Digital Light Processing Printing Research Articles

Advancements in DLP 3D printing: High strength alumina toughened zirconia ceramics for biomedical applications

Digital Light Processing (DLP) enables intricate ceramic part production from photosensitive ceramic slurry. While ZrO2 and Al2O3 are commonly studied, their composites are underexplored despite diverse applications. This study investigates fabricating high-strength, fully dense alumina-toughened zirconia (ATZ) parts using a low-cost desktop DLP printer designed for polymer printing. Various ATZ-based ceramic slurries (30, 35, 42.5 vol%) with different binders and dispersants were prepared and evaluated for curing and rheological properties. Promising formulations underwent debinding and sintering, resulting in homogenous microstructures with a well-distributed blend of the two phases. For the doped samples, SEM analysis revealed a good distribution of dopants and elongated dopant grains infused at higher temperatures. The 35 vol% ATZ exhibited exceptional average flexural strength of 1321 MPa, surpassing previous DLP-fabricated composites. This suggests no need for increased solid loading content. The findings demonstrate the potential of DLP in producing high-performance ceramic parts with tailored properties.

Digital light processing printing of porous ceramics using interparticle photo-cross-linkable Pickering emulsions

Digital light processing (DLP) printing using photo-curable Pickering emulsion is a promising route to fabricate porous ceramics having on-demand structures. However, the long duration for debinding/sintering due to the large organic contents remained in the photo-cured bodies and the insufficient long-term stability of the emulsions needs to be solved toward efficient manufacturing. Herein, a new interparticle photo-cross-linkable Pickering emulsion having improved stability, which can be photo-cured using reduced amounts of monomers, were designed for the rapid production of porous ceramics using DLP printing. The Pickering emulsion was obtained by mixing isopropyl myristate into a dimethyl sulfoxide (DMSO) aqueous suspension of SiO2 particles with pre-dissolved polyethylene glycol diacrylate (PEGDA) and a photo-radical initiator. Further, functionalized polyethyleneimine (PEI) was designed to ensure the dispersion of SiO2 particles and formation of a Pickering emulsion. The photo-irradiation of the designed Pickering emulsion resulted in the successful photo-curing by the radical polymerization of PEGDA, followed by a Michael addition reaction between the reactive amine of PEI and acryloyl groups of PEGDA. The improved stability of the emulsion over time and reduced amounts of monomer facilitated the application of the designed emulsion to DLP printing, followed by a rapid firing process without any structural collapse.

3D DLP-printed cannabinoid microneedles patch and its pharmacokinetic evaluation in rats.

The objective of the present study was to enhance the bioavailability of cannabidiol (CBD) using 3D Digital Light Processing (DLP)-printed microneedle (MN) transdermal drug delivery system. CBD MN patch was fabricated and optimized using 3D DLP printing using CBD (8% w/v), Lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) (0.49% w/v), distilled water (20% w/v), and poly (ethylene glycol) dimethacrylate 550 (PEGDAMA 550) (up to 100% w/v). CBD MNs were characterized for their morphology, mechanical strength, in vitro release study, ex vivo permeation study, and in vivo pharmacokinetic (PK) profile. Microscopic images showed that sharp CBD MNs with a height of ~800 μm, base diameter of ~250 μm, and tip with a radius of curvature (RoC) of ~15 μm were successfully printed using optimized printing parameters. Mechanical strength studies showed no significant deformation in the morphology of CBD MNs even after applying 0.5N/needle force. Ex vivo permeation study showed significant (P < .0001) permeation of CBD in the receiving media as compared to CBD patch (control). In vivo PK study showed significantly (P < .05) enhanced bioavailability in the case of CBD MN patch as compared to CBD subcutaneous inj. (control). Overall, systemic absorption of CBD was significantly enhanced using 3D-printed MN drug delivery system.

