TWI worked with medical devices specialist Arterius and NAMTEC to investigate the feasibility of micro-machining stent designs created by Arterius on biodegradable polymer tubes, with the use of latest technology ultra-short pulse laser systems.
Arterius is a company with a strong background in medical grade polymer manufacturing. Polymer stents are advantageous for the application of cardiovascular surgery and other venal restructuring operations.
An assessment of existing technologies for suitability of processing the highly sensitive material with great precision was undertaken at TWI by experts in laser micro-processing. Ultra short pulse laser systems were identified as the most suitable choice for this application before proceeding in the best approach of laser system useage. Such a system would be used to micro-cut, on biodegradable polymer tubes, a variety of stent designs created by Arterius. If successful it was to generate a number of preproduction qualification samples using the newly established technique and to assess the quality of the produced stents and finally investigate the broader effects of short and ultra-short laser pulses on the biodegradable polymer materials.
Process parameters were determined to suit the available system and polymer tubes, using an 800fs laser source emitting at 1552nm. A predefined number of stents were created with the identified optimum process parameters. Microscopy images and surface profiling was used to investigate the quality of the produced cuts and the results of the process. Suggestions for further improvements in the process and the manufacturing specifications of the polymer tubes were laid out based on the analysis of results. The effects of short laser pulses were further investigated for cleaning debris from the tubes.
It was concluded that:
- The process of cutting the polymer tube material in question by ultra-short pulse laser systems is feasible.
- Improvements to the process were identified and modifications applied to the cutting system in order to accommodate the transition from metal to polymer tubing.
- Exact reproduction of the design and tightening of the primary material specifications were identified as the most important issues to address in future work.
- Debris clearance, another important aspect of the manufacturing process can be addressed by a laser based approach as well as other established methods.
- Modifications to the beam profile of current commercial systems that can be used for the cleaning process would be necessary for better results using this approach.
- The combined investigation of cutting and cleaning of biodegradable polymers can lead to effective processing of these materials for the medical industry.
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