Digital Processing Techniques Research Articles

Optimized DLP 3D-printed high-resolution nano zirconia-hydroxyapatite scaffold with craniomaxillofacial soft tissue invasion resistance and pro-osteogenic properties via dectin-1/syk inflammatory axis

One major challenge of craniomaxillofacial bone regeneration is the direct contact of subcutaneous fibrous tissue towards bone regenerative region, which results in fast fibroblast invasion and suppression of bone regeneration. Dectin-1, a pattern recognition receptor expressed on activated macrophages, is crucial for directing fibrous invasion. Targeting Dectin-1 and its downstream signaling cascade could be an effective strategy to resist “craniomaxillofacial soft tissue invasion”. Nano zirconia can shelter the essential amino acids of Dectin-1 and was reported to deactivate the inflammation signals. Herein, we succeeded in incorporating nano zirconia into high-resolution 3D hydroxyapatite (HA) scaffolds via modified digital light processing (DLP) technique system. The incorporation of nano zirconia can endow high-resolution HA scaffolds with the capacity of regulating the key structure of extracellular C-type lectin-like domain (CTLD) of dectin-1, proved by computational simulation. This results in inhibiting the dectin-1/syk axis and pro-soft tissue proliferation cytokines production. In vivo experiments further validated the effects of HA/nano zirconia resisting craniomaxillofacial soft tissue invasion and promoting bone regeneration. Our work practices the concept of “soft tissue invasion resisting capacity” via targeting in manipulating dectin-1, which succeeds in attenuating fibrous invasion and craniomaxillofacial bone regeneration. The “soft tissue invasion resisting capacity” could become a valuable biological paradigm of craniomaxillofacial bone biomaterials.

Polar-coordinate line-projection light-curing continuous 3D printing for tubular structures

3D printing techniques offer an effective method in fabricating complex radially multi-material structures. However, it is challenging for complex and delicate radially multi-material model geometries without supporting structures, such as tissue vessels and tubular graft, among others. In this work, we tackle these challenges by developing a polar digital light processing technique which uses a rod as the printing platform. The 3D model fabrication is accomplished through line projection. The rotation and translation of the rod are synchronized to project and illuminate the photosensitive material volume. By controlling the distance between the rod and the printing window, we achieved the printing of tubular structures with a minimum wall thickness as thin as 50 micrometers. By controlling the width of fine slits at the printing window, we achieved the printing of structures with a minimum feature size of 10 micrometers. Our process accomplished the fabrication of thin-walled tubular graft structure with a thickness of only 100 micrometers and lengths of several centimeters within a timeframe of just 100 s. Additionally, it enables the printing of axial multi-material structures, thereby achieving adjustable mechanical strength. This method is conducive to rapid customization of tubular grafts and the manufacturing of tubular components in fields such as dentistry, aerospace, and more.

Enhancing Mechanical and Thermal Properties of 3D-Printed Samples Using Mica-Epoxy Acrylate Resin Composites-Via Digital Light Processing (DLP).

Digital light processing (DLP) techniques are widely employed in various engineering and design fields, particularly additive manufacturing. Acrylate resins utilized in DLP processes are well known for their versatility, which enables the production of defect-free 3D-printed products with excellent mechanical properties. This study aims to improve the mechanical and thermal properties of 3D-printed samples by incorporating mica as an inorganic filler at different concentrations (5%, 10%, and 15%) and optimizing the dispersion by adding a KH570 silane coupling agent. In this study, mica was introduced as a filler and combined with epoxy acrylate resin to fabricate a 3D-printed sample. Varying concentrations of mica (5%, 10%, and 15% w/w) were mixed with the epoxy acrylate resin at a concentration of 10%, demonstrating a tensile strength increase of 85% and a flexural strength increase of 132%. Additionally, thermal characteristics were analyzed using thermogravimetric analysis (TGA), and successful morphological investigations were conducted using scanning electron microscopy (SEM). Digital light-processing technology was selected for its printing accuracy and cost-effectiveness. The results encompass comprehensive studies of the mechanical, thermal, and morphological aspects that contribute to the advancement of additive manufacturing technology.

Depth of reading within the gingival sulcus of seven intraoral scanners: an in vitro study.

