#chemical vapor deposition

Fabrics that resist water are essential for everything from rainwear to military tents, but conventional water-repellent coatings have been shown to persist in the environment and accumulate in our bodies, and so are likely to be phased out for safety reasons. That leaves a big gap to be filled if researchers can find safe substitutes.

Now, a team at MIT has come up with a promising solution: a coating that not only adds water-repellency to natural fabrics such as cotton and silk, but is also more effective than the existing coatings. The new findings are described in the journal Advanced Functional Materials, in a paper by MIT professors Kripa Varanasi and Karen Gleason, former MIT postdoc Dan Soto, and two others.

“The challenge has been driven by the environmental regulators” because of the phaseout of the existing waterproofing chemicals, Varanasi explains. But it turns out his team’s alternative actually outperforms the conventional materials.

“Most fabrics that say ‘water-repellent’ are actually water-resistant,” says Varanasi, who is an associate professor of mechanical engineering. “If you’re standing out in the rain, eventually water will get through.” Ultimately, “the goal is to be repellent—to have the drops just bounce back.” The new coating comes closer to that goal, he says.

New calculations from theoretical physicists at Rice University show it may be possible to guide the formation of 2-D boron by tailoring boron-metal interactions.

Rice University scientists have theoretically determined that the properties of atom-thick sheets of boron depend on where those atoms land.

Calculation of the atom-by-atom energies involved in creating a sheet of boron revealed that the metal substrate – the surface upon which two-dimensional materials are grown in a chemical vapor deposition (CVD) furnace – would make all the difference.

Theoretical physicist Boris Yakobson and his Rice colleagues found in previous work that CVD is probably the best way to make highly conductive 2-D boron and that gold or silver might be the best substrates.

But their new calculations show it may be possible to guide the formation of 2-D boron by tailoring boron-metal interactions. They discovered that copper, a common substrate in graphene growth, might be best to obtain flat boron, while other metals would guide the resulting material in their unique ways.