In a new paper published on 28 May in Advanced Materials, the authors report a novel water purification device inspired by a rose (1). The solar-steaming system is made from layered, black paper sheets shaped into petals encased in a glass jar as a novel portable water purification system. The “stem” is a tubular structure that collects untreated water from any source — including rain — which flows through the 3D petals. The system uses energy from sunlight to separate salt and other impurities from water through evaporation.
Clean water is critical to meet the demands of population growth and increased industrialisation and to improve the quality of life in the developing world. Greener technologies that make use of solar energy could help bring clean water, sanitation, and hygiene to communities while protecting precious natural resources.
The researchers from the University of Texas, led by Associate Professor Donglei (Emma) Fan, may have designed a more efficient way to apply the solar-steaming technique for water treatment. The technique uses energy drawn from the sun’s rays to separate salts and other water impurities from water through evaporation.
The black filtered paper coated with a special type of polymer called polypyrrole that can convert light to heat. Polypyrrole condenses water into steam and as this happens, impurities are separated from the water. The “unisystem” also connects to a low-pressure pump to help condense the water more efficiently.
Single sheets of the polypyrrole-coated paper cannot collect enough water. So the authors looked at various shapes in search of a design that would retain the optimal amount of water. Many devices take inspiration from nature and Fan remembered a book she read as a child called “The Black Tulip” by Alexandre Dumas.
They soon discovered that the origami-style rose is an ideal shape as it allows more direct sunlight to hit the material and also creates more internal reflections. The flower-like structure — and in particular, the rose — provides a larger surface area such that more water can evaporate from the material.
Another advantage of this approach is that it is much cheaper — just 2 cents to produce — and less bulky than existing systems. The inexpensive materials are both portable and lightweight, enabling the researchers to achieve “portable low-pressure solar steaming collection system with high performance”.
The device removes contamination from heavy metals and bacteria, as well as salt from seawater, leaving only purified water that meets drinking standard requirements of the World Health Organization. And it can product produce almost two litres of water per hour per square meter, which is then stored securely in the glass jar.
The authors write, “This work can inspire new paradigms toward developing high‐performance solar steaming technologies for individuals and households”. The novel low-cost device could help address the growing global scarcity of clean water.
(1) Li, W. et al. Portable Low‐Pressure Solar Steaming‐Collection Unisystem with Polypyrrole Origamis. Advanced Materials (2019). DOI: 10.1002/adma.201900720