PhD Thesis Proposal: Peder Solberg

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Meeting ID: 996 1313 1415
Passcode: 009838

"Application-Driven Materials Development of Solid-State Conductive Composites of Ultra-High Molecular Weight Polyethylene"

Abstract

Ultra-high molecular weight polyethylene (UHMWPE) is a linear long chain homopolymer valued for its toughness, wear resistance, and chemical inertness. In the medical field, these properties make it the material of choice for bearing surfaces despite recognized tradeoffs between wear resistance, toughness, and oxidation resistance. To avoid these tradeoffs, UHMWPE composites have been studied in orthopedic research for decades. Several solid-state composite products have been released, with recent instances (e.g., antioxidant UHMWPE bearings) showing more clinical success than early ones (e.g., carbon fiber reinforced UHMWPE bearings). No clinical applications of conductive composite UHMWPE have been cleared for use, though the future of personalized medicine suggests patients might benefit from such materials if other beneficial properties can be maintained.

Clinical need-finding conducted over the past two academic years through Dartmouth's Training Program in Surgical Innovation revealed several potential applications for conductive, load-bearing polymers. These include:

1. conductive knee bearings for electrochemical treatment of prosthetic joint infection,
2. strain sensors for arthroplasty and spinal applications, and
3. electrodes for embedded sensors in orthopedic bearings.

Each application area demands specific material properties, requiring a framework for producing a tough, conductive polymer composite with adjustable parameters while considering property tradeoffs.

The overall objective for this work is to illuminate the structure-property relationships present in solid-state composites of UHMWPE, doing so in a way that also answers practical questions regarding the viability of these materials for clinical applications.

Carbon nanoparticles are proposed here as an additive that can be integrated into UHMWPE to confer conductive properties while providing good interphase adhesion. Preliminary data suggests that concentrations conferring conductive properties lead to diminished mechanical properties due to increased presence of the additive. Moreover, decreases in toughness as defined through tensile, impact, and fatigue measures are not necessarily correlated with each other. Thus, tradeoffs between electrical and mechanical properties must be described and fundamentally understood at the micro- and meso-scales for these materials to be engineered for specific high-load electrical applications. More broadly, the results will be generalizable to expand our knowledge base of these segregated network conductive polymer composites.

Thesis Committee

• Prof. Douglas Van Citters, Chair
• Prof. John X.J. Zhang
• Prof. Ian Baker
• Prof. Igor Tsukrov (UNH)

Contact

For more information, contact Julia Abraham at julia.s.abraham@dartmouth.edu.