Search Results (877)

Microneedles (MNs) offer a transformative platform for transdermal drug delivery, though balancing structural precision with mechanical robustness remains challenging. This study utilized SLA 3D printing to fabricate high-resolution MN masters, systematically evaluating printing angles (0° to 60°) and aspect ratios to optimize fidelity. A 45° printing angle was found to significantly enhance tip sharpness and insertion efficiency. These optimized structures served as templates for flurbiprofen (FLU)-loaded dissolving MNs (DMNs) fabricated via a bilayered casting method. We investigated the impact of geometric architectures—conical, pyramidal, and star-type—on functional performance. Mechanical testing using Parafilm^® M and ex vivo rat skin revealed that the star-type design, possessing the highest vertex count, exhibited superior strength and a 100% penetration rate by effectively concentrating stress at tip edges. Consequently, star-type DMNs achieved the highest cumulative drug permeation (86.9 ± 9.9% in 12 h), outperforming pyramidal (77.8 ± 9.0%) and conical (64.4 ± 10.2%) designs. These findings underscore geometric design as a critical determinant of clinical efficacy, providing a robust framework for precision manufacturing of task-specific MNs for poorly soluble drugs. Full article

Fused Deposition Modeling (FDM) enables rapid, flexible production of polymer-based parts; however, because of additive manufacturing’s nature, it creates distinct microscale surface structures. These micro-scale surface morphologies directly affect the functional properties of the parts, such as surface roughness and wettability. In this study, the surface roughness and contact angle behavior of PLA, PETG, and ABS samples printed via FDM were investigated by varying layer thickness, print orientation, and infill density. The experimental design was created using a Taguchi L16 orthogonal array. Surface roughness was determined by optical profilometry, and wettability was measured by static contact angle tests. Surface topography was supported by scanning electron microscopy (SEM) and three-dimensional surface analyses. The findings revealed that surface roughness is predominantly dependent on layer thickness, whereas wettability is more strongly influenced by printing orientation, which determines the surface’s anisotropy. The developed artificial neural network (ANN) models successfully predicted the trends in surface roughness and contact angle outputs. This study reveals the effect of micro-scale surface structures formed in the FDM process on functional surface behavior, offering a fundamental framework for developing designable surfaces for micromechanical, microfluidic, and biomedical applications. Full article

This paper presents a high-sensitivity two-dimensional fiber-optic hydrophone designed for the detection and localization of underwater acoustic sources. The device comprises two sensing heads, each incorporating a fiber Bragg grating (FBG) embedded within a customized 3D-printed encapsulation. To enhance acoustic sensitivity, the design utilizes a silicone thin-film coupled with a pyramidal channel that spatially concentrates acoustic energy from the base to the apex, where the FBG is positioned. Incident acoustic pressure induces vibrations in the film, which are amplified by the channel structure, imparting strain on the FBG and resulting in a shift in the Bragg wavelength. The acoustic frequency response is demodulated by converting the overlapping optical power between the sensing and reference gratings into an electrical signal via a photodetector. By arranging the two sensing heads orthogonally, the system effectively determines the direction and angle of the acoustic source. Experimental results show a peak sensitivity of −210.59 dB re 1 V/μPa, with a FWHM of 57.92–66.27 Hz and a figure of merit (FOM) up to 3.64 dB/Hz. In addition, the acoustic-field SNR is approximately 26 dB in the dominant band, and the LOD is 64.19 dB re 1 μPa (10–400 Hz). Experimental validation confirms the hydrophone’s high sensitivity and localization accuracy, demonstrating its significant potential for underwater acoustic sensing applications. Full article

This study presents a straightforward process for producing a hybrid ternary composite of silver nanoparticles (Ag NPs), small graphene oxide (s-GO), and zirconia (ZrO₂) and its use as an electrode material for electrochemical sensing. The physico-chemical properties of the ternary composite were analyzed by means of field emission scanning electron microscopy (FE-SEM), ultraviolet-visible (UV-vis) and FTIR spectroscopy, X-ray Photoelectron Spectrometry (XPS) and contact angle (CA) measurements. The synthesized hybrid nanomaterial was employed as an electrode modifier in the fabrication of a modified screen-printed carbon electrode (SPCE) and used for the simultaneous electrochemical sensing of key environmental pollutants such as hydroquinone (HQ) and catechol (CAT). The developed sensor exhibited linearity in the range of 0–100 µM for both HQ and CAT, with sensitivity values of 2640 µA·mM⁻¹·cm⁻² for HQ and 5120 µA·mM⁻¹·cm⁻² for CAT. The limits of detection (LOD) were 1.5 µM for HQ and 0.72 µM for CAT, respectively. The synergistic enhancement of electron transfer kinetics, the increased electroactive surface area, the strong anti-interference capability, and excellent reproducibility and stability establish these modified electrodes as promising candidates for environmental monitoring and real sample analysis. Full article

