Search Results (1,293)

Background: Conventional transdermal drug delivery systems are often limited by poor skin permeability and low drug loading efficiency, necessitating the development of advanced delivery platforms. Objectives: This study aimed to develop and optimize photopolymerizable bioinks (PBs) for liquid crystal display (LCD)-based 3D printing of crosslinked hydrogel microneedles (cHMNs) to enhance transdermal delivery of estradiol valerate (E2V). Methods: A Box–Behnken design (BBD) was used to optimize the effects of Gantrez™ S-97, Jurymer™, and polyvinyl alcohol (PVA) on viscosity, exposure time, hardness, and elasticity, with strong predictive performance (R² = 0.9702–0.9907). Results: Estradiol valerate-loaded nanoparticles (E2V-NPs) were prepared via ionotropic gelation, exhibiting a particle size of 698.33 (0.78) nm, PDI of 0.50 (0.06), zeta potential of −39.09 (7.32) mV, and high encapsulation efficiency (86.87 (0.78)%). The optimized PBs enabled fabrication of uniform cHMNs (~800 µm height) with adequate mechanical strength (hardness 20.45 (1.23) N; elasticity 2.97 (0.49) MPa) and effective insertion capability. The E2V-NPs-loaded cHMNs exhibited sustained drug release over 12 days (~56.92 (4.27)%). Skin permeation studies showed a significantly enhanced flux (10.81 (4.55) µg/cm²/h) and cumulative permeation (12.94 (2.06) µg/cm²) compared to topical E2V-NPs and suspension, along with increased skin accumulation (38.55 (0.10) µg). Cytotoxicity studies confirmed that E2V and E2V-NPs were biocompatible (>80% viability), while PBs showed concentration-dependent cytotoxicity. Conclusions: Overall, this integrated platform combining design of experiment, nanoparticles, microneedles, and LCD 3D printing offered a promising strategy for enhancing transdermal drug delivery efficiency and reproducibility. Full article

Objectives: Limited information is available on how connector size and luting protocols influence the fracture resistance of 3D-printed resin-based fixed dental prostheses (FDPs). This in vitro study evaluated the effect of connector size and luting agent type on fracture load. Methods: Eighty 3-unit posterior FDPs were 3D-printed (GC Temp PRINT, GC Corp.) and assigned to eight groups (n = 10) by connector size (GroupA 5 × 5 mm or Group B 3 × 3 mm) and luting protocol (1: no cement; 2: TempBond temporary cement; 3: Ketac Cem glass ionomer; 4: G-Cem One self-adhesive resin cement). Specimens were seated on standardized metal abutments and loaded to failure (Instron 5567, 1 mm/min). Data analyzed by Shapiro–Wilk normality test, Mann–Whitney U (connector size), ANOVA/Kruskal–Wallis (luting within size; α = 0.05). Results: Connector size significantly affected fracture resistance (Mann–Whitney U, p < 0.001): 5 × 5 mm groups showed ~3× higher loads (1468–1638 N) than 3 × 3 mm groups (266–384 N). In 5 × 5 mm groups, luting protocol had no significant effect (ANOVA, p > 0.05). In 3 × 3 mm groups, resin cement (343 N) and temporary cement (384 N) showed higher loads than no-cement controls (266 N; Kruskal–Wallis p = 0.022, exploratory U p < 0.05); glass ionomer showed no significant difference. Conclusions: Within the limitations of this in vitro study, larger connectors substantially increased 3D-printed FDP fracture resistance. Resin-based luting agents increased loads in smaller-connector FDPs. Full article

Stenting is a minimally invasive treatment used in managing peripheral artery disease (PAD). However, clinical challenges persist, including in-stent thrombosis and restenosis, primarily driven by axial foreshortening or elongation and suboptimal balance between radial stiffness and flexibility inherent to conventional stent designs. This study proposes an innovative arrow-shaped geometry exhibiting zero Poisson’s ratio (ZPR) behaviour for 3D-printed self-expanding Nitinol stents. The complete stent deployment process was modelled using finite element analysis (FEA), including radial crimping and subsequent expansion to enable systematic parametric investigation while accounting for µ-3D printing constraints. Response surface methodology (RSM) rigorously evaluated mechanical performance, defining peak stress, chronic outward force (COF), radial resistive force (RRF), and foreshortening (FS) as constraint and objective functions within the optimisation framework. The optimised ZPR stent achieved favourable performance: extremely low foreshortening (|FS| ≤ 0.12%), representing outstanding axial stability compared with previously reported self-expanding stents, and a well-balanced radial response with ~50% higher radial strength than positive Poisson’s ratio (PPR) structures, while 16.67% lower than negative Poisson’s ratio (NPR) counterparts. These results highlight the ZPR stent’s capability to minimise axial deformation while maintaining adequate radial support, highlighting substantial potential for precise, stable deployment in PAD applications. Full article

