Designing Biodegradable Stents Through Experiment and Simulation

Biodegradable stents optimisation using experiment and simulation

Biodegradable stents are an important direction in cardiovascular device development. Unlike conventional metallic stents, which remain permanently inside the body, biodegradable stents are designed to provide temporary mechanical support and then gradually degrade as the vessel recovers.

The concept is promising, but the engineering challenge is significant. A biodegradable stent must not only be biocompatible and structurally reliable; it must also maintain favourable blood-flow conditions as its material and geometry change over time.

A recent Mansim R&D contribution, published in Materials & Design, investigates this challenge by combining experimental corrosion testing with computational haemodynamic assessment of a 3D-printed biodegradable stent and insert design.

The study focused on a novel stent placed within a bypass vessel configuration. The design includes an internal spiral-like insert intended to generate swirling flow, improve wall shear stress distribution and reduce low-flow regions near the vascular junction. These haemodynamic effects are important because disturbed flow, low wall shear stress and stagnant regions are associated with restenosis and thrombus formation.

From 3D printing to corrosion testing

The stent and insert were manufactured using two 3D-printing methods: Fused Deposition Modelling with PLA filament and Stereolithography with PLA resin. The printed samples were then immersed in simulated body fluid to assess corrosion-related behaviour.

In this work, corrosion refers to the combined physical and chemical changes observed in the PLA samples, including water absorption, surface deposition and dimensional change.

A key finding was that the samples gained weight rather than losing weight. This was attributed to fluid absorption and sediment deposition. The results also showed that the manufacturing route matters: FDM samples developed more surface sediment than SLA samples, mainly due to their higher roughness, porosity and bead-and-void microstructure. SLA samples showed better geometric fidelity and a slower, steadier change over time.

The SLA specimen was selected for the haemodynamic simulations because it most closely matched the intended geometry. FESEM imaging and 3D scanning showed local thickness increases of up to 0.1 mm after exposure to simulated body fluid.

To understand the flow impact of this change, the researchers created CFD models with thickness increases of 50%, 100% and 150% relative to the initial geometry.

The simulations were carried out in Ansys Fluent using pulsatile inlet flow and a non-Newtonian Carreau model for blood. The results showed that increasing stent and insert thickness reduced the beneficial effect of the insert.

Secondary flow shifted away from the vessel wall towards the centre, low-velocity regions increased, and the insert became less effective at maintaining favourable wall shear stress.

Why this matters for biodegradable implants

The central engineering insight is clear: biodegradable stents cannot be assessed only in their initial manufactured state. As degradation, deposition or absorption alters the geometry, haemodynamic performance can also change.

For Mansim, this work reflects a core R&D approach: connecting experimental evidence, geometry reconstruction and CFD simulations to understand complex biomedical flow problems. By linking material behaviour with haemodynamic performance, simulation becomes a practical tool for evaluating device safety, design robustness and restenosis-related risk.

As biodegradable vascular implants continue to develop, this kind of integrated workflow will be essential for designing devices that remain effective not only at implantation, but throughout their functional lifetime.