Bioabsorbable Stent U-Shaped Cell Stress Distribution
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Solution Overview
Problem
Conventional stents face challenges in achieving sufficient bending durability, expandability, and resistance to breakage when made from bioabsorbable metals with lower mechanical strength, often resulting in local corrosion and loss of physical properties.
Innovation Solution
A bioabsorbable stent design featuring a tubular structure with U-shaped cells and alternating tubular units, where the ratio of cell line widths and heights are optimized to distribute stress uniformly, and curved connecting parts are used to connect linear parts, preventing stress concentration and ensuring good adhesion and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If a bioabsorbable metal with lower mechanical strength is used to make the stent, then the stent can be degraded in the living body after completing its function, but the stent has insufficient strength and durability against bending loads
Solution Approach 1:
The stent is divided into multiple cells with U-shaped structures that have substantially linear parts and substantially circular arc parts. This segmentation allows stress to be distributed across multiple structural elements rather than concentrated in one location, improving overall strength while maintaining bioabsorbability.
Solution Approach 2:
The stent combines different geometric configurations (linear parts and circular arc parts) within a single bioabsorbable metal structure. This composite geometric design creates regions of different stiffness that work together to enhance overall mechanical strength and bending durability.
2Reliability
If the stent is designed with coupling parts to improve bending durability, then the stent has better resistance to repeated bending loads, but the stent becomes less expandable due to higher standard distension pressure required
Solution Approach 1:
The stent features localized circular arc parts with specific radius of curvature that are strategically positioned to provide flexibility where needed while maintaining structural integrity. The linear parts provide rigidity in regions requiring strength, creating local quality variations that balance expandability and bending durability.
3Device complexity
If coupling parts are located at the top of circular arc parts of opposing cells, then the stent structure is simplified, but stress concentrates at these locations causing insufficient durability and poor resistance to breakage
Solution Approach 1:
The stent incorporates substantially circular arc parts with optimized radius of curvature that naturally distribute stress through curved geometry. The curvature is designed to redirect stress away from concentration points, and coupling parts are positioned to connect these curved regions in a manner that maintains stress distribution, preventing breakage while keeping the structure relatively simple.
4Ease of operation
If the stent has high flexibility to pass through winding and narrow arteries, then the stent can be delivered to the lesion part, but the stent has insufficient radial force to support the artery wall
Solution Approach 1:
The stent design incorporates cells with specific height-to-width ratios and circular arc parts with optimized radius of curvature. These geometric parameters are carefully selected to provide the right balance: the curved parts enable flexibility for navigation through arteries, while the overall cell geometry and arrangement generate sufficient radial force when expanded to support the artery wall.
Data Source
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AI summary
To provide a bioabsorbable stent including: a first tubular unit containing a plurality of cells coupled to each other, each of the cells formed from substantially linear parts and a substantially circular arc part and having a substantially U shape which opens to one end in the axial direction of the stent; and a second tubular unit having the same shape as that of the first tubular unit, the second tubular unit containing a plurality of cells each of which has a substantially U shape which opens to a direction opposite to the opening direction of the opposing first cell. The first tubular unit and the second tubular unit are alternately arranged in sequence to surround a central axis of the stent. Coupling members couple substantially linear parts in some of the opposing cells in the respective neighboring tubular units. A ratio of a width (wT) of the cell line at the top of the circular arc part to a width (wS) of the cell line at the substantially linear part, a ratio of a cell height (h) to a cell width (w), and a maximum principal stress (σmax) at the time of expansion are selected appropriately.