A flow loop test was performed using a 3D printed version of the final venous stent design and porcine blood. As hoped, the stent did not migrate during the test.
In addition, stainless steel was found to be a hemocompatible material when compared to positive and negative controls.
The venous stent team is happy to report that they have won the outstanding undergraduate design award at the 2017 Northeast Biomedical Engineering Conference, earning third place in the design competition. The link to their presentation can be found below.
NEBEC Presentation – Venous Stent
Over the past couple of months, the team has been working to optimize the venous stent design. To accomplish this, ANSYS was used to perform flow and mechanical tests that were used to optimize every aspect of the stent.
ANSYS Fluent Flow Testing
ANSYS Static Structural Compression Testing
Results from these tests were analyzed using a scoring method the team developed. Parameters that were optimized include:
- Ring Shape
- Ring Height
- Connection Shape
- Connection Length
- Number of Connections
- Strut Thickness
- Strut Width
Finally, the team was able to determine the following design is optimized for use in treating May-Thurner Syndrome.
An updated timeline for the Stent Team:
Finalize Simulation Testing Protocol by February 1
- Flow, pinching and hoop stress verification protocols
- Determine appropriate parameters/initial conditions
- Determine and justify whether or not to use the actual curved vessel, deformable wall, or simplified model
Develop Mechanical Testing Protocol and Order Parts by February 17
- Flow loop – tubing, connectors, peristaltic pump, blood/blood substitute
- Instron – 3d printed spine(?), tubing, attachments
Optimize Stent by March 10
- Create various stents altering strut shape, thickness, width, connections, spacing
- Test to meet specifications using the developed protocols
Finish Printing by March 17
Finish Physical Testing by April 21
At the end of the Fall 2016 Semester, the Stent team developed the following overall design solution for their venous stent for May-Thurner Syndrome.
Material: Stainless Steel
Overall Geometry: Open Cell, Varying diameters specific for iliac vein
Ring Shape: Sinusoidal
Number of Ring Connections: Vary by proximity to compression
Flexibility: Open cell, minimal connections
Surface Area/Strut Width: Optimize for radial strength and to avoid endothelial damage
Here are the requirements for our stent:
- The device must have a radial resistive force to maintain patency and resist the force applied by the iliac artery.
- The device must maintain proper fluid flow dynamics.
- The device on the vessel wall must keep the endothelium intact.
- The device must maintain a clinically relevant placement in the body after deployment.
- The product line must be available in discrete sizes to meet surgical need.
- The device must be hemocompatible.
- The device must be able to resist corrosion in the body.
- The device must be visible under fluroscopy during delivery.
- The device must be compatible with current surgical technique.
The first month of the semester for senior design has been spent developing design requirements, constraints and justifications. Current requirement focuses include fluid dynamics, impact on the endothelium, strength, sizing and material selection. Justifications and constraints for each requirement have been developed using scientific literature and appropriate engineering equations when necessary.
Directions for the next few weeks include developing a timeline, budget and testing parameters around the design requirements.