Radiopaque Marker Rivet Locking for Bioresorbable Scaffold Struts
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Solution Overview
Problem
Bioresorbable polymer scaffolds face challenges in securely attaching radiopaque markers due to significant plastic deformation during crimping and balloon expansion, leading to potential dislodgment and reduced reliability of marker attachment.
Innovation Solution
The use of reshaped markers and re-shaped holes, combined with a cold-forming process to create rivet-shaped markers and secure them in a trapezoidal or frustoconical shank, enhances marker retention and resistance to dislodgment, while maintaining a low profile to reduce thrombogenicity and improve manufacturing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional marker attachment methods are used on bioresorbable scaffolds, then the scaffolds can be delivered and deployed, but the markers become dislodged due to plastic deformation during crimping and balloon expansion
Solution Approach 1:
The marker is pre-formed with a rivet shape including a head and shank before attachment to the scaffold. The shank is inserted into a hole in the scaffold strut, and then the shank is deformed (swaged) to create a frustoconical or trapezoidal shape that mechanically locks the marker in place. This preliminary formation of the rivet structure enables the marker to withstand subsequent plastic deformation during crimping and balloon expansion without dislodging.
2Reliability
If markers are securely attached to scaffold struts, then marker retention is improved, but the profile of the scaffold increases which may increase thrombogenicity
Solution Approach 1:
The scaffold strut is designed with a localized hole and surrounding structure specifically at the marker attachment site. The hole has a specific diameter and the surrounding strut material is configured to accommodate the rivet shank deformation. This localized structural modification provides secure marker retention while minimizing the overall profile increase of the scaffold, as only the specific attachment regions are modified rather than the entire scaffold structure.
3Ease of manufacture
If manual marker attachment methods are used, then attachment can be performed, but manufacturing efficiency is reduced and costs increase
Solution Approach 1:
The rivet-shaped marker is designed to be self-retaining through its own structural features. The shank is inserted into the hole and then deformed using a swaging tool that compresses the shank material radially outward, creating a frustoconical or trapezoidal shape that mechanically locks into the hole. This self-locking mechanism eliminates the need for separate adhesive applications, heat treatment steps, or complex assembly procedures, enabling automated high-speed manufacturing.
4Strength
If the rivet shank is deformed to create a frustoconical or trapezoidal shape, then resistance to push-out forces is increased, but the attachment process becomes more complex
Solution Approach 1:
The mechanical deformation process (swaging) that creates the frustoconical or trapezoidal shank shape replaces the need for chemical adhesives, heat treatment, or multi-step mechanical assembly. A single swaging action using a controlled compression force radially deforms the metallic shank material to create the locking geometry. This mechanical substitution simplifies the overall process by consolidating multiple potential steps into one efficient deformation operation.
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
This approach ensures reliable attachment and retention of radiopaque markers on bioresorbable scaffolds, reducing the risk of thrombosis and improving manufacturing costs by automating the rivet installation process and enhancing the scaffold's resistance to dislodgment forces.
Implementation Method 1
A method for making a medical device includes cold-forming, with a die, a spherical bead into a rivet having a head and shank
Implementation Method 2
The rivet marker is secured in the hole by deforming the shank to thereby create a frustoconical or trapezoidal shaped deformed shank that resists push-out forces
Implementation Method 3
an interference fit between the rivet and the hole
Data Source
AI summary
A scaffold includes a radiopaque marker connected to a strut. The marker is retained within the strut by a head at one or both ends. The marker is attached to the strut by a process that includes forming a rivet from a radiopaque bead and attaching the rivet to the marker including deforming the rivet to enhance resistance to dislodgement during crimping or balloon expansion. The strut has a thickness of about 100 microns.