3D bioprinting of stromal cells-laden artificial cornea based on visible light-crosslinkable bioinks forming multilength networks

3D bioprinting has the potential for the rapid and precise engineering of hydrogel constructs that can mimic the structural and optical complexity of a healthy cornea. However, the use of existing light-activated bioinks for corneal printing is limited by their poor cytocompatibility, use of cytotoxic photoinitiators (PIs), low photo-crosslinking efficiency, and opaque/colored surface of the printed material. Herein, we report a fast-curable, non-cytotoxic, optically transparent bioprinting system using a new water-soluble benzoyl phosphinate-based PI and photocrosslinkable methacrylated hyaluronic acid (HAMA). Compared with commercially available PIs, the newly developed PI, lithium benzoyl (phenyl) phosphinate (BP), demonstrated increased photoinitiation efficiency under visible light and low cytotoxicity. Using a catalytic amount of BP, the HA-based bioinks quickly formed 3D hydrogel constructs under low-energy visible-light irradiation (405 nm, <1 J cm−2). The mechanical properties and printability of photocurable bioinks were further improved by blending low (10 kDa) and high (100 kDa) molecular weight (MW) HAMA by forming multilength networks. For potential applications as corneal scaffolds, stromal cell-laden dome-shaped constructs were fabricated using MW-blended HAMA/BP bioink and a digital light processing printer. The HA-based photocurable bioinks exhibited good cytocompatibility (80%–95%), fast curing kinetics (<5 s), and excellent optical transparency (>90% in the visible range), potentially making them suitable for corneal tissue engineering.

Additive manufacturing of yttria-stabilized zirconia using digital light processing: Green density and surface roughness analysis

The amalgamation of digital light processing (DLP) technology and pressureless sintering has emerged as a promising method for producing delicate, complex, and custom-made yttria-stabilized zirconia (YSZ) components. The procedure consists of fabrication of green part using DLP, debinding to remove the binders and sintering to densify the parts. Explorations in the parameter selection in each step are still far from maturity for producing defect-free densified parts. This study addresses the effect of DLP print parameters on the density of green parts and surface irregularities. DLP printing parameters, such as layer thickness, orientation, and light intensity, were selected, and a central composite design methodology was adopted for the design of experiments to investigate the impact of individual parameter as well as their interactions. The density of the green part decreased with an increase in layer thickness from 10 μm to 70 μm, whereas an increase in density was observed when the part orientation changed from 0 ° to 90°, and the intensity changed from 10 to 50 mW/cm2. The variations in layer thickness and part orientation substantially impact the surface roughness, but variations in intensity have comparatively less influence on the surface roughness. The in-layer and inter-layer voids of the samples fabricated with varying parameters were analyzed using scanning electron microscopy. The minimum surface roughness and maximum green part density responses were obtained using regression equations and a multi-objective optimization strategy. Subsequently, the samples were debinded and sintered to produce high-density zirconia components. To establish the importance of parameter optimization, a comparison of the specimen density and surface irregularity in the green and sintered states was performed for specimens fabricated with optimized parameters and a randomly chosen set of parameters. The novel study provides the parametric relation to fabricate as desired green and sintered density parts along with tuned surface roughness.

Digital light processing-based bioprinting of microtissue hydrogel arrays using dextran-induced aqueous emulsion ink

