Luigi Ambrosone

The mechanical response of foldable intraocular lenses during injector-based delivery is governed by the relaxation dynamics of their polymer networks. To quantify this behavior, we performed a comprehensive mechanical characterization over the physiological temperature range and used the resulting relaxation parameters to construct a time–temperature equivalence model. By transforming the Williams–Landel–Ferry relation to use the viscoelastic transition temperature as reference and inverting it to match the strain rate imposed by the injector, we defined an equivalent temperature that represents the thermomechanical state experienced by the material during rapid folding. This parameter converts the deformation rate into an intuitive thermal quantity, revealing whether the polymer behaves in a rubbery, viscoelastic, or frozen regime. The equivalent temperature was evaluated across a wide range of optical powers and compared with the viscoelastic transition temperature to determine the thermomechanical safety margin of each material. The distance between these two temperatures identifies whether the polymer operates in a dissipative regime, where relaxation processes are fast enough to accommodate deformation, or in a transition-limited regime, where elastic energy accumulation and microfracture become more likely. The three investigated lens families exhibit distinct thermomechanical stratification: one group consistently remains well below its transition temperature, another shows a narrow but stable margin, and the third approaches its transition temperature during folding, indicating reduced relaxation capability and increased susceptibility to edge damage. Overall, the equivalent temperature framework provides a physically grounded and clinically useful tool for modeling the prediction of risk probability linked to mechanical damage during lens implantation. It also offers a practical guideline: pre-warming the lens to its equivalent temperature places the material in the same rheological condition that it would have under slow deformation, thereby reducing the likelihood of chipping before insertion.

The release of molecular probes from soft hydrogel matrices involves coupled transport and structural relaxation processes that are difficult to capture using predefined kinetic models. Here we investigate the release dynamics of indocyanine green from bioprinted alginate-based hydrogels, including alginate-gelatin and calcium-cross-linked alginate-poly(vinyl alcohol) matrices, using a data-driven spectroscopic approach. Time-resolved UV–vis absorption spectra collected in the surrounding aqueous phase are analyzed by singular value decomposition to construct reduced-dimensional trajectories in spectral space. The spectral evolution exhibits a rapid initial increase followed by progressive saturation, indicating a transition from transient release to a quasi-stationary regime. Singular value analysis reveals an effectively low-dimensional dynamics, with two dominant modes capturing the essential temporal behavior across both systems. The resulting trajectories provide characteristic time scales and a compact, model-independent representation of release pathways directly from spectroscopic observables.

Rare-earth hydroxycarbonates and oxycarbonates are attractive functional materials because their crystal chemistry and optical response can be tailored through controlled cation substitution. In this work, Eu-doped lanthanum hydroxycarbonates with nominal europium contents of 1, 3, and 5 mol% were synthesized by combining co-precipitation and hydrothermal treatment at 140 °C for 24 h and subsequently calcined at 500 °C for 0.5 h to obtain the corresponding oxycarbonates. X-ray diffraction showed that the as-synthesized powders consist of single-phase hexagonal LaCO₃OH, while the calcined products are single-phase La₂O₂CO₃. In both structural families, systematic peak shifts with increasing Eu content indicated the formation of homogeneous substitutional solid solutions. Thermal analysis revealed a clear two-step decomposition pathway for the hydroxycarbonate precursors, with endothermic events at about 530 and 850 °C, consistent with the sequential transformation from hydroxycarbonate to oxycarbonate and, finally, to oxide. UV-Vis absorption measurements highlighted a dopant-dependent shift in the absorption edge in both hydroxycarbonate and oxycarbonate systems. Kubelka–Munk analysis showed that the estimated band-gap energy increases with Eu content, from 4.9 to 5.4 eV for LaCO₃OH-based samples and from 4.7 to 5.1 eV for La₂O₂CO₃-based samples. These results demonstrate that europium incorporation is an effective strategy for tuning the structural evolution and optical properties of lanthanum carbonate-derived materials, thus supporting their potential use in UV-responsive rare-earth-based functional systems.