Job offer

Organisation/Company Université de Bretagne Occidentale Department Faculty of Sciences Research Field Engineering » Materials engineering Researcher Profile First Stage Researcher (R1) Positions Master Positions Application Deadline 30 Mar 2026 - 23:59 (Europe/Paris) Country France Type of Contract Temporary Job Status Full-time Hours Per Week 35 Is the job funded through the EU Research Framework Programme? Other EU programme Is the Job related to staff position within a Research Infrastructure? No

Offer Description

Atherosclerosis is a disease characterized by the progressive accumulation of a lipid core and cellular debris within the arterial wall, resulting in the formation of an atheromatous plaque. This inflammatory process leads to stenosis, limiting oxygen supply to tissues, or to plaque rupture, triggering an acute thrombotic event. To restore normal hemodynamics, blood flow has historically relied on angioplasty. This procedure involves introducing a balloon catheter that inflates to crush the plaque and widen the artery. However, angioplasty alone has limitations: the artery often undergoes immediate elastic recoil or medium‑term cicatricial restenosis. To overcome these mechanical failures, stent implantation has become the standard of care.

A stent is a mesh tubular prosthesis, generally made of metal or biodegradable polymer. Its thickness varies from 60 to 80 μm for metal, compared to 120 to 170 μm for biodegradable polymers. Its length ranges from 10 to 30 mm for coronary arteries and can reach 80 mm for peripheral arteries. Its diameter ranges from 1 to 5 mm for the coronary network and up to 12 mm in the periphery. Crimped onto the catheter balloon, the prosthesis is deployed against the arterial wall during balloon inflation and remains fixed there. Its role is to maintain the diameter of the arterial lumen and stabilize the atheromatous plaque. To limit the cellular proliferation responsible for restenosis, stents are often equipped with an active polymer coating that releases a drug in a controlled manner. Despite these advances, current geometries require a complex compromise between mechanical properties (flexibility, radial strength, durability), conformability, and biocompatibility. The transition to biocompatible polymer materials accentuates these structural challenges. Based on these facts, this thesis aims to explore new architectures based on polymer meta‑structures to optimize the vascular behaviour of coronary arteries.

In this study, stents will be produced by additive manufacturing (stereolithography). In the first phase, the polymer resin will be selected, followed by the validation of printing and manufacturing protocols. To this end, several types of resins will be tested using dogbone‑type specimens. These will be manufactured at different printing angles (from 0° to 90°) (1) by varying process parameters (resin temperature, layer thickness), as well as cleaning and post‑treatment steps (UV exposure duration and temperature). The objective is to perform quasi‑static tensile tests (monotonic and loading‑unloading cycles) on these specimens and examine their time‑dependent response (relaxation, creep, and/or fatigue tests). The results will allow for the identification of elastic parameters (Young’s modulus and Poisson’s ratio) and the estimation of the anisotropy induced by the printing orientation. A constitutive model capable of describing the material response under a wide range of loads will be proposed. The choice of the final protocol and material will be based on measurement repeatability and optimization of mechanical performance. In a second step, the study will focus on the characterization of thin tubular structures, which represent a crucial step regarding the intended application. Thus, several specimens with different thicknesses, lengths, and diameters will be tested in compression (radial and longitudinal), as well as in torsion. These tests will be carried out under quasi‑static and high‑cycle fatigue conditions. The results will enrich the constitutive model established in the first phase and measure additional mechanical quantities such as compressive stiffness, buckling, and torsional strength. Finally, fatigue tests will be used to plot Wöhler curves to define a failure criterion. This characterization is imperative to predict the stent’s lifespan, as it is subjected to millions of cycles due to heartbeats.

The results of the characterization campaign of the first phase will form the foundation for optimizing the stent geometry, which will be realized during the second phase of the project. This second phase will revolve around a finite element numerical study and its validation through mechanical testing. The objective will be to evaluate the impact of the unit cells’ geometric parameters (size, length, thickness), their density (longitudinal and circumferential), and their arrangement within the final structure. This approach is crucial because the significant thickness of current polymer stents disrupts blood flow, thereby increasing the risk of thrombosis. The meta‑structure concept aims to meet this challenge through topological mesh optimization. This design must reconcile several mechanical imperatives: i) maintaining sufficient radial force to ensure blood canal patency, ii) resistance to torsion, and iii) fatigue strength. Furthermore, the predictability of the meta‑structure’s expansion during deployment will be studied, along with radial and longitudinal elastic recoil, to prevent any local arterial injury. A fundamental aspect of the study will also address the device’s flexibility: the stent must be able to navigate coronary arteries that often have complex geometries without causing vascular trauma. In this regard, the choice of polymer resin and mesh geometry will be decisive and optimized through numerical simulation. These will be validated by mechanical tests (compression, fatigue, torsion) on optimized prototypes produced by 3D printing. A collaboration with cardiologists from the Brest University Hospital (CHU de Brest) will ensure a realistic approach for clinical applications. In parallel, the study integrates a multiphysics dimension dedicated to the simulation of the stent‑internal endothelial wall assembly. This approach requires expertise in fluidics and continuum mechanics.

In the third phase, the integration of an antenna and MEMS sensors will allow for the documentation of mechanical anomalies and the transmission of this data in real‑time. The challenge is threefold: to guarantee an optimal compromise between biocompatibility, conformability, and mechanical strength, while offering, through connectivity, personalized medicine that enhances patient autonomy.

Research facilities and resources

The various experimental and modelling equipment are available within the two units hosting the work, IRDL UMR CNRS 6027 and Lab‑STICC UMR CNRS 6285. The thesis is supervised by an Associate Professor (HDR) and a University Professor (each associated with one of the two UMRs). The supervision team also includes a recently recruited Associate Professor, a research engineer, and a technician.

Where to apply

E‑mail

Requirements

Research Field Engineering » Materials engineering Education Level Master Degree or equivalent

Skills/Qualifications

The candidate must hold an engineering degree or a Master of Research, or an equivalent degree in Mechanics. They should have strong skills in experimental material characterization (mechanical testing, image correlation, SEM). Skills in additive manufacturing, finite element numerical simulation, and biomechanics will be highly appreciated.