper’s shape makes it easier for the structure to collect and retain more liquid.
In a paper published in the most recent issue of the journal Advanced Materials, the authors outline how an origami rose provided the inspiration for the device. “We were searching for more efficient ways to apply the solar-steaming technique for water production by using black filtered paper coated with a special type of polymer, known as polypyrrole,” Fan is quoted as saying.
Polypyrrole is a material known for its photothermal properties. That means it’s especially good at converting solar light into thermal heat.
The new device is a breakthrough, because current solar-steaming technologies are expensive, bulky and produce limited results. The team’s method uses inexpensive materials that are portable and lightweight. Each roseate structure costs less than two cents and is capable of producing over half a gallon of water an hour per square meter.
It looks like a black rose in a glass jar, but the technical description for the revolutionary device is “a portable low-pressure controlled solar-steaming-collection unisystem.”
To see which were best at retaining water. Fan and her team experimented with a number of different shapes. First, they placed single, round layers of the coated paper flat on the ground under direct sunlight. Though these single sheets showed promise as water collectors, the amount gathered was not in sufficient amounts.
After toying with a few other shapes, Fan was inspired by a book she’d read in high school, Alexandre Dumas’ “The Black Tulip.” It gave her the idea to try a flower-like shape, and the spiral petal system of the classic rose turned out to be ideal. Its structure allowed more direct sunlight to hit the photothermic material with more internal reflections than any other floral shapes. It also provided an enlarged surface area for water vapor to dissipate.
Water is collected through the device’s stem-like tube and feeds it to the flower-shaped structure on top. It can also collect raindrops from above. Water finds its way to the petals where the polypyrrole material coating the “flower” turns the water into steam. When condensed in this way, Impurities naturally separate from water.
“We designed the purification-collection unisystem to include a connection point for a low-pressure pump to help condense the water more effectively,” the story quotes Weigu Li, a Ph.D. candidate in Fan’s lab and the paper’s lead author, as saying. “Once it is condensed, the glass jar is designed to be compact, sturdy and secure for storing clean water.”
The paper rose device removes contamination by heavy metals and bacteria. It also functions as a mini desalination plant, as it can extract salt from seawater, producing clean water that meets the drinking standard requirements set by the World Health Organization.
“Our rational design and low-cost fabrication of 3D origami photothermal materials represents a first-of-its-kind portable low-pressure solar-steaming-collection system,” Li says in the paper. “This could inspire new paradigms of solar-steaming technologies in clean water production for individuals and homes.”
The team’s research was funded by the National Science Foundation and the Welch Foundation.