AAWSAP DIRD, Biomaterials, January 2010

This Defense Intelligence Reference Document, dated 7 January 2010, was prepared by the Defense Intelligence Agency's Defense Warning Office. It is one of a series of advanced technology reports produced in FY 2009 under the Advanced Aerospace Weapon System Applications program. The report reviews biomaterials used in medicine, including silicones, Teflon, biodegradable polymers, hydrogels, titanium, ceramics and tissue constructs, and applications such as stents, joints, contact lenses, drug delivery and dialysis. It concludes that most innovation lies in new ways to apply existing materials.

From the source:Release of 2026-09-18 Incident: 1/7/10, Las Vegas, Nevada. Released with redactions. This document is a Defense Intelligence Reference Document (DIRD), a technical reference format used by the Defense Intelligence Agency (DIA) to capture baseline knowledge on a specific topic for later analytic use. DIRDs are best understood as reference and synthesis products rather than as original research. It is one of 38 DIRDs produced under the Advanced Aerospace Weapon System Applications Program (AAWSAP) between 2009 and 2011. Because AAWSAP’s scope permitted a broad range of supporting topics, not every DIRD in the series directly concerns aerospace systems or future threat assessment. The following summary reflects the DIRD’s scope and framing at the time of writing and should not be read as implying current validation of the concepts discussed. This DIRD is a broad survey of biomaterials, including metals, polymers, ceramics, glasses, and composites designed to interact with living tissue, and argues that their value depends mainly on biocompatibility, reliability, and careful matching of material properties to specific medical uses. The report reviews major application areas including biosensors, implants, cardiovascular devices, contact lenses, drug delivery systems, tissue constructs, titanium devices, and dialysis membranes, emphasizing that no single biomaterial works best in every setting. Its overall conclusion is that biomaterials are already foundational to a large medical-device industry and save or improve millions of lives, but that progress tends to be slow because safety testing is stringent; as a result, most advances come from improved ways of applying established materials such as silicone, Teflon, biodegradable polymers, ceramics, and titanium in new devices and clinical settings rather than from radically new substances.

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NITINOL AS A BIOMATERIAL
The use of nitinol metal in stents is a clever application of the properties of a class of
materials called shape memory alloys (SMAs). SMAs are mixtures of metals that, after
being stress treated, can be deformed significantly but then triggered to return to their
original shape.
SMAs have a rather remarkable
property: they remember their shape.
This " smart" property is the result of
the substance's ability to undergo a
phase change . This occurs at the
atom ic level, where atoms in the solid
subtly sh ift their positions in response
to a stimulus, such as a change in
temperature or the app lication of
mechanical stress.
Once the metal is formed at a high
temperature it remembers th is shape.
Subsequent distortions of the material
when it is cold remain locked in place
while the material remains at a low
temperatu re. However, warming the
material to a specific temperature that
is relatively closer to its formation
temperatu re will trigger a return to its
original formed shape .
In stents, the web is collapsed while it
is cold for easy insertion into a blood
vessel and held cold by a flow of cold
saline out of the catheter. When the
stent warms up as the catheter is Figure 26. Nitinol Stent. Nit inol is an alloy of tita nium. It
removed, it expands itself and the is biocompatible and also a shape memory material.
surround ing blood vessel. Figure 26
shows a Nitinol stent.
CONTACT LENSES
Contact lenses are used to correct vision in the same way as worn glasses but are
lightweight and virtually invisible. Their practica lity and popularity ultimately depend on
the biomaterials of which they are made.
Modern soft contact lenses were invented by Czech chem ist Otto Wichterle and his
assistant, Drahoslav Um who also invented the first gel used for their production.
However, it was not until the employment of poly-methyl -methacry late, known as
PMMA (a cousin of acrylic plastics, such as Plexiglas™), that they began to enjoy mass
appeal. Figure 27 shows a gas-permeable contact lens.
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