Optimising a polycaprolactone coating on a magnesium-based alloy for biomedical applications using ultrasonic atomisation and femtosecond pulsed laser ablation

Magnesium alloys have gained attention in the biomedical field for their promising potential as bioresorbable stents due to their favourable mechanical properties and biocompatibility. However, their high susceptibility to rapid degradation in physiological environments has remained a challenge. In this study, we explore the use of a polycaprolactone (PCL) coating applied via ultrasonic atomisation spray to improve the corrosion resistance of WE43 alloy. The surface of WE43 was pre-treated using femtosecond pulsed laser ablation to enhance the adhesion of the PCL coating. Laser ablation was carried out using a femtosecond laser with varying parameters to generate surface features promoting coating adhesion. Next, samples were coated with PCL in varying cycles, followed by in vitro corrosion tests and characterisation. Electrochemical impedance spectroscopy and potentiodynamic polarisation tests were performed to assess corrosion behaviour. The results indicate that laser-ablated WE43 exhibits a corrosion rate up to 5 times lower than untreated WE43. Furthermore, laser-ablated PCL-coated samples exhibited an improved corrosion resistance with the 60-cycle PCL showing optimal performance. Surface analysis using SEM, XPS, and EDS confirmed the homogeneity and chemical stability of the PCL coatings. The scratch tests show an increased adhesion of PCL to magnesium more than ten times, highlighting the effectiveness of laser-assisted PCL coatings in bioresorbable stent applications. Compared to prior literature, this dual-step laser-assisted coating method represents a significant advancement by achieving simultaneous improvements in corrosion resistance, coating adhesion, and biocompatibility—key barriers in the clinical translation of magnesium-based implants.