University Honors

A brain aneurysm is a bulging artery inside the brain that can rupture, often causing severe debilitation or death. A potential patient-specific treatment involves using a polyurethane shape memory polymer (SMP)-based foam that can be compressed for endovascular surgical insertion and then expanded with heat to maximally fill the aneurysm space. By blocking blood flow into the aneurysm, the customizable SMPs reduce rupture risk and improve patient outcomes. However, their long-term mechanical durability and shape recovery capabilities must be well understood before they can be safely implemented in medical applications. The goal of this research is to examine the durability, shape retention, and recovery time of SMPs through repeated compression tests, so this material can eventually be used to treat patients. A total of 18 SMP foams were fabricated with 10%, 15%, and 20% infill densities using fixed ratios of three monomers: (i) hexamethylene diisocyanate (HDI), (ii) N,N,N0,N0-tetrakis (hydroxypropyl) ethylenediamine (HPED), and (iii) triethanolamine (TEA). Nine samples underwent 15 cycles of compression tests at 60 ∞C to characterize the materialís stress-strain behavior, with recovery time recorded by a camera, and microscope images taken every five cycles to assess any structural changes or damage. The remaining nine samples underwent 10 cycles of compression at 60 ∞C, followed by another 10 cycles of compression at room temperature (~20 ∞C). The stress-strain results were compared across infill densities and recovery levels to determine how repeated compression influences the SMPsí thermo-mechanical properties. This research showed that repeated compression cycles caused reduced stress, structural changes in overall morphology, and variations in recovery time. The SMP foam cubes were able to withstand the repeated compression cycles and retain their functionality, showing promise in their application in future medical applications.