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Figure 3.8 Cross section and longitudinal section of an inorganic fullerene-line nanoparticle
with an onionskin structural pattern (source: ApNano Materials and Tenne/Weizman Institute of
Science)
One of the most promising research directions for the development of active personal
protective systems is the “Liquid Armour” concept based on shear thickening fluids (STF)
or magnetorheological fluids. Liquid armour technology using shear thickening fluid is
being developed at the US Army Research Laboratory. The STF of this new protective
system is made up of hard silica nanoparticles suspended in polyethylene glycol, a nontoxic
fluid which can withstand a wide range of temperatures. To make liquid armour, the
STF is soaked into every layer of a standard Kevlar vest. The saturated fabric can be
soaked, draped, and sewn just like any other fabric. During normal handling, the STF in
the vest is very deformable and flows like a liquid. However, once a bullet or other
splinters or projectiles hits the vest, it transforms into a rigid material, which prevents
the projectile from penetrating the body.
At the Massachusetts Institute of Technology (MIT), the Institute for Soldier
Nanotechnologies has been working on a form of liquid armour that uses
magnetorheological fluids to produce new protective uniforms or armour vests for the US
Army. The nanofluids consist of iron nanoparticles suspended in a thick oil or syrup.
When a magnetic field is applied, the iron nanoparticles align and the fluid becomes
extremely stiff (see Figure 3.9). The degree of stiffness varies depending on the strength
of the applied field. The change happens extremely quickly — in about 20 milliseconds —
and the research team hopes that eventually, the fabric-fluid combination could resist
even a shockwave or shrapnel. The researchers at the MIT emphasize that their so-called
"instant armour" system needs another five to ten years of research before this material
is truly bullet-resistant and can be applied in personal protective systems for soldiers or
rescue forces and in other civil security systems.
Figure 3.9 Oily fluid full of tiny iron particles before being near a magnet (left); and after
(right) (source: Massachusetts Institute of Technology (MIT), Institute for Soldier
Nanotechnologies)
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