Material Selection

The material selection has proven to be the most important aspect of the design as the wrong material can lead to the failure of the device. Above all, the selected material must not fracture upon any form of loading, through any form of fracture mechanics. This constraint was studied through finite element analysis using SolidWorks Simulation. Additionally, as the clip is intended to be placed inside the human esophagus for prolonged periods, the materials should have undergone and passed previous biocompatibility tests.

To satisfy these constraints, the Granta EduPack: Level 3 Bioengineering Database developed by Ansys Incorporated, an engineering simulation software company, has been used for material selection. With the help from Ansys staff Bridget Ogwezi and Lakshana Mohee, the team was able to narrow down the material options based on mechanical properties, biocompatibility and cost aspects.

Limitations

Limited by Mechanical Properties and Biocompatibility

  • Based on USP Class VI and ISO 10993, all materials listed on the table and appendix are of medical grade.

  • In order to attach the clip to the tube easily and, we intend to have a material with relatively high Young’s modulus and yield strength so that the clip teeth could be open to 0.5 mm without fracture and able to undertake the rebound force from the tube.

  • Based on this consideration, PMMA that we currently use, satisfied the requirements - but PEEK would be a more optimal choice. PET, another commonly used medical material, was also expected to have similar mechanical performance to PMMA.

Limited by Cost ($/kg)

  • Since the goal is for mass production, the cost of material is also an important consideration as we want to reduce material costs as much as possible.

  • The price of PEEK per kg is almost 50 times higher than the price of PMMA per kg, but the cost for PET is even lower than the cost of acrylic.

  • The team determined the use of PMMA to be the optimal selection. Because the weight of each clip is approximately 2 grams, it is reasonably estimated that about 1 kilogram of material can produce around 400 to 500 clips at a material cost per clip of around $0.04-0.05.

  • Due to the limitation of 3D printable prototypes, the team is currently unable to test the performance of PET and PEEK materials, but we expected to manufacture the clip through injection molding eventually which PEEK and PET would be a valid options for further analysis.

Potential Material List




Full Potential Material List and TOP 10 Material List