Book excerpt: Abstract: Nanotechnology is continually becoming more integrated into consumer products used by the general public on a daily basis. Consumers reap the benefits of enhanced properties for these commercial products, and yet they are still affordable. For biomedical products, that include nanofeatures, this is not yet a reality. The materials and methods used to fabricate these products are still far too expensive. There are many inexpensive and commercially available polymers that have potential to be used in these advanced biomedical products, but the fabrication techniques still lack the simplicity required to create an inexpensive end product. Supercritical CO2 has been used to overcome the polymeric nanofabrication barriers for high throughput production of biomedical devices. Novel CO2-assisted low temperature polymer nanoprocessing fabrication techniques have been implemented for use in biomedical product creation. Polymer nanofabrication techniques such as bonding, imprinting, and active biomolecule immobilization were demonstrated. Due to being CO2-assisted techniques, these processes are intrinsically inexpensive and environmentally benign. In order to thoroughly investigate these nanofabrication techniques the interactions between CO2 and the polymer were examined on a thermodynamic level. Thermodynamic modeling results of high pressure CO2/polystyrene systems were used along with experimental bonding, imprinting, and immobilization results. It was found that the solubility of CO2 in a polymer matrix and the resulting reduction of the polymer glass transition temperature (Tg) largely dictate the polymer chain mobility and therefore the polymer's processability. For instance, it was shown that the polymer bond strength of polystyrene, bonded via a CO2-assisted technique, depended largely on the proximity of the processing conditions to the reduced Tg curve. It was also found that low aspect ratio nanofeatures could be patterned by CO2-assisted nanoimprint lithography in polystyrene at conditions near the reduced Tg curve. These CO2-assisted low temperature polymer processing techniques are now better understood in terms of the CO2/polymer thermodynamic properties, thus making these, and other similar, techniques easier to control. This fundamental information can be applied to scaling-up these technologies so that inexpensive polymer biomedical products with nanofeatures can soon be commercially produced, thus benefiting the health of society.