The present in vitro study aimed to evaluate the depth of reading of intraoral scanners (IOSs) within the gingival sulcus. A knife-edge preparation for a full crown was performed on a Frasaco model. The gingival sulcus of the scanned model was modified using a dedicated software program (Model Creator, exocad DentalCAD 2.4 Plovdiv) by setting the apical width (AW), coronal width (CW), and gingival sulcus depth (D). Two dental models with different gingival sulcus depths (1 or 2 mm) were printed using the digital light processing (DLP) technique. Each model was scanned 10 times. Seven different IOSs were used: Emerald, Trios 3, Carestream 3600, Dental Wings DWIO, CondorScan, True Definition Scanner (TDS), and Cerec Omnicam. Measurements of D values were performed using 3Shape 3D viewer software. The normality of the data distribution was evaluated using the Shapiro-Wilk test (P < 0.05). The nonparametric Levene's test was used to check for homoscedasticity. The data were statistically analyzed using the Kruskal-Wallis test (α = 0.05) and the Nemenyi test. All IOSs were able to read within the 1-mm-deep gingival sulcus, albeit with some statistically significant differences (P < 0.001). TDS and Trios 3 were able to read within the 2-mm-deep gingival sulcus (P < 0.001). The depth of reading of different IOSs can vary significantly. In the model with a 2-mm gingival sulcus, even in the absence of oral fluids, the depth of reading was incomplete, suggesting that deep preparations into the gingival sulcus are difficult to detect with IOSs.

Imiquimod nanocrystal-loaded dissolving microneedles prepared by DLP printing.

The utilization of 3D printing- digital light processing (DLP) technique, for the direct fabrication of microneedles encounters the problem of drug solubility in printing resin, especially if it is predominantly composed of water. The possible solution how to ensure ideal belonging of drug and water-based printing resin is its pre-formulation in nanosuspension such as nanocrystals. This study investigates the feasibility of this approach on a resin containing nanocrystals of imiquimod (IMQ), an active used in (pre)cancerous skin conditions, well known for its problematic solubility and bioavailability. The resin blend of polyethylene glycol diacrylate and N-vinylpyrrolidone, and lithium phenyl-2,4,6-trimethylbenzoylphosphinate as a photoinitiator, was used, mixed with IMQ nanocrystals in water. The final microneedle-patches had 36 cylindrical microneedles arranged in a square grid, measuring approximately 600μm in height and 500μm in diameter. They contained 5wt% IMQ, which is equivalent to a commercially available cream. The homogeneity of IMQ distribution in the matrix was higher for nanocrystals compared to usual crystalline form. The release of IMQ from the patches was determined ex vivo in natural skin and revealed a 48% increase in efficacy for nanocrystal formulations compared to the crystalline form of IMQ.

Multi-round transmission and contention protocol in WLANs with multi-packet reception

Nowadays, there are many scenarios in Wi-Fi networks where many devices compete for network access via an Access Point to transmit their information. Thus, the ability to separate multiple packets sent simultaneously using advanced digital processing techniques in the physical layer, known as Multi-Packet Reception (MPR), has become crucial. As this feature may increase network throughput, medium access control (MAC) protocols that efficiently exploit the MPR capability have been investigated. This paper proposes a new MAC protocol that exploits the MPR capability in 802.11 RTS/CTS access mechanism networks. It is based on the use of multiple contention and transmission rounds. In this sense, the MPR MAC protocol schedules several transmission periods once the contention phase finishes. Multiple transmission rounds reduce the overhead and substantially increase throughput. The analytical expressions that support the proposed approach are derived and verified by simulation. The results show that the proposed MAC protocol can yield close to 94% of the ideal performance using only four transmission rounds, compared with 80% of the previous approaches in the literature.

