Harnessing radical new tools—from ultrafast laser imagers to groundbreaking chemical synthesis approaches—DARPA’s
Defense Sciences Office (DSO) is aggressively pursuing the development
of novel materials with the potential to boost national security.
One major challenge in developing new materials has been the
difficulty of retaining and exploiting the unique characteristics that
emerge in materials at the nanoscale (a few 10-billionths of a meter).
Many materials demonstrate unique and potentially useful electrical,
optical and tensile characteristics at these nearly atomic scales, but
lose these traits when engineered into millimeter- or centimeter-scale
products and systems. DSO’s Atoms to Product (A2P) program
aims to cross that divide by developing assembly methods that allow the
retention of desirable nanoscale properties in macro-scale materials,
components and systems.
“In the past, scientists made most of their new materials through
variants of ‘mix, heat and form,’” said DARPA program manager John Main.
“Now we’re taking an entirely different approach, starting with
individual atoms, assembling them into nano-structures, then assembling
the nano-structures into larger micro-devices. A2P is taking advantage
of new methods for controlling nanoscale assembly at very high
throughputs to economically build novel micro-devices.”
DARPA is pursuing other approaches to creating new materials
with unique properties through its Materials with Controlled
Microstructural Architecture (MCMA) program. This program seeks to
control the architecture of material microstructures to improve
structural efficiency and realize properties that traditionally aren’t
achieved together in a single substance, such as the strength of steel
and the weight of plastic. The work could also help incorporate other
important properties, such as high rates of heat diffusion for thermal
management applications and tailorability of thermal expansion to enable
joining of normally incompatible materials
One potential benefit of applying control over the internal,
nano-architecture of materials is that the materials may then be able
to catalyze reactions or perform energy conversions, effectively
becoming devices in and of themselves. That’s precisely the goal of
DSO’s Materials for Transduction (MATRIX) program. Like A2P, it aims to
realize the beneficial properties of new materials at the device or
system level—in this case by developing new materials for transduction,
the conversion of energy from one form into another.
“Transduction is critical to countless military capabilities on land,
under water, in the air and in space,” said DARPA program manager Jim
Gimlett, pointing to such examples as communications antennas, which
convert radio waves to electrical signals, and thermoelectric
generators, which convert heat to electricity. But research efforts to
develop new transductional materials have largely been limited to
laboratory demonstrations and have too often failed to translate into
functional devices and systems. MATRIX aims to make a difference by
speeding the development of significant new capabilities and enabling
size and weight reductions for existing military devices and systems.
DSO’s Extended Solids (XSolids)
program takes aim at a different class of materials—those that
currently can be made and exist only at ultrahigh pressures up to
millions of times atmospheric pressure. Many materials subjected to
these pressures exhibit dramatic improvements in their physical,
mechanical and functional properties. These new “polymorphs” may provide
significant performance enhancements in areas as diverse as
semiconductor electronics and propulsion, and in structural applications
ranging from aerospace to ground vehicles. “The discovery and
fabrication of new materials has long been based on the application of
heat,” said Goldwasser. “The development of high-pressure chemistry—or
barochemistry—could open up a new era in materials discovery and
development featuring an entirely new palette of materials for
exploitation.”
Early work already hints at unique materials and properties that may
emerge when everyday gasses such as carbon dioxide as well as silicon-
and carbon-based solids are compressed under extreme conditions,
Goldwasser noted. But because their synthesis and stabilization is so
demanding, production of these materials for practical use has proven
difficult. So in addition to materials discovery, XSolids is researching
processing techniques to make their fabrication practical.
Recent scientific advances have opened up new possibilities for material
design in the ultrahigh pressure regime (up to three million times
higher than atmospheric pressure). Materials formed under ultrahigh
pressure, known as extended solids, exhibit dramatic changes in
physical, mechanical and functional properties and may offer significant
improvements to armor, electronics, propulsion and munitions systems in
any aerospace, ground or naval platform.
Despite the dramatic performance improvements—both demonstrated and
predicted—for extended solids, the ultrahigh pressures currently
required for synthesis and stabilization of such materials prevent
scalability for any practical use. DARPA created the Extended Solids
(XSolids) program to address the key challenges in synthesis and
scale-up necessary for manufacture, through both computational and
experimental approaches, with the intention of opening a vast new
material design space for the DoD.
Interdisciplinary research teams are working to develop multi-step,
barochemical processes that can reduce the peak pressure needed to
achieve scalable synthesis of target materials. Performers are working
in parallel on computational exploration of high-pressure material
structures and properties, and the small-scale synthesis of a variety of
materials to experimentally verify their properties.
While A2P, MATRIX and XSolids all address in various ways the challenge
of scaling innovations from smaller to larger dimensions, another DSO
materials program is addressing the challenge of how to add precision to
the production of extremely thin films of substances. DSO’s Local
Control of Materials Synthesis (LoCo) program seeks to advance thin-film
materials and surface coatings, which are used in military applications
ranging from optics to advanced electronics.
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