Background/Objectives: 3D printing of removable dentures and temporary crowns and bridges is currently one of the fastest-developing technologies in prosthetic dentistry. However, little is known about the effect of different beverage solutions on the strength and color of 3D-printed denture resins. The study aimed to determine the effect of coffee, red wine, 40% ethyl alcohol, and water (reference samples) on six 3D-printed denture resins (Denture 3D+ (Nexdent); Vita Vionic (Vita), Lucitone Digital Print 3D (Dentsply), DX Denture Flex (Dentex); Formlab Denture Base (Formlabs, Optiprint Dentona). Materials and Methods: Resin samples measuring 3.3 × 10 × 65 mm (144 total) and disks 1 × 20 mm (108 total) were produced using an Asiga printer. The printed materials were then stored in coffee, red wine and distilled water and vodka for 30 days. After this time, they were subjected to a flexural strength (FS) test and the measurement of color change (CC), and compared to reference samples measured before contact with the solutions. One- and two-way ANOVA were used for statistical analysis to compare samples before and after contact with the solutions. Results: The vodka solution affected the materials’ FS—the strength was reduced from 10% (Lucitone) to 88% (Detax). For the sample with the most significant FS reduction, the elastic modulus could not be determined. The largest CCs were observed for coffee (E = 22.66 ± 1.26), and red wine (E = 21.04 ± 0.70), whereas vodka had the least effect on CC (Lucitone E = 1.04 ± 0.41 and Form Labs E = 1.31 ± 0.85). Conclusions: 3D-printed resins are susceptible to the effects of commonly consumed substances, such as coffee, vodka, and red wine. When designing and manufacturing removable prosthetic restorations, it is necessary to carefully consider the dietary habits of patients and the materials from which the removable prosthetics are printed. Full article

We present a material distribution topology optimization (TO) framework that directly generates capacity-specific radial trims for severe-service control valves. The method uses an out-of-plane resistance modified two-dimensional turbulence model and objective functions that maximize directional change to create tortuous pressure-staging geometries at predefined channel depths. Four trims targeting non-dimensional capacities ($C_V$) of 0.672, 0.96 (two objectives), and 1.248 were optimized, MSLA-printed, and tested in a globe valve using IEC 60534 procedures. The measured capacities ranged from −13.7% to +4.8% of the targets for a fully 2D optimization process, dropping to a maximum of 7.8% when coupled with a hybrid 3D tuning step. Acoustic detection indicated incipient cavitation at a pressure drop ratios greater than $0.87$ for the most highly staged design and $0.73$ for the highest capacity design, which is consistent with our simulations of the flow field before fabrication. These results demonstrate that TO can deliver fit-to-service, capacity-tuned trims with excellent cavitation suppression, reducing reliance on large parametric design libraries. Full article

Color results from the interaction of objects with varying wavelengths of light and the human visual system’s perception under different illumination conditions. In this study, special emphasis was placed on examining how varying illumination conditions and measurement geometries affect the color appearance and optical properties of printed effect pigments. Two distinct groups of pigments were examined: three interference pigments (M-series) based on calcium–aluminum borosilicate substrates, and three multicolor pigments (C-series) based on silicon dioxide. To ensure comparability of the results, all pigments were printed using screen printing techniques onto black PVC film. Characterization involved using a multi-angle spectrophotometer to measure CIEL*a*b* values, chroma (C*), and hue (h*) under CIE standard illuminants D50, A2, and F2 at a fixed illumination angle of 45° and aspecular angles of −15°, 15°, 25°, 45°, 75°, and 110°. Furthermore, the research methodology included the evaluation of lightness difference (∆L*), color differences (∆E*), chroma difference (∆C*), and hue difference (∆H*), with the D50 illuminant chosen as the reference and A2 and F2 as sample illuminants. The flop index (FI), as the indicator of lightness change at different scattering angles, was calculated for all printed pigments under all three standard illuminations. This multidisciplinary approach provided a deeper understanding of the relationship between pigment structure, illumination conditions, and viewing angles in our visual perception of printed pigments, which is of great importance for the development and optimization of goniochromatic materials. The results showed that while A2 and F2 illuminants have a negligible impact on lightness differences across all pigments, they induce noticeable variations in color, chroma, and hue differences, particularly at near-specular angles (−15° and 15°). Conversely, these differences become negligible at far-aspecular angles (75° and 110°). Furthermore, flop index (FI) analysis revealed that despite the larger borosilicate flakes in the M-series, the silicon dioxide-based C-series pigments exhibited the highest overall flop effect, with pigment C1 maintaining consistently high FI values under all illuminants. Full article