As a microscale three-dimensional bionic model, a microtissue array is a promising method for disease modeling and drug screening. Digital light processing (DLP) 3D bio-printing technology with the capabilities of excellent printing speed and resolution shows great potential for fabricating microtissue arrays. However, the outcomes of the microtissue arrays using DLP are limited by the shortage of biomaterials. In this work, we prepare hydrogel microtissues by combining DLP printing technology with biphasic bio-ink consisting of gelatin methacrylate (GelMA) and dextran. GelMA/ dextran is mixed to form bio-inks with different volume ratios, which can achieve high-precision printing of various patterns. Due to the presence of dextran, the bio-inks form the internal porous structure of the hydrogel in the printed patterns. The pore size is related to the proportion of dextran in bio-inks, and the pore size of hydrogel becomes smaller with the increase of dextran ratio. In addition, the adipose-derived stem cells (ADSCs) cells encapsulated in the porous hydrogels can maintain a high survival rate of 98.01% after 3 days of culture, and the larger pore size in the hydrogels promotes cell migration. Combining the DLP printing system with the porous hydrogel allows multiple micro-size geometric pattern hydrogels to be printed simultaneously to form microtissue arrays. In this study, a new bio-ink suitable for microtissue arrays is proposed, and a simple, accurate, and high-throughput biological manufacturing method for microtissue arrays is developed, thus providing a valuable tool for drug screening and tissue engineering.

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.

Experimental investigation and optimization of process parameters on digital light processing (DLP) 3D printing process based on Taguchi-grey relational analysis

Additive manufacturing technology, specifically Digital Light Processing (DLP), offers a unique approach to fabricating intricate objects without the need for traditional molds or machining. The technique described entails the incremental construction of layers through the curing process polymer, facilitated by a projection light source. Digital Light Processing 3D printing is particularly suited for creating complex structures with small cross-sections, requiring high surface polish and durability. In this study, DLP-printed test coupons were produced using an Ultraviolet-sensitive resin, and the investigation focused on examining the impact of surface quality and toughness, adhering to guidelines outlined by the ASTM specifications. To optimize the DLP printing process, Taguchi and Grey relational optimization techniques were employed to find the best values for multiple factors. The parameters considered in this study were speed, layer thickness, orientation, and pattern type. By employing these techniques, the optimal parameters were identified as follows: The printing process is conducted at a speed of 3 mm per second, with each layer being 0.05 mm thick and the orientation of the printed object is set at 90 degrees, and the pattern employed is of the square type. Experimental results revealed that utilizing these parameters yielded a surface roughness of 2.58 µm and an impact strength of 9.1J. The results showed that the Grey relational grade improved from 0.6244 to 0.7974, with a deviation of 0.173 and 27.71%, indicating a significant enhancement in the optimization process. Additionally, contour plots depicting the relationships between speed and orientation, speed and layer thickness, and orientation and layer thickness were generated for surface roughness, impact strength, and the Grey relational grade. This research offers valuable insights into optimizing DLP 3D printing processes to achieve enhanced surface quality, toughness, and material efficiency while reducing costs and production time.

3D printing of high solid Al2O3 ceramics based on green and renewable photosensitive resin with low viscosity and low shrinkage

AbstractA low‐viscosity bio‐based carbamate acrylate was synthesized by the reaction of pentamethylene diisocyanate derived from pentanediamine with a low molecular weight acrylate hydroxyl ester. The carbamate acrylate was used in the 3D printing of ceramics, and a correlation between the solid content and viscosity of the ceramic slurry was observed. The ceramic slurry exhibits good stability and low shrinkage. The results indicate that the viscosity of the ceramic slurry was 2.11 Pa s with a solid content of 80 wt%, which makes it suitable for digital light processing printing. In addition, a new type of photoinitiator called (2,4,6‐trimethylbenzoyl)bis(p‐tolyl)phosphine oxide (TMO) has been applied, demonstrating excellent potential in ceramic slurry. According to its thermogravimetric curve, a debinding and sintering process was designed, and ultimately an Al2O3 device with a density of 94.49% was prepared.

