SUBJECT: Ph.D. Proposal Presentation
BY: Andrew Miller
TIME: Thursday, April 21, 2016, 11:00 a.m.
PLACE: ES&T, 1229
TITLE: Fatigue and Cyclic Loading of 3D Printed Soft Polymers for Orthopedic Applications
COMMITTEE: Dr. Robert E. Guldberg, Co-Chair (BioE, ME)
Dr. Ken Gall, Co-Chair (MEMS (Duke))
Dr. Johnna S. Temenoff (BME)
Dr. Nick Willett (BioE)
Dr. Meisha L. Shofner (MSE)


The use of soft materials in orthopedic applications has largely been stalled due to a lack of biocompatible materials with sufficient fatigue resistance. Silicone was once touted as a potentially suitable material for the replacement of arthritic joints, however numerous studies since have documented cases of failed implants when silicone is used in hand, foot, wrist, and spinal applications. The failure of these implants is generally attributed to fracture, compressive deformation, and wear leading to inflammation, arthritis, foreign body response, and loss of function. More recently there has been a large push for polyurethanes in soft orthopedic devices, specifically polycarbonate urethane (PCU). PCU has been used in applications such as intervertebral disc replacements, acetabular cup bearing surfaces, and meniscal implants, among others. Early clinical data for these devices is promising, with some already in use overseas or in US clinical trials. However, a literature search turns up a surprising lack of fundamental knowledge pertaining to the fatigue and cyclic loading response of PCU. In a more general sense, the relationships between soft polymer structure/processing and fatigue performance are largely understudied.

With the studies proposed, we hope to provide fundamental knowledge as to the relationships between soft polymer structure and processing and fatigue performance. We will start by investigating relationships between soft polymer structure and compressive fatigue performance for an array of soft synthetic polymers, which we will compare to native soft tissue. From there, we will focus our efforts on polycarbonate urethane (PCU), which has recently shown great promise in vivo. Studies on PCU will include examining the effects of hard segment content as well as 3D printing, and a 3D printed topography, on the resulting fatigue properties. Such studies will provide fundamental knowledge useful for the use and optimization of soft polymers in fatigue prone applications.