Objectives: A customizable 3D-bioprinted core-in-shell platform was developed for time-dependent oral colon delivery of live microorganisms. The system conveyed Lacticaseibacillus paracasei as a model bacterial species within a monolithic core, which was surrounded by a swellable hydroxypropyl cellulose barrier, imparting a lag phase of programmable duration, and by an enteric outer layer, protecting the dosage form during unpredictable gastric residence. Methods: Pastes of different compositions were investigated to shape the core. Core and core-in-shell units were fabricated from digital models using a bioprinter equipped with a high-precision plunger dispenser and pressure-based thermoplastic printhead. The printed units were characterized in terms of mass, dimensions, mechanical properties and release performance using paracetamol as a reference tracer. Bacterial viability was evaluated during screening of the formulation components and after each processing step by manual counting of colony-forming units. Results: A mannitol-based formulation was selected for fabrication of the core, offering a favorable balance of printability, physico-technological properties, release behavior and ability to preserve bacterial viability. Two-layer core-in-shell systems were manufactured via a dual-printing operating mode. The desired in vitro performance was attained, with no release under acidic conditions, a lag phase in pH 6.8 fluid and a subsequent release profile comparable with that generated by the core as such. Viability studies demonstrated that compounding, core printing, shell deposition and drying did not adversely affect L. paracasei survival. Conclusions: 3D bioprinting was proved to be a versatile technique for the manufacturing of oral colon delivery systems containing probiotics or live biotherapeutics. Full article

Background/Objectives: Computer-aided surgical planning (CASP) technologies, including virtual surgical planning (VSP), 3D printed cutting guides, and patient-specific implants, have been increasingly applied to deep circumflex iliac artery (DCIA) free flap reconstruction of maxillofacial defects. Despite growing adoption, no systematic review has specifically evaluated their accuracy and clinical outcomes. This study aimed to comprehensively assess the impact of CASP on reconstruction accuracy, operative efficiency, flap survival, and implant rehabilitation in DCIA flap surgery. Methods: A systematic search of PubMed, Web of Science, and Google Scholar was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines. Studies reporting CASP-assisted DCIA free flap reconstruction with three or more patients were included. Methodological quality was assessed using the Methodological Index for Non-Randomized Studies (MINORS) checklist and the Cochrane Risk of Bias 2.0 tool for the randomized controlled trial (RCT). Results: Thirty studies (1 RCT, 13 comparative, and 16 non-comparative) involving 844 patients were included. VSP with 3D-printed cutting guides was the most frequently used technology (n = 22). Mean linear deviations between planned and actual outcomes ranged from 0.40 to 4.4 mm, with most studies reporting 0.7–2.7 mm. The sole RCT demonstrated significantly better accuracy (1.3 vs. 5.5 mm, p < 0.001) and shorter reconstruction time (16 vs. 39 min, p < 0.001) with CASP. Flap survival ranged from 90% to 100%. Conclusions: CASP technologies, particularly VSP with 3D-printed cutting guides, appear to improve the accuracy and predictability of DCIA flap reconstruction. However, the evidence base is predominantly retrospective and heterogeneous; prospective multicenter studies with standardized outcome measures are needed before definitive clinical guidelines can be established. Full article

This study investigates the station planning problem of a mobile manipulator for robotic 3D concrete printing. The problem is formulated as a station planning problem considering two trajectory-level performance objectives: kinematic dexterity and structural stiffness. A directional dexterity metric based on the minimum normalized velocity directional manipulability along the task path is used to evaluate the worst-case motion capability of the manipulator during trajectory execution. A stiffness-related metric based on the maximum absolute Z-axis deformation of the end-effector is used to evaluate the worst-case deformation under operational loads. These two trajectory-level criteria are normalized and integrated through a weighted scalarization strategy, and a genetic algorithm is employed to search for station configurations under reachability constraints. Case studies on representative wall geometries show that the proposed method improves motion performance and reduces deformation compared with non-optimized station placements. The results indicate that the proposed framework provides an effective station planning strategy for mobile manipulators in trajectory-following robotic tasks. Full article