High-precision digital light processing (DLP) printing of microstructures for microfluidics applications based on a machine learning approach

ABSTRACT Digital light processing (DLP) is renowned for its precision, but the challenge lies in the identification of optimal print parameters to minimise print errors and enhance overall print accuracy. This study introduces a groundbreaking approach by integrating 'Random Forest' (RF) models with DLP printing to construct a predictive model for printing errors to achieve unparalleled precision. We conducted experiments using common commercial resins to print, resulting in a comprehensive dataset of 690 experimental datasets. Consequently, we validated this approach by fabricating Y-type microfluidic structures with a minimum feature size printing of 2 µm and herringbone mixer structures with feature sizes of 21.2 µm. We successfully controlled the average print error below 2.3 µm. The 'RF' model was also extended from the printing of microfluidics (2.5D) to complex spatial three-dimensional (3D) Triple-Periodic Minimal Surface (TPMS) structures. We have successfully achieved the printing of TPMS-Gyroid and TPMS-Diamond structures with a minimum feature size of 20 µm, while the printing errors were all kept within 1.5 µm. This study underscores the generalizability and immense potential of integrating machine learning techniques with high-precision DLP printing, offering valuable insights for future research in the realm of high-precision and expeditious 3D printing.

Trueness of five different 3D printing systems including budget- and professional-grade printers: An In vitro study

ProblemSeveral types of 3D printers with different techniques and prices are available on the market. However, results in the literature are inconsistent, and there is no comprehensive agreement on the accuracy of 3D printers of different price categories for dental applications. AimThis study aimed to investigate the accuracy of five different 3D printing systems, including a comparison of budget- and higher-end 3D printing systems, according to a standardized production and evaluation protocol. Material and methodsA maxillary reference model with prepared teeth was created using 16 half-ball markers with a diameter of 1 mm to facilitate measurements. A reference file was fabricated using five different 3D printers. The printed models were scanned and superimposed onto the original standard tesselation language (.stl) file, and digital measurements were performed to assess the 3-dimensional and linear deviations between the reference and test models. ResultsAfter examining the entire surface of the models, we found that 3D printers using Fused filament fabrication (FFF) technology −120.2 (20.3) μm create models with high trueness but high distortion. Distortions along the z-axis were found to be the highest with the stereolithography (SLA)-type 3D printer at −153.7 (38.7) μm. For the 4-unit FPD, we found 201.9 (41.8) μm deviation with the digital light processing (DLP) printer. The largest deviation (−265.1 (55.4) μm) between the second molars was observed for the DLP printer. Between the incisor and the second molar, the best results were produced by the FFF printer with −30.5 (76.7) μm. ConclusionBudget-friendly 3D printers are comparable to professional-grade printers in terms of precision. In general, the cost of a printing system is not a reliable indicator of its level of accuracy.

Development of stretchable microneedle arrays via single-step digital light-processing printing for delivery of rhodamine B into skin tissue

This paper introduces a novel approach for loading and releasing Rhodamine B (RhB) into the skin using minimally-invasive microneedle technology developed through digital light-processing (DLP) printing. Notably, this process involves the direct 3D fabrication of rigid microneedle arrays affixed to a flexible patch, marking a pioneering application of DLP printing in this context. The stretchable and durable design of the microneedle substrate enables it to adapt to dynamic movements associated with human activities. Moreover, the microneedle features a pore on each side of the pyramid needle, effectively optimizing its drug-loading capabilities. Results indicate that the microneedle patch can withstand up to 50 % strain without failure and successfully penetrates rat skin. In vitro drug release profiles, conducted through artificial and rat skin, were observed over a 70 h period. This study establishes the potential of a simple manufacturing process for the creation of pore-designed microneedle arrays with a stretchable substrate, showcasing their viability in transdermal drug delivery applications.

Chemical Circularity in 3D Printing with Biobased Δ-Valerolactone.