Polylactic acid (PLA) is one of the most widely used materials for fused filament fabrication (FFF) or fused deposition modeling (FDM), being recognized for its low carbon footprint, relatively low costs and good mechanical properties. Improving the mechanical and technological properties of PLA with various additives has led to the production of different types of PLA-based filaments, such as hyper PLA (HPLA), PLA, PLA+ and PLA Lite. Studies on the mechanical properties of HPLA are scarce; therefore, the objective of this paper was to determine the mechanical properties of 3D-printed HPLA under tensile and bending stress conditions and to obtain numerical models that depend on the raster pattern orientation. The principal component analysis (PCA) reveals very different results for bending compared with tension, with outcomes varying significantly depending on the orientation of the raster angle. Full article

Background/Objectives: Dental implants are an established modality for oral rehabilitation, but their biomechanical success depends on controlling peri-implant strain, which is influenced by implant angulation, splinting, and length. This in vitro study evaluated the effects of these variables on strain and displacement under axial and oblique loading using digital image correlation (DIC). Methods: Three CBCT-derived mandibular models were 3D-printed and restored with screw-retained full-metal crowns. Group 1 compared parallel vs. angulated implants; Group 2 assessed splinted vs. non-splinted restorations; and Group 3 compared short (4.2 × 6.25 mm) vs. long (4.2 × 13 mm) implants. All specimens were loaded to 500 N at 0°, 15°, and 30° using a universal testing machine. Strain and displacement were analyzed with Istra 4D software and statistically evaluated using ANOVA and independent t-tests (α = 0.05). Results: Parallel implants exhibited progressively higher strain with load angle, peaking at 30° (p < 0.01), while angulated implants recorded their highest strain at 0° (p = 0.008), indicating better adaptation to oblique forces. Splinted restorations significantly reduced strain at 0° and 30° (p = 0.023) and lowered displacement across all inclinations (p = 0.0001). Short implants consistently produced greater strain and displacement than long implants (p < 0.02). Conclusions: Angulated implants mitigated strain under off-axis loading compared to parallel configurations. Splinting decreased strain and displacement, while longer implants consistently improved biomechanical performance. Optimal selection of implant orientation, splinting, and length may minimize peri-implant strain under functional loads. Findings are limited to in vitro conditions with static loading and a single implant system. Full article

In nature, structures such as earwig wings and mimosa leaves exhibit remarkable folding and unfolding capabilities. Inspired by these biological mechanisms, this work investigates soft foldable and torsional actuators based on Kresling crease pattern, fabricated using soft TPE 85A material through 3D printing. These actuators enable both foldable grasping and torsional motions. An analytical geometric model is developed to characterize the relationship between structural parameters and the inscribed circle area of a single-layer soft actuator, thereby elucidating their influence on contraction magnitude and relative deflection angle. Treating the soft actuator as an equivalent spring system, a mechanical model relating vacuum pressure to contraction ratio is further established, revealing an approximately linear relationship. The actuators are subsequently integrated with suction cups to form two end-effectors, a foldable soft gripper and a torsional soft gripper, and mounted onto a UR5 robotic arm via a customized flange. Demonstration experiments show that the foldable gripper achieves gentle, adaptive grasping of diverse objects, while the torsional gripper replicates human-like twisting motion, such as opening a bottle cap. This study highlights the potential of Kresling-based soft grippers for practical deployment in automated production tasks, including precision assembly and fruit harvesting. Full article

