Rose Shape Inspires Engineering Breakthrough At UT-Austin

AUSTIN, Texas — A rose by any other name would smell as sweet. But who knew its shape would inspire a revolutionary new way of collecting and purifying water? Taking root at the University of Texas at Austin, that idea has since blossomed.

A new device for collection and purification of water has been developed at the school, yielding a dramatic improvements on current methods. To boot: Each flower-like structure costs less than 2 cents to make, and can product produce more than half-a-gallon of water per hour per square meter, university officials added.

A team led by associate professor Donglei (Emma) 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 utilizing energy drawn from sunlight to separate salt and other water impurities through evaporation.

The findings published in the most recent issue of the journal Advanced Materials, outlines how an origami rose proved the inspiration for developing a new kind of solar-steaming system made from layered, black paper sheets shaped into petals. Attached to a stem-like tube that collects untreated water from any water source, the 3D rose shape makes it easier for the structure to collect and retain more liquid, UT-Austin engineers reported.

The 2-cent cost of the contraptions is an added bonus given the invariably expensive nature of current solar-steaming technologies that also tend to be bulky and produce limited results, officials suggested. Conversely, the engineering team’s method uses inexpensive materials both portable and lightweight.

And then there's the cool factor: The device looks like a black-petaled rose encased in a glass jar.

Hardened or highly logical engineers not prone to be swayed by the inherent romance and beauty of a rose would, accurately, describe this device as a portable, low-pressure, controlled solar-steaming collection "unisystem," and they'd be absolutely correct albeit in a sterile, awe-devoid fashion. Its geometric, external form is merely the manifestation of a desired utilitarian outcome, such underwhelmed engineers might opine.

Ah, but this would be to disregard that dear perfection of the rose so well retained. What's more, university officials confirm the flower resemblance is no coincidence: “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 said.

An explanatory aside from university officials: Polypyrrole is a material known for its photothermal properties, meaning it’s especially adept at converting solar light into thermal heat.

In searching for the ideal shape for the structure, Fan and her team experimented with a number of different ways of shaping the paper toward achieving optimal water retention levels. They conveyed how the process began by placing single, round layers of the coated paper flat on the ground under direct sunlight. The single sheets showed promise as water collectors but not in sufficient amounts, engineers found.

Ultimately after such origami machinations, inspiration struck. After toying with a few other shapes, Fan was inspired by a book she read in high school — not about roses, mind you, but other flora. Memories of having read “The Black Tulip” by Alexandre Dumas gave Fan the idea to study a flower-like shape, and the rose shape was found to be ideal. Its structure allowed more direct sunlight to hit the photothermic material — with more internal reflections as an added benefit, she explained — than other floral shapes, providing enlarged surface area for water vapor to dissipate from the material.

Here's how it works: Water is collected through a stem-like tube en route to feeding it to the flower-shaped structure on top, while concurrently collecting overhead rain drops. The water then finds its way to the petals where the polypyrrole-coated "flower" turns the liquid into steam. Impurities naturally separate from water when condensed in this manner, engineers noted.

“We designed the purification-collection unisystem to include a connection point for a low-pressure pump to help condense the water more effectively,” Weigu Li, a Ph.D. candidate in Fan’s lab and lead author on the paper, said. “Once it is condensed, the glass jar is designed to be compact, sturdy and secure for storing clean water.”

The device removes any contamination from heavy metals and bacteria, engineers found. What's more, it removes salt from seawater, producing clean water that meets drinking standard requirements set by the World Health Organization.

Papers on engineering projects don't often yield compelling headlines, as the clunky "Portable Low‐Pressure Solar Steaming‐Collection Unisystem with Polypyrrole Origamis" title to the Advanced Materials article — authored by Li, Fan, Zheng Li and Karina Bertelsmann —astonishingly illustrates. Thankfully, Weigu Li breaks it down layman style: “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 said. “This could inspire new paradigms of solar-steaming technologies in clean water production for individuals and homes.”

Scientists have long turned to nature for inspiration in harnessing her ancient, wordless wisdom. To be sure, the latest example of the tactic at the UT-Austin is suffused with the sweet smell of success.

The research was funded by the National Science Foundation and the Welch Foundation. Read more in the Advanced Materials journal.