SEM Analysis of Medical Stents
Introduction
Medical stents are small, mesh-like tubes inserted into narrowed or blocked passageways in the body to keep them open. Most commonly used in blood vessels, they are also employed in the esophagus, bile ducts, or ureters. Their performance depends on material properties, manufacturing precision, and surface condition.
Scanning Electron Microscopy (SEM) provides high-resolution imaging and surface analysis, making it indispensable in the development, quality control, and failure analysis of medical stents. This application note outlines how SEM is used in stent evaluation, with examples based on secondary electron detection (SED), backscattered electron detection (BSD), and integrated energy-dispersive X-ray spectroscopy (EDS). These capabilities—combined in systems like the Semplor NANOS tabletop SEM—support a comprehensive investigation of surface morphology, material composition, and structural integrity.
What Are Stents Used For?
Medical stents are used to support narrowed or weakened passageways in the body. Their most common applications include restoring blood flow in coronary arteries and improving circulation in peripheral vessels.
Coronary Artery Disease (Heart Stents)
Stents are often placed in the coronary arteries to reopen narrowed vessels caused by atherosclerosis. These procedures restore blood flow to the heart and help prevent heart attacks. Stents can also be drug-eluting, releasing medication that reduces the risk of re-narrowing.
Peripheral Artery Disease
In cases where peripheral arteries—such as those in the legs or arms—are narrowed, stents are used to maintain vessel patency and improve blood circulation.
Stents are constructed from materials chosen for their biocompatibility, flexibility, durability, and corrosion resistance. The following sections explore how SEM is used to evaluate different stent materials and their structural features.
SEM Applications for Common Stent Types
Metal Stents (Bare-Metal and Alloys)
Metal stents, including those made from stainless steel, cobalt-chromium (Co-Cr), or nitinol (NiTi), require detailed analysis of microstructure and surface integrity. These are the foundational type of stents and remain widely used in clinical practice.
Purpose:
To investigate microstructure, surface quality, and alloy composition in stents made from stainless steel, cobalt-chromium (Co-Cr), and nitinol (NiTi).
SEM Use:
High-resolution imaging of surface features using SED.
BSD imaging for material contrast and structural uniformity.
EDS mapping for full elemental composition analysis.
Tilted views and higher magnification to assess fine structural detail, such as sidewalls and joints.
The images above show a section of the stainless-steel heart stent in BSD mode (left) and an EDS map (right) which shows the full composition of the heart stent.
Bioresorbable Polymer Stents
Polymer-based stents degrade over time and often incorporate drug coatings. SEM is key to studying their surface condition and structural integrity.
Purpose:
To assess surface porosity, wall thickness, and drug integration in polymer stents.
SEM Use:
Topographic imaging (TOPO mode) to visualize surface texture and micro-porosity.
Tilted imaging reveals sidewall structure and internal porosity.
High-resolution imaging tracks degradation behavior over time.
Quantify features critical to drug delivery and mechanical performance.
The images above show the polymer stent using the NANOS’ TOPO mode. With this viewing option one can clearly resolve the topography of the sample surface. The second image from the left shows the stent tilted to 41.5 degrees and shows the porous edge of the stent. The two images on the right are higher resolution image showing this porosity is more detail.
Key SEM Applications in Stent Evaluation
Surface Morphology and Quality Control in SEM Analysis of Stents
A smooth, defect-free surface is crucial for device performance and biocompatibility. SEM helps verify manufacturing precision and surface treatments.
SEM enables:
Detection of micro-cracks, burrs, or laser-induced artifacts.
Evaluation of surface roughness and uniformity.
Mechanical Damage and Deployment Effects in SEM Stent Testing
Understanding how stents behave under mechanical stress is essential for ensuring durability and safety.
SEM enables:
Imaging of strain marks and post-expansion distortions.
Evaluation of junction strength and weld stability.
SEM Evaluation of Drug Coatings in Drug-Eluting Stents
Drug-eluting stents must maintain consistent coating thickness and adhesion to deliver therapeutic agents effectively.
SEM enables:
Nanoscale imaging of drug-polymer layers.
Detection of coating flaking, cracking, or peeling.
Material Composition and Corrosion Analysis of Stents with SEM & EDS
SEM plays a vital role in studying how materials perform in the body over time, particularly under corrosive conditions.
SEM enables:
Visualization of corrosion pits and oxidation effects.
EDS analysis of surface residues and degradation byproducts.
Failure and Retrieval Analysis Using SEM for Stent Devices
In post-use or failure scenarios, SEM helps pinpoint the origin and mechanism of stent malfunction.
SEM enables:
Fractography to identify failure initiation points.
Assessment of biological fouling, calcification, or mechanical fatigue.
Shown above an SED image of a section of the NiTi heart stent (left), and a region of the stent in BSD mode but now looking at the side of the heart stent strut (right).
Clean Imaging and Contamination Control in SEM-Based Biomedical Research
Maintaining sample cleanliness during SEM analysis is critical—especially for medical applications where even trace contaminants can compromise results or downstream biocompatibility.
To address this, the Semplor NANOS dekstop scanning electron microscope (SEM) is uniquely engineered with all sample stage motors located outside the vacuum chamber. By isolating mechanical movement from the sample environment, this design minimizes the generation of particulates that could otherwise settle on sensitive surfaces during imaging.
As a result, the Semplor NANOS tabletop SEM offers an exceptionally clean imaging environment, making it especially well-suited for high-integrity applications such as stent evaluation and other medical device investigations.
Additionally, the system’s integrated detectors—SED, BSD, and EDS—are seamlessly configured to enable simultaneous imaging and compositional analysis, further streamlining workflows for biomedical R&D and production QA environments.
Conclusion
SEM provides powerful insight into the design, manufacturing quality, and real-world performance of medical stents. Across metal alloys and bioresorbable polymers, it enables high-resolution visualization of microstructures, material defects, and drug coatings. SEM also plays a central role in failure analysis and biocompatibility assessments.
The Semplor NANOS tabletop SEM enhances this process by combining clean chamber design with fully integrated SED, BSD, and EDS capabilities—offering a robust platform for medical device development, quality assurance, and innovation.
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