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The main aim of this study was to assess the effect of ns-Nd:YAG laser structuring over zirconia green compacts on the adhesion of sintered zirconia to resin-matrix cements. Zirconia (3Y-TZP) compacts were divided according to the type of surface modification: GB -alumina grit-blasted sintered specimens; G8L -laser structured zirconia green compacts (square pattern 8 lines); G16L -laser structured zirconia green compacts (square pattern 16 lines); G8L/GB -alumina grit-blasted G8L specimens after sintering. Specimens of same group were cleaned, cemented using a dual cure resin-matrix cement and aged in distilled water for 24 h (37°C). Afterwards, the tensile bond strength was measured using a universal test machine. Specimens were analyzed by field emission guns scanning electron microscopy (FEGSEM) and white light interferometry (WLI). Laser-structured surfaces showed higher roughness values and improved morphological aspects for adhesion to resin-matrix cements. Higher tensile bond strength mean values of zirconia to resin-matrix cements were recorded for G8L (16.7 ± 3.8 MPa) and G16L (13.6 ± 3.0 MPa) groups when compared to those recorded for ordinary grit-blasted zirconia surfaces to resin-matrix cements (10 ± 3.1 MPa). The highest tensile bond strength results were recorded for the G8L/GB group (24.2 ± 7.6 MPa). The laser texturing of green zirconia surfaces promoted an increase in roughness and changes in morphological aspects of sintered zirconia for improved adhesion to resin-matrix cements.

Flexible printed electronics has attracted strong interest during the last two decades and is one of the successful trends in material science, representing the future of printed electronics (PE). This research work evaluates the use of screen-printing technology and materials for producing functional circuits for automotive interior parts, which can be subsequently processed through In-Mould Electronics (IME). Since the selection of the materials to build the printed system is of utmost importance, this study evaluates combinations of commercial polycarbonate substrates (LEXAN 8A13E, DE 1-4 060007 and LM 905 2-4 160009) and silver-based inks (ME603, ME604 and CP 6680), all suitable for IME. Different electrically conductive tracks varying in width and spacing (0.5, 0.3 and 0.2 mm) and two capacitive sensors were printed. Tensile tests and surface energy characterizations of the different polycarbonate substrates were carried out, then morphological, electrical, and thermoforming studies were performed on the printed substrates. Morphological characterization showed successful printing for wider lines (0.5 and 0.3 mm), but problems with screen clogging occurred for smaller line widths (0.2 mm). The electrical conductivity of printed tracks was in accordance to the printed layer thickness and ink solids percentage. The proof-of-concept of the electrical functionality was successful, when integrating the sensors into the PCB with SMD LEDs. Thermoforming showed limited functionality, with the best overall performance observed for specific combinations of substrate and ink. In essence, the results indicate that although all the selected substrates and silver-based inks have great compatibility among themselves and can be considered as materials for the production of functional automotive interior parts, there is no ideal pairing of inks and substrates. Therefore, this study empathizes the importance of defining product specifications for a more suitable material selection.