Polymeric Stent Laser Pattern Formation
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Solution Overview
Problem
Existing methods for manufacturing polymeric stents using lasers often result in overheating and degradation of biodegradable polymers, leading to reduced mechanical strength and performance due to heat-affected zones, and there is a need for improved mechanical strength and biodegradability while maintaining molecular weight and polydispersity index.
Innovation Solution
The use of a second harmonic generator laser with a wavelength ranging from 940 nm to 1552 nm, converted to 470 nm to 776 nm, to form patterns on polylactic acid tubes with ultra-short pulse widths, reducing thermal injury and maintaining molecular weight and polydispersity index, resulting in stents with enhanced mechanical strength and biodegradability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional laser methods are used to manufacture polymeric stents, then manufacturing efficiency is improved, but thermal damage occurs leading to reduced mechanical strength
Solution Approach 1:
The patent applies parameter changes by switching from conventional continuous-wave or long-pulse lasers to ultra-short pulse lasers with pulse widths of 10 ps or less. This fundamental parameter change in laser pulse duration eliminates thermal accumulation and heat-affected zones, allowing high-speed manufacturing while preserving the mechanical strength of biodegradable polymers by preventing thermal degradation.
Solution Approach 2:
The patent employs periodic action through ultra-short pulse laser irradiation, where the laser delivers energy in extremely brief pulses rather than continuous exposure. This periodic delivery method allows the polymer material to cool between pulses, preventing heat buildup and thermal damage while maintaining high manufacturing efficiency through rapid pulse repetition.
2Speed
If conventional laser methods are used, then manufacturing speed is improved, but molecular weight degradation occurs reducing biodegradability
Solution Approach 1:
The patent changes the laser pulse duration parameter to ultra-short pulses (10 ps or less), which delivers energy so rapidly that it ablates or modifies the polymer surface without causing thermal degradation of the molecular chains. This parameter change enables high-speed manufacturing while preserving the molecular weight and polydispersity index, thereby maintaining the biodegradability characteristics of the polymer.
Solution Approach 2:
The patent replaces the thermal-mechanical laser processing mechanism with a photo-ablation mechanism using ultra-short pulse lasers. This substitution eliminates the thermal field that causes molecular weight degradation, allowing high-speed processing through purely optical interaction with the polymer material without compromising compositional stability.
3Productivity
If conventional laser methods are used, then processing efficiency is improved, but heat-affected zones are created reducing stent performance
Solution Approach 1:
The patent uses periodic ultra-short pulse laser irradiation where each pulse is so brief (10 ps or less) that thermal diffusion is minimized. The periodic nature of the pulses allows heat to dissipate between pulses, preventing the formation of heat-affected zones while maintaining high processing efficiency through rapid sequential pulsing.
Solution Approach 2:
The patent fundamentally changes the laser pulse width parameter to ultra-short durations, which transforms the heating mechanism from conductive thermal diffusion to direct photo-ablation. This parameter change eliminates heat-affected zones by confining energy deposition to the immediate focal point without thermal spread, enabling efficient processing without thermal damage.
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 method achieves polymeric stents with superior mechanical strength, capable of withstanding expansion beyond the target diameter without fractures, and optimal biodegradation, while minimizing thermal damage and maintaining molecular weight and polydispersity index, thus addressing the limitations of prior art.
Implementation Method 1
forming a pattern on a polymer tube with a laser; wherein the pattern formed on the polymer tube comprises a plurality of repeating units... In some embodiments, the pattern is formed on the polymer tube using a second harmonic generator laser in which a wavelength ranging from about 940 nm to 1552 nm or less is converted.
Implementation Method 2
The use of a second harmonic generator laser with a wavelength ranging from 940 nm to 1552 nm, converted to 470 nm to 776 nm, to form patterns on polylactic acid tubes with ultra-short pulse widths, reducing thermal injury and maintaining molecular weight and polydispersity index
Data Source
AI summary
A method of manufacturing a polymeric stent by forming a pattern on a polymer tube with a laser, where the pattern formed on the polymer tube comprises a plurality of repeating units comprising a plurality of unit cells, each having a V-shaped configuration and polymeric stents formed by the methods. The pattern may be formed on the polymer tube (e.g., polylactic acid tube) using a second harmonic generator laser in which a wavelength ranging from 940 nm to 1552 nm is converted.