The qualification of additively manufactured (AM) components produced from engineering polymers poses unique challenges, particularly when evaluating mechanical properties according to ASTM D638. The application of high-performance thermoplastics, such as ULTEM™ 9085 and ULTEM™ 1010, frequently relies on manufacturer-provided datasheets for qualification. However, existing datasheets do not provide guidance specific to articles printed in the XY plane, which can be complicated by failures that initiate at microstructural anomalies rather than being driven by intrinsic material behavior. The objective of this study was to investigate the performance and qualification of ULTEM 9085™, examined according to ASTM D638, and pursue improvements through refined print parameters. A significant improvement in strength and conforming failures was achieved with modest adjustments to the print settings. For Type 1 samples printed with ±45° infill, gage section failures improved from only 5% to 100%, while samples with 0/90° infill achieved 80%. Correspondingly, the ultimate tensile strength increased from 49 ± 2 MPa to 61 ± 2 MPa and from 53 ± 3 MPa to 63 ± 6 MPa, respectively. These results underscore the critical role of process parameters, including contour overlap, in qualifying polymer AM materials, and their contribution to the performance and reliability of printed components. Full article

Background: Twin-screw wet granulation (TSWG) is a promising continuous manufacturing technology, featuring high operational flexibility, short residence time and consistent quality. The process development of TSWG relies on the synergy of material characterization, screw configuration, and process parameter optimization. Objective: In order to fully combine various design variables, and to accelerate the process development of TSWG, a material–process–equipment integrated design (MPEID) methodology is first applied to the TSWG process of Guizhi Fuling capsule, a botanical drug product. Methods: First, an equivalent formulation was designed to save trial costs. Second, 3D printing technology was used to customize both conveying and kneading elements with the lead, with the kneading discs stagger angle (SA) and the thickness (thick) as screw element variables. The position of fabricated kneading elements was varied to generate different screw configurations. Then, the critical screw parameters (CSPs) and critical process parameters (CPPs) were identified by a two-step design of experiment (DOE) toward optimizing granule quality. Results: As a result, the SA and thick were identified as CSPs, and the liquid-to-solid ratio was the CPP. Under the optimal TSWG process conditions, the twin-screw granulator could be operated under low torque (i.e., average torque = 1.48 ± 0.06 Nm). The dried granules exhibited superior flowability, as well as highly consistent particle size distribution with industrial batches. After capsule filling, the dissolution test results showed the prepared Guizhi Fuling capsules reached 93.7% cumulative dissolution at 15 min, which approached that of commercial capsules (i.e., 93.0%). Conclusions: This study demonstrated the feasibility of proposed MPEID methodology, supporting the efficient and cost-effective process development of TSWG. Full article

Despite major advances in polymer composites for Fused Filament Fabrication (FFF), designing environmentally sustainable materials from bio-based resources remains a key research priority. The objective of this study is to check the processability and properties of sustainable PETG/cork composites processed via FFF technology. Filaments with 5 and 10% of cork were created using a twin-screw extruder. Samples from these filaments were printed by FFF technology, and subsequently subjected to morphological, thermal and mechanical testing. As a result of the study, it was proved that the 3D-printing process did not result in a tensile strength decrease with an increasing cork percentage, as observed in mechanical testing of the filament. The addition of cork significantly increased plasticity without decreasing tensile strength when introducing 10% of cork particles. The interfacial temperatures of the prepared composites did not differ much from the polymer matrix and were 79.55 °C, 77.56 °C, 76.67 °C for PET-G, PET-G + 5% cork, and PET-G + 10% cork, respectively. Thermal conductivity decreased significantly as the percentage of cork increased. This work shows that FFF technology is one of the most suitable manufacturing options for PETG + 10% cork composites to produce things with low conductivity and the same thermal and mechanical properties as pure PETG. Full article