Digital Light Processing (DLP) is a vat photopolymerization-based 3D printing technology that fabricates parts typically made of chemically crosslinked polymers. The rapidly growing DLP market has an increasing demand for polymer raw materials, along with growing environmental concerns. Therefore, circular DLP printing with a closed-loop recyclable ink is of great importance for sustainability. The low-ceiling temperature alkyl-substituted δ-valerolactone (VL) is an industrially accessible biorenewable feedstock for developing recyclable polymers. In this work, acrylate-functionalized poly(δ-valerolactone) (PVLA), synthesized through the ring-opening transesterification polymerization of VL, is used as a platform photoprecursor to improve the chemical circularity in DLP printing. A small portion of photocurable reactive diluent (RD) turns the unprintable PVLA into DLP printable ink. Various photocurable monomers can serve as RDs to modulate the properties of printed structures for applications like sacrificial molds, soft actuators, sensors, etc. The intrinsic depolymerizability of PVLA is well preserved, regardless of whether the printed polymer is a thermoplastic or thermoset. The recovery yield of virgin quality VL monomer is 93% through direct bulk thermolysis of the printed structures. This work proposes the utilization of depolymerizable photoprecursors and highlights the feasibility of biorenewable VL as a versatile material platform toward circular DLP printing.

Build angle effect on 3D-printed dental crowns marginal fit using digital light-processing and stereo-lithography technology: an in vitro study

BackgroundThe effect of 3D printing technology and build angle on the marginal fit of printed crowns is unclear. The objective of this research was to use digital light processing (DLP) and stereo-lithography (SLA)-based 3D printing to construct single restorations with varied build angles and to analyze the crowns′ marginal fit.MethodsA prepared resin first molar was scanned utilizing an optical scanner. Three build orientations were used to construct the specimens: 0, 45, and 90º. DLP and SLA technology were used to produce the casting patterns. A digital microscope was used to measure the marginal gaps. The effect of build orientation was statistically analyzed by using Two-way ANOVA followed by pair-wise Tukey test.ResultsTwo-way ANOVA revealed a significant effect of printer technology and build angle on the marginal discrepancy of 3D printed crowns (p < 0.001). One-way ANOVA revealed that SLA printers (55.6 [± 13.59]) showed significantly better mean [± SD] marginal discrepancy in µm than DLP printers (72 [± 13.67]) (p < 0.001). Regarding build angle, one-way ANOVA revealed significant differences between the different angles. Tukeys post-hoc test revealed that 0° (48.5 [± 9.04]) had the significantly smallest marginal discrepancy followed by 45° (62.5 [± 8.05]) then 90° (80.5 [± 8.99]) (p < 0.001).ConclusionThe build orientation affects the marginal discrepancy of single crowns manufactured utilizing DLP and SLA.

Accuracy of zirconia crown manufactured using stereolithography and digital light processing

ObjectivesThe aim of this study is to evaluate the accuracy of zirconia crowns fabricated using stereolithography (SLA) and digital light processing (DLP) and to compare their accuracy with those fabricated using the subtractive manufacturing (SM) method. MethodsA typodont model with a prepared maxillary first molar was scanned, and the anatomical contour crown was designed using dental computer-aided-design (CAD) software. The designed file in standard tessellation language (STL) format was used to fabricate 10 crowns per group. The crowns were manufactured using a dental milling machine (Datron D5; MLC group), SLA (CERAMAKER 900; SLAC group), and DLP (ZIPRO; DLPC group) printers. The fabricated crowns were scanned using a dental laboratory scanner and saved in three parts: the external, intaglio, and marginal surfaces. For accuracy assessment, these parts were superimposed to the reference file. Root mean square (RMS) values were evaluated using three-dimensional analysis software (Geomagic Control X). Statistical significance was evaluated using a nonparametric Kruskal–Wallis test (α = 0.05) and a post-hoc Mann–Whitney U test with Bonferroni correction (α = 0.016). ResultsTrueness evaluation revealed the lowest RMS value in all areas in the MLC group, followed by that in the DLPC group. The precision evaluation revealed the lowest RMS value in all areas in the MLC group. Statistically significant differences were observed among the groups in the external, intaglio, and marginal surface (P < 0.05). ConclusionsAlthough the restorations fabricated using SM revealed higher accuracy, the crowns manufactured using SLA and DLP methods were considered clinically acceptable. Clinical SignificanceIn the production of zirconia crowns, subtractive manufacturing continues to demonstrate significantly higher accuracy compared to additive manufacturing. However, crowns fabricated using the additive manufacturing method also demonstrated high accuracy.

