Project Overview: Testing and Modeling of Biocompatible Polymers

From the multi-color keys found on computer keyboards to complex engine components in modern cars, polymers offer an astoundingly broad range of optical, mechanical, thermal and chemical properties.  The ability to further tailor these properties during synthesis or through the use of additives has enabled remarkable advances in product innovation, manufacturing, service life, and the recyclability of polymeric products.  Another valuable characteristic of some polymers is biocompatibility, which refers to a polymer’s ability to contact or exist in a living system without causing harm or being rejected.  This attribute of certain polymers has enabled the creation of myriad medical devices directly responsible for improvements in patient care, recovery and quality of life.

One of the most enduring and successful examples of polymer based surgical treatment of a high occurrence and often debilitating medical condition can be seen in the case of joint disease or sever joint injury.  Pioneered in the late ’50s, total hip replacement through the use of a polymeric cup to assume the role of natural cartilage material ushered in the development of prosthetic joints with increasingly longer service lives and more natural ranges of motion.  Favorable wear and mechanical properties of non-biodegradable and biocompatible polymers such as ultrahigh molecular weight polyethylene (UHMWPE) naturally lie at the core of validating their use in total knee and hip replacement joints.  Conversely, in situations requiring greater matching of properties to those of muscle tissue and blood vessels, a softer and more elastic polymer (elastomer) is required.

In order to introduce methods of characterization and modeling applicable to biocompatible polymers, experimental data from UHMWPE, a relatively stiff and wear resistant polymer, and a polyurethane elastomer, a soft and elastic material, has been collected.  The experimental program included strain rate sensitivity, creep, relaxation and dynamics loading test protocols.  This data will be used to test the validity of various rheological models capable of simulating the visco-elastic behavior of various polymers.  The mathematical formulations of these models and the use of Matlab GUIs to create interactive environments are presented on this website.