An environmentally
friendly superhydrophobic coating repels water as effectively as
commercial
coatings that employ hazardous materials, according to scientists at Rice
University and
the University of
Swansea. (Credit: Shirin Alexander/University of Swansea)
(December 10, 2015) ‘Green’
project led by Rice, Swansea scientists matches best water repellant.
A new class of superhydrophobic nanomaterials might simplify
the process of protecting surfaces from water.
A material made by scientists at Rice University, the
University of Swansea, the University of Bristol and the University of Nice
Sophia Antipolis is inexpensive, nontoxic and can be applied to a variety of
surfaces via spray- or spin-coating.
The researchers led by Rice chemist Andrew Barron reported
their find in the American Chemical Society journal ACS Applied Materials and
Interfaces.
The hydrocarbon-based material may be a “green” replacement
for costly, hazardous fluorocarbons commonly used for superhydrophobic
applications, Barron said.
“Nature knows how to make these materials and stay
environmentally friendly,” Barron said. “Our job has been to figure out how and
why, and to emulate that.”
The lotus leaf was very much on their minds as the
researchers tried to mimic one of the most hydrophobic — water-repelling —
surfaces on the planet. Barron said the leaf’s abilities spring from its
hierarchy of microscopic and nanoscale double structures.
“In the lotus leaf, these are due to papillae within the
epidermis and epicuticular waxes on top,” he said. “In our material, there is a
microstructure created by the agglomeration of alumina nanoparticles mimicking
the papillae and the hyperbranched organic moieties simulating the effect of
the epicuticular waxes.”
A scanning
electron microscope image of a new superhydrophobic material shows
the rough surface
of functionalized alumina nanoparticles. Scientists at Rice University
and the University
of Swansea led the creation of the environmentally friendly material.
(Credit:
University of Swansea)
Fabrication and testing of what the researchers call a
branched hydrocarbon low-surface energy material (LSEM) were carried out by
lead author Shirin Alexander, a research officer at the Energy Safety Research
Institute at the Swansea University Bay Campus.
There, Alexander coated easily synthesized aluminum oxide
nanoparticles with modified carboxylic acids that feature highly branched hydrocarbon
chains. These spiky chains are the first line of defense against water, making
the surface rough. This roughness, a characteristic of hydrophobic materials,
traps a layer of air and minimizes contact between the surface and water
droplets, which allows them to slide off.