Historical research guide · 0077 · 2010
DIRD Biomaterials
DIA / AAWSAP contractor
In one minute
This is the odd one out among the thirty-eight Defense Intelligence Reference Documents, and worth reading for exactly that reason. It is a straight materials-science review of biomaterials — the metals, ceramics, polymers, glasses and carbons that are made to interface with living tissue — written for the same programme that commissioned the warp drive, wormhole and aneutronic fusion papers. The author walks through silicone, Teflon, biodegradable polylactide and polyglycolide, hydrogels, titanium, bioceramics and cultured tissue constructs, and then through where they are used: heart valves, vascular grafts, stents, hip and knee joints, contact lenses, drug delivery and kidney dialysis. The recurring theme is that the body fights back. Proteins and cells foul any surface you implant, and the report’s closing judgement is that implant materials are still essentially the ones available twenty years earlier, because life-and-death materials are slow and expensive to qualify.
Connection
Chapter 1 makes the case that the DIRD list is an engineering reading list rather than a collection of exotica, and this report is the cleanest evidence of that: the same programme paid for ordinary, rigorous materials science alongside the metric engineering. It also states the constraint the rest of the library keeps running into — that the bottleneck on a new capability is usually the material, and qualifying a material takes money and years.
From the source
Existing materials for implants are generally based on materials that have been available for more than 20 years; most of the innovation is occurring in devising new ways to embody the materials and apply them to new applications, because materials serving life-and-death functions require large amounts of money and time to test rigorously.Summary and Recommendations, p. 25
Biocompatibility, not sensitivity, is the limit on implanted sensors: biofouling coats the sensing interface with proteins, blood-formed elements, adherent immunological cells and scar tissue, and in more than 600 reported studies since 1996 the results were poor enough that many companies abandoned implantable sensor devices altogether and moved to sensors placed outside the body.Introduction, Importance of Biocompatibility, p. vii; Biomaterials for Biosensors, pp. 1-2
Titanium integrates with living bone. Per-Ingvar Brånemark found in 1952 that rabbit bone fixed in a roughly machined titanium holder had integrated so completely that removing it was impossible — he named this osseointegration — and the thin, hard, inert titania layer that forms on exposure to air is thought to be largely responsible for titanium’s acceptability where metal corrosion in warm, salty body fluids would ordinarily be a problem.Medical Titanium as a Biomaterial, pp. 22-23
Nitinol stents work by a solid-state phase change rather than a mechanism: the shape memory alloy is held collapsed and cold by a flow of refrigerated saline through the catheter, and on warming to body temperature it expands itself and applies a calibrated pressure to the vessel wall more reproducibly than a balloon can.Stent Biomaterials and Nitinol as a Biomaterial, pp. 18-19
Degradation time is a design parameter: combining short-lived polylactide with longer-lived polyglycolide produces polymers with intermediate decomposition times, so a fixation system can be engineered to degrade at a rate that slowly transfers load to the healing bone, avoiding the refracture that follows removal of a rigid stainless implant and eliminating the second surgery.Degradable Biomaterials, p. 8; Biodegradation Advantages, p. 8
The open problem in tissue engineering is blood supply: scaffold-grown structures do not create their own networks of blood vessels, and without angiogenesis inside the scaffold construct in a timely fashion the cells die and mass infection occurs — a problem whose solution lies in the future.Tissue Constructs as Biomaterials, p. 14; Tissue Scaffold Biomaterials, pp. 14-15
The way in
https://documents2.theblackvault.com/documents/dia/AAWSAP-DIRDs/DIRD_04_DIRD_Biomaterials.pdfHow to cite it
DIA / AAWSAP contractor (2010) DIRD Biomaterials https://documents2.theblackvault.com/documents/dia/AAWSAP-DIRDs/DIRD_04_DIRD_Biomaterials.pdf