Braided Stent Coating Uniformity via Pre-Stretching
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Solution Overview
Problem
Current methods for manufacturing medical devices, such as stents, fail to achieve an even coating distribution without imperfections like lumps, fibers, or webs, which can lead to thrombosis and other complications in treating aneurysms.
Innovation Solution
A heat-treated stent with a braided structure is coated using a process that maintains the device in a longitudinally stretched configuration during coating, ensuring a uniform and imperfection-free coating, utilizing a cantilevered fixture and air knifing to remove excess solution, and employing anti-thrombogenic materials like 2-Methacryloyloxyethyl phosphorylcholine (MPC) for reduced thrombogenicity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a coating is applied to a braided stent using conventional methods, then the stent receives a coating, but the coating contains imperfections such as lumps, fibers, and webs that obstruct pores
Solution Approach 1:
The stent is pre-stretched to its final expanded configuration before coating application. This preliminary action maintains the braided structure in an open, stable state during coating, preventing coating material from pooling between filaments and forming webs or lumps, thereby achieving a uniform coating without imperfections
Solution Approach 2:
The patent changes the physical state and geometry of the stent by stretching it to its expanded configuration during the coating process. This parameter change ensures that the pores remain open and the surface geometry is stable, allowing uniform coating deposition without the formation of obstructive imperfections
2Manufacturing precision
If the stent is stretched during coating to achieve uniform coating, then coating evenness improves, but the device complexity increases
Solution Approach 1:
The stent's braided structure serves multiple functions: it provides the mechanical scaffold for the device and simultaneously acts as the substrate that, when stretched, creates the optimal geometry for uniform coating application. The stretching mechanism integrates structure preparation and coating optimization into a single process step
3Reliability
If conventional coating materials are used, then the stent is coated, but thrombin formation occurs rapidly leading to thrombosis
Solution Approach 1:
The patent changes the chemical composition and surface properties of the coating material by using anti-thrombogenic substances such as heparin, hirudin, or endothelial cell growth factor. This parameter change in material composition fundamentally alters the biological interaction, preventing thrombin formation and reducing thrombogenicity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution results in a stent with a uniform, imperfection-free coating that significantly reduces thrombogenicity, delaying peak thrombin formation and enhancing the safety and efficacy of aneurysm treatment by minimizing the risk of clot formation.
Implementation Method 1
a coating material distributed over the filaments to form a coated flow diverting section
Implementation Method 2
utilizing a cantilevered fixture and air knifing to remove excess solution
Implementation Method 3
A heat-treated stent with a braided structure is coated
Data Source
AI summary
Medical devices that include a tubular member with a plurality of braided filaments, each filament crossing another of the filaments at a respective crossing point forming sidewall and a plurality of pores in the sidewall that are sized to inhibit flow of blood through the sidewall into an aneurysm to a degree sufficient to lead to thrombosis and healing of the aneurysm when the tubular member is positioned in a blood vessel and adjacent to the aneurysm, the pores have an average pore size that is less than or equal to about 500 microns when the tubular member is in an expanded state, the filaments possessing antithrombogenic surfaces to increase antithrombogenicity of the medical device with pores substantially free of webs formed by antithrombogenic material, such that fewer than 5% of the crossing points have webs formed by antithrombogenic material thereby permitting the pores to be substantially free of webs.