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Surface grooves on polymers enable waterproofing
Researchers from Kyoto University’s Institute for
Cell-Material Sciences (iCeMS), Japan, developed a
unique way to waterproof new functionalized materials
involved in gas storage and separation by adding exte-
rior surface grooves. The materials, known as porous co-
ordination polymers (PCPs), are hollow nanoscale,
cagelike structures that can house molecules within their
empty cavities. This behavior is particularly useful when
selectively isolating chemicals of interest from mixtures
such as gases, say researchers. However, one drawback of
using PCPs involves their use in environments where water is abundant.
“These materials are highly reactive with water, leading to their instability and subse-
quent decomposition,” explains materials scientist Masakazu Higuchi. “In order to use them
in real-life situations, we need to develop PCPs with the ability to keep water out while al-
lowing organic molecules of interest in.”
To do this, scientists designed grooves onto the exterior surface of the PCPs, thereby
introducing a rough texture that effectively repels water. At the same time, organic sub-
stances can enter the PCPs based on size, demonstrating selectivity.
“Our method is the first to be conducted at the nanoscale, and serves as a simpler means
to maintain functional properties of PCPs while preventing them from breaking down in
the presence of water,” notes iCeMS director and principal investigator Susumu Kitagawa.
Ultra-black coating holds promise for sensitive space instruments
A new super-black nanotechnology that aims to make spacecraft instruments more
sensitive without enlarging their size is being tested on the International Space Station
(ISS). The material is a highly uniform coating made of multi-walled carbon nanotubes. Ac-
cording to NASA scientists, the coating is especially promising as a technology to reduce
stray light, which can overwhelm faint signals that sensitive detectors are supposed to re-
trieve. Ground-based laboratory testing proves that the coating absorbs 99.5% of the light
in the ultraviolet and visible spectrum and 99.8% in the far-infrared bands. Instrument de-
velopers typically apply black paint on baffles and other instrument components to reduce
errant light, but these techniques absorb only 90-96% of the light, says principal investiga-
tor John Hagopian.
The new coating’s super-absorbency is based on the fact that the nanotubes are mostly
empty space. However, the carbon atoms absorb the light and prevent it from reflecting off
surfaces. Because only a tiny fraction of light reflects off the coating, sensitive detectors see
the material as extremely black. The experiment, comprised of two trays containing two ti-
tanium discs coated with carbon nanotubes as well as other coating samples, are included
on one of the new task boards for NASA’s Robotic Refueling Mission (RRM)-Phase 2, which
arrived at the ISS on August 12. Trays will be exposed to space for one year and then re-
turned to Goddard Space Flight Center, Greenbelt, Md., for evaluation.
The experiment will be exposed to harsh radiation and other elements, including
atomic oxygen that reacts with spacecraft materials and corrodes them. Determining
whether or not the coating can withstand ex-
treme environmental conditions will help fur-
ther qualify the technology for potential use on
space-based instruments. nasa.gov.
A new carbon-nanotube coating is one of several
materials being tested on the ISS as part of the
Materials Coating Experiment. The super-black
material occupies the “D” slot on the sample tray.
Courtesy of NASA/Bill Squicciarini.
ADVANCED MATERIALS & PROCESSES • OCTOBER 2014 15
SURFACE ENGINEERING
news
industry
briefs
LiquiGlide Inc., Cambridge,
Mass., initiated international
patent filings to
protect the
intellectual property (IP) of its
liquid-impregnated surface
technology. The international
patent filing is directly related to
U.S. Patent 8,574,704, granted to
Massachusetts Institute of
Technology (MIT), Cambridge. MIT
holds two patents for the slippery
coating technology with more than
a dozen pending and LiquiGlide is
the sole commercial entity with
exclusive licensing rights. The 704
patent was granted in November
2013 and describes the company’s
method for creating permanently
wet slippery surfaces by stably
trapping liquids in a matrix of
solid, micro-scale engineered
features, reducing friction for
viscous liquids moving across
treated surfaces. .
Aixtron SE, Germany, a
semiconductor deposition
equipment supplier, is working
with Fraunhofer IISB, Germany, to
develop 150 mm silicon carbide
(SiC) epitaxy processes using the
new Aixtron 8x150 mm G5WW
vapor phase epitaxy system. The
company’s Planetary Reactor tool
will be installed at the IISB
cleanroom laboratory later this
year. Fraunhofer has expertise in
low-defect-density SiC epitaxial
processes, critical for
manufacturing high-voltage SiC
devices. Special characterization
techniques such as room
temperature photoluminescence
imaging and selective defect
etching were developed and
adapted to SiC material properties
at its research facility. ,
.
A bead of water sitting on top of
water-resistant polymer crystals.
Courtesy of Kyoto University.