Background/Objectives: Tooth discoloration can influence the esthetic outcome of restorative treatments. Recently, 3D-printed ceramic-filled hybrid materials have been introduced for dental restorations using digital workflows. The aim of this in vitro study was to evaluate the influence of 3D-printed ceramic-filled hybrid veneers on the final color of discolored teeth using spectrophotometric measurements. Methods: Twenty-five extracted human anterior teeth without caries or restorations were prepared for veneer restorations using standardized reduction protocols. Artificial discoloration was induced by applying light-cured color coatings to the buccal surfaces of the specimens. The prepared teeth were digitally scanned, and veneers with a thickness of 1 mm were designed and fabricated using a 3D printing system and a ceramic-filled hybrid material. Color measurements were performed with a spectrophotometer and recorded in the Commission Internationale de l’Éclairage L*a*b* (CIELAB) color system. Measurements were obtained at four stages: after creation of discoloration, after two weeks of immersion in physiological saline solution, after veneer placement using neutral try-in gel, and after two months of immersion following veneer placement. Color differences were calculated using three color difference formulas (ΔE*ab, ΔE94, and ΔE00). Results: The placement of the 3D-printed veneers produced substantial modifications in the optical characteristics of the discolored substrates, reflected by reduced chroma values and significant color differences between the baseline and veneer stages. After two months of immersion, only minor variations in color coordinates were observed. The calculated color differences between the veneer stage and the post-immersion stage remained low across all evaluated color difference formulas, indicating good short-term color stability of the veneered specimens. Conclusions: Within the limitations of this pilot in vitro study, 3D-printed ceramic-filled hybrid veneers demonstrated the ability to effectively modify the color of discolored substrates while maintaining relatively stable optical properties after two months of immersion. These restorations may represent a promising and cost-effective option for the esthetic management of discolored teeth. Full article

This paper presents a hybrid methodology for the creation of educational mobile robots, combining the efforts of developers in design, construction, and instrumentation with the use of “Vibe Coding” as an alternative programming approach. To achieve this objective, the methodology integrates electronics and algorithmic thinking to enable adaptive behavior across three operating modes for robotics competitions. The mobile robot features a compact and modular architecture (430 g, 22 cm length × 14 cm width) with support components manufactured using 3D printing. Instrumentation included an Arduino Uno^® development board, a Syb-170^® proto shield, a buzzer, an HC-SR04^® ultrasonic sensor, an SG90 RC^® servomotor, a SSD1315 display, three TCRT5000^® reflective optical sensors, two DC motors with integrated 48:1 gearboxes, an L298N motor driver, and two 18650^® rechargeable lithium-ion batteries. Programming and algorithmic implementation were carried out using Vibe Coding, leveraging its intuitive environment to accelerate the development of three independent operating modes: (1) line follower on a racetrack, (2) obstacle avoidance with various objects, and (3) Bluetooth control via the free MIT Application Inventor. The mobile robot successfully demonstrated all three tasks, validating its suitability for educational and competitive purposes. Furthermore, its architecture supports AI-assisted decision-making through Vibe Coding, enabling dynamic responses to environmental disturbances. The multimodal configuration enhances navigation by correcting trajectory deviations, thereby improving robustness, adaptability, and overall functionality. Full article

Joining dissimilar polymers such as polypropylene (PP) and high-density polyethylene (HDPE) remains a challenge in modern manufacturing due to their incompatible thermal properties and poor interfacial bonding. In this study, a novel hybrid structure was fabricated by laser welding of PP to an HDPE matrix reinforced with 3 wt% carbon nanotubes (CNTs). The CNTs were incorporated via fused filament fabrication (FFF) 3D printing to raise the melting temperature and thermal stability of HDPE, thereby minimizing the thermal mismatch with PP. A pulsed CO₂ laser was used to perform butt welding, and the influences of pulse frequency, welding speed, and laser power on the elastic modulus and tensile properties of the weld samples were thoroughly studied. A response surface design was employed to build predictive models and perform multi-objective optimization. The addition of CNTs, as evidenced by differential scanning calorimetry (DSC), elevated the crystallinity level of HDPE from 48.3% to 53.1% and the melting point from 137.8 to 140.8 °C, making its thermal properties more comparable to those of PP. Observations via scanning electron microscopy (SEM) indicated that when the optimal parameters were applied (pulse frequency: 35 Hz, welding speed: 21 mm/s, and laser power: 49 W), the joint line was defect-free, fully fused, and contained very few voids. At these settings, the model estimated an elastic modulus of 793 MPa and a tensile strength of 49.6 MPa, while confirmation experiments yielded 47.2 MPa and 764.5 MPa, respectively, with relative errors below 5%. The results demonstrate that the combination of CNT-assisted laser welding and RSM-driven optimization effectively resolves the thermal incompatibility of HDPE and PP, thereby facilitating high-quality joining of dissimilar polymers for applications in packaging and automotive fields. Full article