AAWSAP DIRD, Biomaterials, January 2010

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UNCLASSIFIED/;'FOR OFFI@IAL YSE OHL¥
SILICONE CHEMISTRY
Silicone is actually a common name
for the chemical compound
polydimethylsiloxane (PDMS), a class
of synthetic polymers with repeating
units of silicon and oxygen. Figure 5
shows the polymeric repeating
structure of medical silicones. Various
functional groups-often methyl-can
be attached to that backbone to
change the material properties.
Silicone polymers can easily be
transformed into linear or cross­
linking materials without using any
toxic plasticizers. The resulting
materials are elastic at body
temperature.
The simultaneous presence of
Figures. Silicone Chemical Groups
different groups attached to the
silicon-oxygen backbone gives silicones a range of viscous and mechanical properties
that allow their use as fluids, emulsions, compounds, resins, and elastomers in
numerous applications. Thus, silicone is a versatile polymer, although its use is often
limited by its relatively poor mechanical strength. However, this limitation can be
overcome by reinforcing silicone with a silica filler or by chemically modifying the
backbone.
The stability, lack of toxicity, and excellent biocompatibility of PDMS make these
materials well suited for use in personal care, pharmaceutical, and medical device
applications. Silicone is easily molded and cast using room temperature curing (known
as RTV) or through the use of an organic catalyst.
SILICONE IN BIOMEDICAL PRODUCTS
Silicone membranes are made by casting the silicone liquid precursor into thin sheets.
Such membranes are often used in oxygen and carbon dioxide blood biosensors
because membranes made of this material are highly transmissive to these gases while
they block most other chemical substances present in the blood stream. In addition,
silicone's resistance to protein adhesion and its excellent overall biocompatibility make
it one of the most commonly used materials for encapsulating biosensors for tissue or
blood contact.
Recent formulations of silicone can be patterned with ultraviolet light and, thus, lend
themselves to manufacture with biosensors made by photolithography.
UNCLASSIFIED/ /EOR OFFICilAk YSE 8HLY
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