Erika García-López

This work presents the manufacture of thin-wall thermoplastic polyurethane (TPU) structures (200 to 400 µm thick) via microinjection molding (µIM) for heart valves. A Moldflow simulation confirmed the number of gates required for a complete filling. These predictions were used as a qualitative process window-mapping tool, translated into plunger machine setpoints, and adjusted experimentally on the Babyplast 6/12 P. The simulation predicted volumetric shrinkage of 7.3% and wall shear stress of 0.60 MPa. Tooling characterization was performed using 3D optical profilometry, which quantified surface topography and related roughness (Avg. ~2.0876) to evaluate polymer flow. Dimensional verification was performed by 3D laser scanning against the nominal CAD model. The study demonstrated that Moldflow Insight overestimates the pressure requirement by a factor of two (145.0 MPa predicted vs. 78 MPa experimental) when applied to a plunger-based microinjection unit in submillimeter parabolic cavities. A methodology for translating simulation outputs into plunger machine setpoints, including the hydraulic-to-melt pressure amplification ratio and a position-based V/P switch-over criterion, is presented.

In this article, a diode‐pumped solid‐state laser marking system (maximum average power, 25 W; wavelength, 1064 nm) is used to texture Ti6Al4V substrates. This investigation examines the effect of varying marking speed (50 and 150 mm s ⁻¹ ) and average power (21.25 and 23.75 W), corresponding to linear energy densities ranging from 0.142 to 0.475 J mm ⁻¹ . Surface characterization is performed using a 3D focus variation microscope, atomic force microscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, and contact angle measurements. Surface roughness variations from 0.71 to 1.004 μm are shown after applying linear energy densities of 0.425 and 0.475 J mm ⁻¹ , respectively. A microstructural study demonstrates a reordering of the α and β titanium phases. The applied energy significantly influences surface morphology and chemical composition, increasing the oxygen content and indicating surface oxidation. Under this study's processing and measurement conditions (sessile drop with artificial saliva), all textured samples exhibit increased contact angles (from 95 ± 5° for the substrate to 116.03 ± 6.32° and 118.9 ± 6.8° for the textured samples), indicating a shift toward more hydrophobic behavior. The combined effects of increased micro‐roughness and oxide formation explain this trend.

Magnesium-based coronary stents have gained significant interest due to their excellent biocompatibility, biodegradability, and mechanical properties. However, a key limitation of magnesium in biomedical applications is its low corrosion resistance, which compromises its structural integrity and mechanical strength over time. Polymeric coatings can overcome this challenge, enhancing magnesium-based implants’ corrosion resistance and overall performance. This study applied a polylactic acid (PLA) nanofiber coating to WE43 magnesium (Mg) stents via electrospinning to reduce their corrosion rate. Both uncoated and coated stents underwent in vitro immersion tests in Hank’s solution for 1, 3, 7, and 14 days. The effectiveness of the PLA coating was evaluated through morphological analysis, chemical composition assessment, corrosion behavior (weight change), magnesium ion release, and in vitro biocompatibility. The corrosion observed in the uncoated WE43 stents indicates that protective coatings are necessary to regulate degradation rates over extended implantation periods. The results demonstrated that coated stents exhibited improved performance, maintaining the integrity of the PLA coating for up to 14 days. The coated stents demonstrated reduced surface damage and lower weight loss resulting from lower magnesium release. In our study, the coated stents demonstrated a reduced corrosion rate (0.216 ± 0.013 mm/year) compared with the uncoated stents (0.312 ± 0.010 mm/year), both after 14 days. Additionally, in vitro biocompatibility results confirmed the non-toxic nature of PLA-coated stents, which enhances cellular proliferation and contributes to a more favorable environment for vascular healing. These findings suggest that PLA coatings can effectively prolong the functional durability of WE43 Mg stents, offering a promising solution for enhancing the performance of biodegradable stents in cardiovascular applications.

Electrospinning has been studied to deposit polylactic acid (PLA) nanofibers on complex coronary stent geometries. The rheological properties of PLA with two molecular weights were analyzed in various solvents, including chloroform, acetone, dichloromethane, and dimethylformamide, to determine the entanglement concentration. High molecular weight PLA dissolved in a 2:1 v/v chloroform: acetone was suitable to form bead‐free nanofibers with uniform morphology. A response surface methodology was implemented to evaluate electrospinning parameters (concentration, flow rate, and voltage). The thin film mat was examined by scanning electron microscopy (SEM) to determine the size of the fibers and the fiber diameter distribution. A concentration of 8% w/v, a voltage of 15 kV, and a flow rate of 0.02 mL/min produced bead‐free nanofibers with an average diameter of around 491 ± 150 nm on a flat surface. Additionally, a PLA thin film of nanofibers was deposited on a coronary stent geometry using a rotary motor, resulting in a bead‐free uniform film with fibers measuring approximately 817 ± 388 nm.