Temporal analysis of the change in vegetation cover around the UHE Coaracy Nunes – Amapá

The construction of dams became necessary for national development, in wich the Amazon region, due to its great hydro-energy potential, became the country's hydroelectric frontier. The oldest region reservoir is the UHE Coaracy Nunes-Amapá, built in 1960 and operating since 1975. However, its construction generated several problems, such as loss of territoriality, difficulties in the subsistence of villages and modification of the environment. Therefore, understanding the changes that have occurred in the environment becomes relevant to knowledge, to enable recovery, preservation, conservation and local monitoring actions. In this way, the present study sought to understand if there were changes in the vegetation cover around the UHE Coaracy Nunes from 2000 to 2020. For this, remote sensing data were used. Eleven images obtained from the TM/Landsat-5, ETM+/Landsat 7 and OLI/Landsat-8 satellites were utilized, delimiting the study area with the creation of a polygon (buffer) around the UHE. Digital processing techniques were applied to these images with the support of pixel counting software. The Normalized Difference Vegetation Index (NDVI) was calculated, making it possible to obtain the median. The results obtained demonstrate that the image processing allowed to differentiate its constituent elements (plant cover, exposed soil and water body). The calculation of NDVI medians, for scenes between the years 2000 to 2020, ranged from 0,27 to 0,53 (mean of 0,43 ± 0,09), thus, the statistical analysis showed no relationship over the years (F1,9 = 2,31 and P = 0,16), indicating that during the analyzed period there were no changes in vegetation cover on the ground. This stability may be due to the stagnation of population growth in the city, as well as the presence of the Seringal Triunfo Natural Heritage Private Reserve within the selected area. Another factor that can be attributed to this stability is the pixel count, as the surface of water bodies was not removed. However, the use of Landast satellite images, temporal sequence and the NDVI index proved to be effective tools in remote sensing, enabling the understanding of the dynamics of vegetation cover around the UHE Coaracy Nunes, thus showing its stability in the analyzed period.

Development of hybrid 3D printing approach for fabrication of high-strength hydroxyapatite bioscaffold using FDM and DLP techniques

This study develops a hybrid 3D printing approach that combines fused deposition modeling (FDM) and digital light processing (DLP) techniques for fabricating bioscaffolds, enabling rapid mass production. The FDM technique fabricates outer molds, while DLP prints struts for creating penetrating channels. By combining these components, hydroxyapatite (HA) bioscaffolds with different channel sizes (600, 800, and 1000 μm) and designed porosities (10%, 12.5%, and 15%) are fabricated using the slurry casting method with centrifugal vacuum defoaming for significant densification. This innovative method produces high-strength bioscaffolds with an overall porosity of 32%–37%, featuring tightly bound HA grains and a layered surface structure, resulting in remarkable cell viability and adhesion, along with minimal degradation rates and superior calcium phosphate deposition. The HA scaffolds show hardness ranging from 1.43 to 1.87 GPa, with increasing compressive strength as the designed porosity and channel size decrease. Compared to human cancellous bone at a similar porosity range of 30%–40%, exhibiting compressive strengths of 13–70 MPa and moduli of 0.8–8 GPa, the HA scaffolds demonstrate robust strengths ranging from 40 to 73 MPa, paired with lower moduli of 0.7–1.23 GPa. These attributes make them well-suited for cancellous bone repair, effectively mitigating issues like stress shielding and bone atrophy.

Digital light processing technique aided 3D printing hierarchical super-wetting mesh coated with hydrophobic SiO2 for highly efficient oil-water separation

Gravity-driven filtration using super-wetting mesh surfaces holds significant promise in addressing oil pollution resulting from human activities. However, conventional techniques need help fabricating efficient separation mesh structures due to their limited stability in oily-water solutions. To overcome this, we employed a Digital Light Processing (DLP) 3D printing technique to fabricate a mesh with a micro-patterned surface using a UV light-curable polyurethane (PU). A post-UV curing step was implemented to transform the soft segments of PU into a solid state. To enhance the super-wetting properties, hydrophobic modified silica (m-SiO2)/UV curable polydimethylsiloxane (PDMS) solution was applied through dip coating, resulting in a hierarchical structure with high surface roughness and superhydrophobic characteristics. In oil–water separation tests, the hierarchical superhydrophobic mesh, featuring a pore size of 300 µm, demonstrated exceptional performance, achieving a remarkable flow flux of 37,410 L/m2 h with a separation efficiency of 97.46 %. Furthermore, the separation efficiency remained consistently above 97.0 % under varying pH conditions and oil mixtures, highlighting the excellent water-repellence capacity of the hierarchical mesh developed in this study.