The textile industry is seeking alternative coloration methods to comply with the global demands for eco-friendly and non-hazardous dyes, as synthetic colorants are costly and substantially toxic in nature, having deleterious effects on the environment as well as ecosystems. This research aimed to develop a printed functional cotton fabric using a new bio-based pigment from acacia wood waste (Acacia nilotica) charcoal. Acacia charcoal was ground into fine powder and added into pigment paste with polyacrylic binder and screen printed on cotton fabric, followed by drying and curing. The printed fabric was tested for color strength (K/S), colorfastness, flame resistance, contact angle (for checking the hydrophobicity), thermal insulation, and tensile strength following standard testing protocols. Using different charcoal concentrations (in the range of 0.5–5%), the samples presented light to dark gray color and the K/S value gradually increased from 1.85 (0.5%) to 12.31 (5%), demonstrating stronger color depth. The printed fabrics revealed good results in terms of color fastness ratings (washing 3–5, dry rubbing 3–5, wet rubbing 3–5), satisfactory flame resistance, good thermal insulation, and excellent hydrophobicity. The obtained results contribute to sustainable and durable textile development for achieving better performance. Full article

Solar energy, as a clean and renewable resource, plays a pivotal role in advancing sustainable energy technologies. The efficiency of front-side silver paste is critical for the photovoltaic performance of Tunnel Oxide Passivated Contact (TOPCon) solar cells. In this study, we comprehensively investigated how the composition of organic vehicles in conductive pastes influences both printing rheological properties and electrical performance. Through rheological characterization, contact angle measurements, and Three-Interval Thixotropy Tests (3ITT), we examined the effects of varying solvent, binder, and thixotropic agent ratios on paste properties. The optimized formulation—a solvent mixture of lauryl alcohol ester (TE), butyl carbitol (DGME), butyl carbitol acetate (BCA), and dibutyl phthalate (DBP) in a 3:4:2:1 ratio, with ethyl cellulose (EC) STD10 as the binder and a polyamide wax (PAW)–hydrogenated castor oil (HCO) thixotropic agent at a 3:1 mass ratio—demonstrated superior viscosity control and rapid structural recovery. Printed grid lines achieved a height-to-width ratio (H/W) of 0.35 and a sheet resistance (Rs) of 1.43 Ω/□. These findings reveal direct relationships between organic vehicle composition, paste rheology, and functional performance, providing practical guidance for the design and optimization of high-performance conductive pastes for c-Si solar cells. This work establishes a foundation for improving both the efficiency and reliability of next-generation silver paste formulations in photovoltaic applications. Full article

The increasing adoption of digital light processing (DLP) three-dimensional (3D) printing in prosthodontics has enabled the rapid fabrication of denture bases with improved dimensional accuracy and reproducibility. However, the mechanical performance and surface characteristics of 3D-printed denture base resins remain inferior to those of conventional heat-polymerized polymethyl methacrylate (PMMA), limiting their long-term clinical reliability. This study aimed to investigate the effect of incorporating zinc oxide (ZnO) and samarium oxide (Sm₂O₃) nanoparticles, individually and as hybrid nanofiller systems, on the mechanical and wettability properties of a DLP 3D-printed denture base resin. ZnO and Sm₂O₃ nanoparticles were incorporated into a photopolymerizable denture base resin at concentrations of 1 and 2 wt.%, producing seven experimental formulations, including a control group. A total of 280 specimens were fabricated using a DLP 3D printer and subjected to standardized post-processing. Nanoparticle dispersion and morphology were examined using field-emission scanning electron microscopy (FE-SEM), while Fourier-transform infrared spectroscopy (FTIR) was employed to assess possible chemical interactions between the nanofillers and the polymer matrix. Mechanical performance was evaluated through impact strength, transverse strength, and flexural strength tests, and surface wettability was assessed using static water contact angle measurements. Statistical analysis was conducted using one-way ANOVA followed by Tukey’s post hoc test (α = 0.05). The results demonstrated that all nanoparticle-reinforced groups exhibited significantly enhanced mechanical properties compared with the unmodified control resin. The incorporation of 1 wt.% nanofillers yielded the most pronounced improvements, with the 1 wt.% ZnO group achieving the highest transverse strength and the 1 wt.% ZnO–Sm₂O₃ hybrid group exhibiting the maximum flexural strength. Increasing the nanofiller concentration to 2 wt.% resulted in partial reductions in impact and flexural strength, which were attributed to nanoparticle agglomeration and increased light scattering during photopolymerization. FTIR analysis revealed no evidence of chemical bonding between the resin matrix and the nanofillers, indicating that the observed enhancements were primarily governed by physical reinforcement mechanisms. Wettability analysis showed that Sm₂O₃-containing formulations significantly reduced the water contact angle, indicating increased surface hydrophilicity, whereas ZnO incorporation produced more hydrophobic surfaces. Within the limitations of this in vitro study, the findings suggest that low-concentration incorporation of ZnO and Sm₂O₃ nanoparticles represents an effective strategy to enhance the mechanical integrity and tailor the surface properties of DLP 3D-printed denture base resins. These results suggest potential clinical relevance of nanoparticle-reinforced printed denture bases, emphasizing the importance of optimized filler loading to avoid agglomeration-induced performance degradation. Full article