Exosome-like genistein-loaded nanoparticles developed by thin-film hydration and 3D-printed Tesla microfluidic chip: A comparative study

Exosomes are naturally derived information carriers that present interest as drug delivery systems. However, their vague cargo and isolation difficulties hinder their use in clinical practice. To overcome these limitations, we developed exosome-like nanoparticles, consisted of the main lipids of exosomes, using two distinct methods: thin-film hydration and 3D-printed microfluidics. Our novel microfluidic device, fabricated through digital light processing printing, demonstrated a favorable architecture to produce exosome-like nanoparticles. We compared these two techniques by analyzing the physicochemical characteristics (size, size distribution, and ζ-potential) of both unloaded and genistein-loaded exosome-like nanoparticles, using dynamic and electrophoretic light scattering. Our findings revealed that the presence of small lipophilic molecules, cholesterol and/or genistein, influenced the characteristics of the final formulations differently based on the development approach. Regardless of the initial differences of the formulations, all exosome-like nanoparticles, whether loaded with genistein or not, exhibited remarkable colloidal stability over time. Furthermore, an encapsulation efficiency of over 87% for genistein was achieved in all cases. Additionally, thermal analysis uncovered the presence of metastable phases within the membranes, which could impact the drug delivery efficiency. In summary, this study provides a comprehensive comparison between conventional and innovative methods for producing complex liposomal nanosystems, exemplified by exosome-like nanoparticles.

Evaluation of the influence of different build angles on the surface characteristics, accuracy, and dimensional stability of the complete denture base printed by digital light processing

PurposeThis study aims to investigate the influence of the build angle on the surface characteristics, accuracy, and dimensional stability of digital light processing (DLP) printed resin bases. Material and methodsRectangular and complete denture base samples were fabricated at 0, 45, and 90-degree angles (n = 5 for rectangular samples; n = 10 for maxillary and mandibular denture base samples) using a DLP printer. Surface morphology and roughness were assessed using a profilometer, followed by measuring hydrophilicity with a contact angle meter. Accuracy (trueness and precision) and dimensional stability were evaluated at intervals of 1, 3, 7, 14, 28, and 42 days after base printing using best-fit-alignment and deviation analysis in 3D software. Statistical analysis was performed using one-way ANOVA for surface characteristics (α = 0.05), multi-way ANOVA for accuracy and dimensional stability data, and Tukey's test for post-hoc comparisons. ResultsThe 0-degree group exhibited significantly lower mean roughness (1.27 ± 0.19 μm) and contact angle (80.50 ± 3.71°) (P < 0.001) compared to the 90-degree and 45-degree groups. The 0-degree build angle led to superior trueness (maxilla: 77.80 ± 9.35 μm, mandible: 61.67 ± 10.32 μm) and precision (maxilla: 27.51 ± 7.43 μm, mandible: 53.50 ± 15.16 μm) compared to other groups (P < 0.001). Maxillary base precision was superior to mandibular base precision (P < 0.001). The maxillary base exhibited less dimensional deviation than the mandibular base. The 90-degree group showed the highest deviation compared to the other two groups, and all groups' deviations increased over time (P < 0.001). ConclusionsThe build angle significantly influences the surface characteristics, accuracy, and dimensional stability of DLP-printed denture bases. A 0-degree build angle provides the most favorable performance. The maxillary base displayed superior precision and dimensional stability than the mandibular base.

Metal-Plastic Hybrid Additive Manufacturing to Realize Small-Scale Self-Propelled Catalytic Engines.