Harnessing disulfide and transesterification bond exchange reactions for recyclable and reprocessable 3D-printed vitrimers

Two new vitrimeric materials have been studied for potential additive manufacturing applications such as 3D-printing. A monomer containing disulfide bonds and β-hydroxyesters was easily synthesized from two low-cost and commercially available reagents. Another disulfide-containing monomer was synthesized for comparison purposes. Materials were prepared through a UV-light radical polymerization of methacrylates. The addition of two reactive diluents such as poly(ethylene glycol) methyl ether methacrylate (PEGMA) and ethylene glycol phenyl ether methacrylate (EGPMA) was necessary to achieve a suitable viscosity for the curing as well as for their printability. The curing process was controlled by FTIR. Thermomechanical properties were investigated by means of DMTA analysis revealing near-ambient Tg values. Stress relaxation tests revealed that both materials were capable to relax the 63% of the initial stress in less than 10 min at 110 °C. The recyclability of the materials was achieved, and the mechanical and thermomechanical properties of the recycled samples were compared to the virgin ones revealing a great recovery of the initial properties. Finally, Digital Light Processing (DLP) technique was used to print complex structures with high resolution highlighting the great potential of these vitrimeric materials in 3D printing.

Nanomaterial-Coated Carbon-Fiber-Based Multicontact Array Sensors for In Vitro Monitoring of Serotonin Levels.

In this study, we demonstrated the fabrication of multicontact hierarchical probes for the in vitro detection of serotonin levels. The basic three-dimensional (3D) bendable prototypes with 3 (C1), 6 (C2), or 9 (C3) contact surfaces were printed from polymeric resin via the digital light processing (DLP) technique. We chose ultrasonicated carbon fiber strands to transform these designs into multicontact carbon fiber electrodes (MCCFEs). The exposed carbon fiber (CF) surfaces were modified with aminopropyl alkoxysilane (APTMS), followed by the subsequent loading of palladium nanoclusters (PdNPs) to build active recording sites. CF functionalization with PdNPs was achieved by the wet chemical reduction of Pd(II) to Pd(0). The MCCFE configurations demonstrated an enhancement in the electroactive surface area and an improved voltammetric response toward 5-HT oxidation by increasing the points of the contacts (i.e., from C1 to C3). These MCCFEs are comparable to 3D-protruding electrodes as they can enable multipoint analyte detection. Along with the electrode patterns, morphological irregularities associated with both Pd-doped and undoped CFs supported the creation of proximal diffusion layers for facile mass transfer. Low detection limits of 0.8-10 nM over a wide concentration range, from 0.005 nM to 1 mM, were demonstrated. The MCCFE sensors had a relatively low standard deviation value of ∼2%. This type of sensitive and cost-effective electrochemical sensor may prove useful for collecting electrical impulses and long-term monitoring of 5-HT in vivo in addition to in vitro testing.

Experimental surface runoff hydrographs from linear impervious subcatchments for rainfalls of extremely high intensity

This study focuses on lab-scale experimental runoff hydrographs from a linear completely impervious plane subcatchment. An improved method of surface runoff physical modelling was developed, allowing for expanded laboratory hydrograph simulations up to a linear scale of 10. Model rains of different intensities and durations were applied, and digital online data processing techniques were employed to ensure high time resolution and accurate flow rate determination. The experimental hydrographs were analyzed in a dimensionless form to facilitate generalization and comparison with widely used nonlinear reservoir method and unit hydrograph method. Wave-like fluctuations of the flow rate were observed in most experimental hydrographs as they approached the maximum runoff. The dimensionless phase time of the experimental hydrographs showed an increasing trend with higher rainfall intensity, and a power-law equation was derived to approximate this relationship. An averaged dimensionless runoff hydrograph was obtained by processing individual hydrographs, and it was approximated by the DR-Hill-Zerobackground model for the initial stage during the rainfall and by the Weibull model for the later stage, after the rainfall stopped. The findings of this study have significant implications for modelling surface runoff from small urban subcatchments, particularly under critical rainfall events with extremely high intensity.