Objectives: To provide a mechanism-oriented integration of clinical and biomechanical evidence regarding fixation failure in fifth metatarsal fractures, with particular emphasis on Jones and diaphyseal stress fractures, and to clarify the mechanical determinants that influence construct performance under physiologic gait-related loading. Methods: A narrative, concept-driven review was conducted focusing on experimental biomechanical investigations and clinically relevant outcome studies addressing cyclic shear, bending, torsion, interfragmentary gap behavior, and loading direction. Special attention was given to studies employing advanced experimental models, including three-dimensional printed anatomical constructs combined with digital image correlation (DIC), to evaluate fixation strategies under simulated gait-phase loading conditions. Literature selection was guided by thematic relevance to construct mechanics and clinical fixation outcomes rather than systematic retrieval criteria. Results: Available evidence indicates that fixation constructs relying predominantly on interfragmentary compression demonstrate increased sensitivity to imperfect reduction, interfragmentary gaps, and multidirectional cyclic shear forces, particularly during midstance loading. Experimental models suggest that loading angle and gap size significantly influence stress concentration and failure patterns. Plate-based and hybrid constructs may provide improved resistance to cyclic bending and shear in specific experimental conditions, maintain stability in the presence of small fracture gaps, and distribute mechanical loads more uniformly across the fracture site. These biomechanical characteristics may help explain reported clinical patterns of delayed union, refracture, and hardware failure in high-demand patients or in cases with cortical compromise. Conclusions: Fixation failure in fifth metatarsal fractures appears to result from the interaction between fracture morphology, patient-specific loading demands, and construct biomechanics. Mechanism-based integration of biomechanical findings with clinical context may support individualized surgical decision-making. However, given the heterogeneity of available clinical data and the inherent limitations of experimental models, biomechanical insights should be interpreted as hypothesis-generating and complementary to clinical judgment rather than prescriptive guidance. Full article

This investigation focuses on rice husk biochar (RHBC) as a sustainable filler in a polylactic acid (PLA) matrix. This study employs optimization techniques, including central composite design (CCD) and analysis of variance (ANOVA), to systematically evaluate the effects of key 3D printing parameters such as filler content (0 wt.%, 10 wt.%, 20 wt.%), nozzle temperature (190 °C, 200 °C, 210 °C), orientation angle (0°, 60°, 120°), and fill pattern (hexagon, triangle, and 3D infill). Furthermore, machine learning models are used to predict the mechanical properties of PLA/RHBC composites from experimental data. The effects of these parameters on tensile strength, Young’s modulus, and hardness were analyzed. The ANOVA results showed that filler content was the most influential factor for tensile strength and Young’s modulus, contributing 36.47% and 73.25%, respectively, compared to pure PLA. For hardness, both filler content and nozzle temperature were key contributors, with a 44.08% improvement over pure PLA. Machine learning models, including multiple linear regression (MLR), K-Nearest Neighbors (KNN), Support Vector Machine (SVM), and Gradient Boosting, were used to predict the mechanical properties. Among these, Gradient Boosting achieved the best performance, with R² values of 97.79% for tensile strength, 98.79% for Young’s modulus, and 96.8% for hardness. This study provides a robust framework that combines experimental analysis, statistical design, and machine learning to optimize RHBC as an eco-friendly filler for the development of PLA composites for adoption in the automotive, sports and aerospace industries. Full article

