Author(s): Andrew Thomson, Tyler Peterson, Anna Jensen, Daniel Orr
Mentor(s): Anton Bowden
Institution BYU
INTRODUCTION: Our lab recently developed a 3D-printed titanium intervertebral implant intended to improve spinal surgery outcomes. However, friction on the implant’s bearing surfaces can generate microscopic wear debris, leading to potential complications. OBJECTIVE: We hypothesized that a smoother surface finish on the implant would reduce wear. The goal of this experiment was to create a container compatible with a planetary mixer to polish the implant's critical surfaces using high-speed abrasive fluid flow. METHODS: The container was designed like a small cup with a screw-on cap. The main considerations during development were the weight restriction (100g) and waterproofing requirements. To reduce weight, it was 3D printed with a wall thickness of 1mm. Porosity was minimized by using solid infill and a 0.1mm layer height, preventing fluid from escaping under the centrifugal force of the mixer. An O-ring was integrated into the lid to prevent fluid leakage through the threads. Instead of placing one device in the center, two devices were mounted along the inside perimeter of the container. This setup improved abrasive flow while maintaining balance. Aluminum oxide (Al₂O₃) was selected as the abrasive grit for its fine, acicular structure. Initially, a dilute Al₂O₃-water suspension was mixed for two minutes, followed by a second round using a higher Al₂O₃-to-water ratio. RESULTS: The final container weighed 99g and successfully retained fluid during 12-second high-speed mixing intervals. However, neither the dilute nor the viscous fluid caused a significant roughness change. The viscous mixture led to Al₂O₃ buildup on the bearing surfaces. DISCUSSION: The final container had several benefits, including successfully retaining fluid during testing and a lightweight design compatible with the planetary mixer’s capacity. Its design allowed efficient fluid mixing, demonstrating potential for short-duration polishing tests. However, the setup was unable to generate sufficient abrasive action to effectively polish the device’s surfaces. It is also unclear if the container can hold fluid indefinitely. CONCLUSION: While polishing titanium with abrasive liquid is possible, it is not reasonable to do so with the methods described. High-flow treatment requires more powerful abrasion to adequately polish 3D-printed titanium.