Optimizing Surface Finish and Dimensional Accuracy in 3D Printed Free-Form Objects

3D printing of free-form objects presents inherent complexity due to their organic and intricate shapes. Designers engage with such objects, considering a range of factors including aesthetics, engineering viability, and ergonomic comfort. This research is focused on achieving the most effective printing parameters for a free-form object utilizing the Digital Light Processing (DLP) technique within a 3D printer. Within this study, a squeezed hexagonal tube-shaped CAD model was employed as an experimental subject, following the principles of the Response Surface Method (RSM). The research delved into the optimization of printing parameters, particularly layer thickness and exposure time, to enhance the dimensional accuracy and surface quality of the free-form model. Two levels were established for each factor: layer thickness was set at 0.06 mm (low) and 0.08 mm (high), while exposure time was tested at 6 s (low) and 8 s (high). The assessment of surface quality involved a qualitative evaluation employing a digital microscope to identify potential defects and imperfections in the print outcomes. The investigation culminated in the identification of the optimal printing parameters: a layer thickness of 0.0753 mm and an exposure time of 7.2143 seconds. This achievement not only enhances the understanding of 3D printing variables in the context of intricate free-form models but also contributes to the broader field of additive manufacturing parameter optimization.

Enhancing compressive performance in 3D printed pyramidal lattice structures with geometrically tailored I-shaped struts

This study examines the compressive response of geometrically tailored pyramidal lattice structures composed of struts with I-shaped cross-sections. Geometrically tailored pyramidal lattices with micro-scale features are 3D printed using the Digital Light Processing (DLP) technique, and their effective elastic modulus, collapse strength and energy absorption capacity are experimentally evaluated under quasi-static compressive loading. Furthermore, detailed non-linear finite element (FE) calculations are performed to examine underlying collapse mechanisms and explore the vast design space offered by the proposed geometrical tailoring scheme. Both the experimental and numerical results show that the geometrically tailored lattice structures outperform conventional pyramidal lattices of equal weight in terms of elastic modulus (+24 %), collapse strength (+21 %) and energy absorption (+68 %). Notably, these strength improvements are attributed to lateral buckling that prompts the I-shaped struts to bend sideways during collapse. Specific cross-sectional designs demonstrate remarkable enhancements in strength and energy absorption, reaching up to 93 % and 161 %, respectively, differentiating them significantly from conventional designs.

Three-Dimensional Printing of Triboelectric Nanogenerators by Digital Light Processing Technique for Mechanical Energy Harvesting.

Triboelectric nanogenerators (TENGs) represent intriguing technology to harvest human mechanical movements for powering wearable and portable electronics. Differently, compared to conventional fabrication approaches, additive manufacturing can allow the fabrication of TENGs with good dimensional resolution, high reproducibility, and quick production processes and, in particular, the obtainment of complex and customized structures. Among 3D printing technologies, digital light processing (DLP) is well-known for being the most flexible to produce functional devices by controlling both the geometry and the different ingredients of printable resins. On the other hand, DLP was not exploited for TENG fabrication, and consequently, the knowledge of the performance of 3D printable materials as charge accumulators upon friction is limited. Here, the application of the DLP technique to the 3D printing of triboelectric nanogenerators is studied. First, several printable materials have been tested as triboelectric layers to define a triboelectric series of DLP 3D printable materials. Then, TENG devices with increased geometrical complexity were printed, showcasing the ability to harvest energy from human movement. The method presented in this work illustrates how the DLP may represent a valuable and flexible solution to fabricate triboelectric nanogenerators, also providing a triboelectric classification of the most common photocurable resins.

Delamination mitigation in additively manufactured Al2O3 via enhanced thermal postprocessing

AbstractManufacturing thick (&gt;10 mm) alumina (Al2O3) parts through the ceramic additive manufacturing technique of digital light processing (DLP) is difficult due to the large amount of polymer that must be removed. Nearly 35–65 vol% of a fugitive UV‐curable polymer is used in commercial ceramic slurries in order to maintain shape through the DLP process. During the thermal debind, gases form and escape quickly due to pressure build‐up, leading to defects in the form of print layer delamination. Here, we analyze the polymer decomposition through thermogravimetric analysis in order to design a less aggressive thermal debind schedule through strategic thermal holds and decreased heating rates. The new schedule led to a 83% reduction in average delaminations per sample (from 6.9 delaminations per sample to 1.2 delaminations per sample) and up to a 100% increase in wall thickness (from nominally 10–20 mm). A complex, Al2O3 turbine rotor (with maximum wall thickness of 5 mm in the center hub section) of a JetCat P400 engine was fabricated to compare the new schedule to the manufacturer provided one. The improved thermal debind schedule produced a turbine rotor with no observable delamination defects.