To address the current research gap where studies on the failure mechanisms of fissured tunnels mainly focus on single tunnels with insufficient research on double tunnels, and to provide a scientific basis for disaster prevention and control of the Jinan Tunnel on Jinan Ring Expressway, this study investigates the mechanical behavior and failure characteristics of tunnel structures containing fissure–hole composite systems using experimental tests and numerical simulations. The crack initiation, propagation, and coalescence mechanisms are systematically analyzed to provide engineering references for tunnel design and stability assessment. Sand-based 3D printing technology was used to fabricate double-tunnel models with prefabricated fissures of different inclination angles α. Uniaxial compression tests were conducted, and crack evolution was monitored using DIC technology. Meanwhile, numerical simulation verification was performed based on the parallel bond (PB) model of the Discrete Element Method (PFC). The results show that the mechanical response of sand-based 3D-printed models conforms to the brittle characteristics of engineering rock masses. For models without fissures, cracks are preferentially initiated at the top and bottom of the tunnels. For models with fissures, the peak strength is the highest when α = 30° and 60°, and the lowest when α = 45° and 90°. As the fissure inclination angle increases, the tensile stress concentration shifts from the top and bottom of the tunnels and the middle of the fissure to the two ends of the fissure. The numerical simulation results are consistent with the experimental results and can accurately reproduce crack evolution. This study verifies the effectiveness of combining sand-based 3D printing with discrete element simulation, providing a reference for fissure prevention and control as well as operation and maintenance optimization of similar double-tunnel projects. Full article

Two approaches are described for construction of a screen-printed planar electrode (SPE) for potentiometric determination of iodide ion. The first, involves preparation and application of iron(II) bathophenanthroline tetraiodoplumbate complex ([Fe(bphen)₃][PbI₄]), as a sensitive and selective electroactive sensing material in a potentiometric electrode for iodide determination. The second is the use of a nano-sized poly(aniline-co-thiophene) (PANI-co-PT) as a solid-contact material in a planar miniaturized configuration. The SPE displays a Nernstian response for iodide ion with a calibration slope of −58.81 ± 0.69 mV/decade (R² = 0.9998) over a wide concentration range (9.17 × 10⁻⁷–6.94 × 10⁻³ mol/L), low detection limit (6.09 × 10⁻⁷ mol/L), rapid response time (5.0 ± 1.0 s) and long-life span (75 ± 3.0 d). The use of PANI-co-PT solid-contact layer significantly improves the ion-to-electron transduction, eliminates the formation of undesired thin water layer between the sensing membrane and the conducting substrate, prevents membrane delamination, enhances potential stability with a significantly reduced potential drift (8.32 ± 0.12 µV/min) and displays high redox capacitance (2.560 ± 0.040 mF). Water contact angle measurements confirm the increased hydrophobicity of the modified membrane electrode (from 44 ± 0.8° to 93 ± 1.4°) and demonstrate the membrane ability to repel moisture and further stabilize the sensor response. The proposed sensor is successfully integrated into a flow injection analysis (FIA) system to enable real-time and continuous iodide monitoring with high precision, high sample throughput and applicability for quality control of pharmaceuticals and environmental monitoring. Full article

We present an optical deformation sensor additively manufactured via an embedded printing process that enables the direct integration of colloidal quantum dots into multimode silicone (PDMS) waveguides. The sensor consists of two parallel waveguide strands, one of which is locally functionalized with CdSe/CdS quantum dots serving as fluorescent emitters. When narrow-band UV light at 405 nm is coupled into the non-functionalized strand, structural deformation alters the conditions of total internal reflection, thereby changing the optical interaction between both strands. This leads to a deformation-dependent variation in the fluorescence shift-affected intensity ratio, which serves as a self-referenced signal for angle determination. Using ratiometric evaluation, angular deflections of up to 9.5° are detected with a resolution below 1° ($2\sigma$ confidence), representing the performance of an initial functional prototype. The embedded printing process allows the voxel-wise adjustment of the material composition within a viscoplastic support medium and thus the spatially resolved integration of quantum dot-functionalized silicone. Attenuation losses of $0.81\pm 0.02\mathrm{dB}/\mathrm{cm}$ at 625 nm confirm the optical suitability of the printed waveguides. This approach combines optical sensing and structural flexibility within a single manufacturing step and establishes a pathway toward fully integratable deformation-sensing elements for soft robotic and wearable systems. Full article