If you don't want to die of thirst in the desert, be like the beetle. Or have a nanotube cup handy.
New research by scientists at
The invention they call a "hygroscopic scaffold" is detailed in a new paper in the
Researchers in the lab of
They modified carbon nanotube forests grown through a process created at
"It doesn't require any external energy, and it keeps water inside the forest," said graduate student and first author Sehmus Ozden. "You can squeeze the forest to take the water out and use the material again."
The forests grown via water-assisted chemical vapor deposition consist of nanotubes that measure only a few nanometers (billionths of a meter) across and about a centimeter long.
In tests, water molecules bonded to the hydrophilic top and penetrated the forest through capillary action and gravity. (Air inside the forest is compressed rather then expelled, the researchers assumed.) Once a little water bonds to the forest canopy, the effect multiplies as the molecules are drawn inside, spreading out over the nanotubes through
The researchers tested several variants of their cup. With only the top hydrophilic layer, the forests fell apart when exposed to humid air because the untreated bottom lacked the polymer links that held the top together. With a hydrophilic top and bottom, the forest held together but water ran right through.
But with a hydrophobic bottom and hydrophilic top, the forest remained intact even after collecting 80 percent of its weight in water.
The amount of water vapor captured depends on the air's humidity. An 8 milligram sample (with a 0.25-square-centimeter surface) pulled in 27.4 percent of its weight over 11 hours in dry air, and 80 percent over 13 hours in humid air. Further tests showed the forests significantly slowed evaporation of the trapped water.
If it becomes possible to grow nanotube forests on a large scale, the invention could become an efficient, effective water-collection device because it does not require an external energy source, the researchers said.
Ozden said the production of carbon nanotube arrays at a scale necessary to put the invention to practical use remains a bottleneck. "If it becomes possible to make large-scale nanotube forests, it will be a very easy material to make," he said.
Co-authors are postdoctoral researcher Liehui Ge, graduate student
TNS 18DejucosGrace-140612-30FurigayJane-4763839 30FurigayJane
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