Results of capillary studies digital processing and interpretation with the aim of a pore channel size distribution function constructing

Pore channels distribution in reservoir by size largely determines such filtration parameters as absolute and phase permeability, as well as the residual oil saturation of the productive reservoir. This paper presents a technique for capillary research data digital processing in order to obtain a function graph of reservoir pore channels by size distribution. In this case, a generalized mathematical model of capillary pressure curves is used. The generalized model makes it possible to increase the accuracy of capillary curves approximation in the medium and small pore channels area. In this regard, the proposed digital processing technique makes it possible to increase the accuracy and efficiency of constructing the pore channel size distribution function. Keywords: pore channels; distribution density; permeability; oil saturation; digital processing technique.

4D-Printable Photocrosslinkable Polyurethane-Based Inks for Tissue Scaffold and Actuator Applications.

4D printing recently emerges as an exciting evolution of conventional 3D printing, where a printed construct can quickly transform in response to a specific stimulus to switch between a temporary variable state and an original state. In this work, a photocrosslinkable polyethylene-glycol polyurethane ink is synthesized for light-assisted 4D printing of smart materials. The molecular weight distribution of the ink monomers is tunable by adjusting the copolymerization reaction time. Digital light processing (DLP) technique is used to program a differential swelling response in the printed constructs after humidity variation. Bioactive microparticles are embedded into the ink and the improvement of biocompatibility of the printed constructs is demonstrated for tissue engineering applications. Cell studies reveal above 90% viability in 1 week and ≈50% biodegradability after 4 weeks. Self-folding capillary scaffolds, dynamic grippers, and film actuators are made and activated in a humid environment. The approach offers a versatile platform for the fabrication of complex constructs. The ink can be used in tissue engineering and actuator applications, making the ink a promising avenue for future research.

Obtaining biocompatible polymeric scaffolds loaded with calcium phosphates through the digital light processing technique

AbstractIn the present work, scaffolds with gyroid TPMS geometry were obtained from a commercial resin of acrylic nature loaded with 0.5% and 1% w/V of calcium phosphate nanoparticles through DLP. The scaffolds obtained presented Young's Modulus between 300 and 400 MPa, which makes them suitable for bone applications. The surface treatment by oxygen plasma carried out on the scaffolds resulted in a notable improvement in the wettability of the surfaces, which favours cell adhesion on the surface of the materials. The in vitro bioactivity assay conducted on the resin/calcium phosphate particles composite material showed that an apatitic layer forms on the surface of the samples from the third day of exposure to simulated body fluid (SBF), indicating that the composite material has in vitro bioactive behaviour. Biological tests demonstrated that the material is not cytotoxic and favours cell adhesion and that the gyroid geometry promotes cell proliferation. Graphical abstract

Experimental and numerical investigation on 2.5-dimensional nature-inspired infill structures under out-plane quasi-static loading

The 2.5-dimensional (2.5D) infill structures are gaining more attention due to their better energy absorption capabilities and lightweight. The additive manufacturing eases the fabrication of these structures and made them accessible for industrial and transport applications. The present work is focused on enhancing energy absorption capability, and mean crush force (MCF) for a novel nature-inspired 2.5D infilled structure through nature-inspired 2.5D geometries. Six nature-inspired geometries are considered for a comparative analysis with the proposed novel snowflake-inspired 2.5D infilled structure to sustain under quasi-static out-plane loading. These structures are cylindrical shells filled with different infill configurations and maintained at constant volume. The structures are fabricated using three-dimensional printing through the digital light processing technique with photopolymer resin and tested under compressive out-plane quasi-static loading conditions. Numerical simulations were performed by ANSYS and compared with experimental results to corroborate the reliability. The effect of infill configurations and supported ribs on the crushing behaviour is discussed in detail. The results reveal a significant improvement in MCF, specific energy absorption, and confined crushing deformation for the proposed lightweight 2.5D infill structures.