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Bouncing water creates efficient power
In a Brigham Young University lab, Provo, Utah, me-
chanical engineering professor Julie Crockett analyzes
water as it bounces like a ball and rolls down a ramp.
This phenomenon occurs because Crockett and her col-
league Dan Maynes created a sloped channel that is su-
perhydrophobic—extremely difficult to wet. “Our
research is geared toward helping to create the ideal su-
perhydrophobic surface,” says Crockett. “By character-
izing the specific properties of these different surfaces,
we can better pinpoint which types of surfaces are most
advantageous for each application.”
The superhydrophobic surfaces researchers are test-
ing in the lab fall into one of two categories—surfaces
with micro posts or surfaces with ribs and cavities one-
tenth the size of a human hair. To create these microstructured surfaces, a process similar
to photo film development that etches patterns onto CD-sized wafers was used. Re-
searchers then add a thin water-resistant film to the surfaces, such as Teflon, and use ultra-
high-speed cameras to document the way water interacts when dropped, jetted, or boiled
on them. Slight alterations in the width of the ribs and cavities, or the angles of the rib
walls, significantly change the water’s responses. For more information: Julie Crockett,
, .
Nanotrusses as future structural materials
An elaborate fractal structure is the latest example of what Julia Greer, professor of ma-
terials science and mechanics at California Institute of Technology, Pasadena, calls a fractal
nanotruss. Her group developed a three-step process for building such complex structures
very precisely. A direct laser writing method called two-
photon lithography is first used to “write” a 3D pattern in
a polymer, allowing a laser beam to crosslink and harden
the polymer wherever it is focused. At the end of the pat-
terning step, the parts of the polymer that were exposed
to the laser remain intact while the rest is dissolved away,
revealing a 3D scaffold. The polymer scaffold is then
coated with a continuous, very thin layer of a material,
which can be a ceramic, metal, metallic glass, semiconduc-
tor, or “just about anything,” Greer says. In this case, they
used alumina or aluminum oxide to coat the scaffold. In
the final step, they etch out the polymer from within the
structure, leaving a hollow architecture.
Taking advantage of some of the size effects that
many materials display at the nanoscale, these nanotrusses can have unusual, desirable
qualities. For example, intrinsically brittle materials, like ceramics, including the alumina
shown, can be made deformable so that they can be crushed and still rebound to their orig-
inal state without global failure. For more information: Julia Greer, 626.395.4127,
, .
Metco joins Oerlikon Group
The Oerlikon Group, Switzerland, acquired Metco from Sulzer AG ahead of schedule.
Oerlikon Balzers and Oerlikon Metco now form Oerlikon’s Surface Solutions Segment.
Oerlikon Balzers is a global technology leader in the PVD thin film business, while Oerlikon
Metco is involved in the thermal spray and surface applications business. Oerlikon Metco
officials say they plan to emulate Oerlikon Balzers’ service approach to further grow the
thermal spray service business.
ADVANCED MATERIALS & PROCESSES • SEPTEMBER 2014 15
SURFACE ENGINEERING
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Researchers from Isfahan
University of Technology, Iran,
produced biocompatible materials
based on a metallic alloy to modify
tissue engineering materials
properties. The nanostructure is
corrosion resistant and connects
well with bones. A combination of
nanostructured bilayer coatings
was used in production. In addition
to increasing corrosion resistance
in the substrate sample
(magnesium alloy), the method
improves connectivity of the
artificial implant with the bone.
Cells cannot tell the difference
between the bone and implant due
to the chemical similarity between
the surface of bioactive glass used
in the coating and the inorganic
section of the bone.
A new biocompatible
nanocoating resists corrosion
and connects well with bones.
Saint-Gobain, France, finalized
the acquisition of Phoenix
Coating Resources Inc.,
Mulberry, Fla. Phoenix
manufactures ceramic ingots used
to produce high-resistance
thermal coatings on metal parts
for the aeronautics industry. The
aim is to improve the energy
efficiency of aircraft engines by
enabling them to operate at higher
temperatures. The acquisition
allows Saint-Gobain to expand its
range of aerospace coatings.
.
Superhydrophobic surfaces
cause water to bead up like a
ball. Courtesy of Jaren Wilkey.
An elaborate fractal structure
could be used for structural
engineering materials. Courtesy
of L. Meza, et al., Caltech.