Microengines driven by catalytic decomposition of a fuel have been an interesting research area recently due to their diverse applications, such as environmental monitoring and drug delivery. Literature reports a number of studies on this topic where researchers have made various attempts to manufacture such microengines. Some such methods are deposition of catalytic metal layers on sacrificial photoresists, electrochemical deposition of metal layers on polymeric structures, or 3D printing of structures followed by multi-step loading of structures with catalysts. These methods, even though proven to be effective, are tedious, time-consuming, and expensive. To address these issues, herein we report a 3D printing technique to realize microengines in a simple, rapid, and inexpensive single-step process. The printing of various shapes of microengines is achieved using digital light processing printing of a catalyst resin, where Pd(II) acts as a catalyst resin. The proposed integrated molding process can achieve cost-effective preparation of high-efficiency microengines. We demonstrate the locomotion of these microengines in 30% (w/w) H2O2 through the decomposition of H2O2 to generate oxygen to facilitate the self-propelled locomotion. The study characterizes the microengine based on several factors, such as the role of H2O2, Pd, shape, and design of the microengine, to get a full picture of the self-locomotion of microengines. The study shows that the developed method is feasible to manufacture microengines in a simple, rapid, and inexpensive manner to be suitable for numerous applications such as environmental monitoring, remediation, drug delivery, diagnosis, etc., through the modification of the catalyst resin and fuel, as desired.

Effects of light exposure intensity and time on printing quality and compressive strength of β-TCP scaffolds fabricated with digital light processing

Digital light processing (DLP), derived from stereolithography (SL), is a lithography-based additive manufacturing (AM) process that offers the ability to tailor scaffold shape, size, material, and biometrics of fabricated scaffolds to patient requirements. The additive manufacturing of tricalcium phosphate (TCP) bioceramic scaffolds via DLP is explored in the proceeding research paper. Particularly, the role of exposure intensity and exposure time on resultant scaffold quality and mechanical properties is studied. Increased exposure intensity results in an increased deviation from the designed lattice structure and thus an increase in compressive strength. Scaffolds produced with the highest exposure intensity, resulted in a 27.6 % error increase in mean beam diameter, resulting from an increased scattering effect, penetration depth, and over-curing of peripheral slurry. TCP scaffolds with an exposure time of 3.5 s and exposure intensity of 40 mW/cm2 possessed the highest print accuracy, resulting in the lowest average compressive strength – 82 MPa for the scaffolds of cube structure and 48 MPa for the ones of I-WP structure. Statement of significanceDigital light processing (DLP) is an effective additive manufacturing (AM) method applicable for bioceramics. This study focuses on the influence of light exposure intensity on scaffold quality and compressive strength. The increase of exposure intensity can improve the compressive strength with the sacrifice of structure accuracy. The conclusions of this study can provide insights into the relationship of DLP printing parameters and scaffolds quality.

Digital light processing of customized elastic scaffolds by efficient thiol-yne crosslinking

Digital light processing (DLP) based 3D printing technology has the advantages of fast printing rate and high spatial resolution in the manufacture of tissue engineering scaffolds. However, the limited availability of printable materials for DLP technology, especially the lack of biodegradable elastomeric materials hinders the development of customized soft tissue scaffolds. Herein, liquid poly(4-methyl-ε-caprolactone) dialkynylate (PMCLDY) was prepared as a DLP printable ink based on efficient thiol-yne photocrosslinking. With the aid of photorheology and in situ FT-IR and tensile tests, an ink formulation for DLP printing was optimized as the P50 ink (PMCLDY to diluent PEGDY mass ratio of 1), which possessed fast cure rates (<15 s), low viscosity (<2 Pa·s), moderate mechanical properties (failure strain > 40 %) and maximum toughness (0.153 MJ·m−3). A commercial DLP printer equipped with the P50 ink realized 3D scaffolds models with microstructure and macroscopic shape precisely. It was demonstrated that the 3D printed scaffold with biodegradability could withstand dynamic compression cycles. Furthermore, the cytocompatibility experiments showed that the scaffold could effectively support the growth and proliferation of rat bone marrow stromal cells (BMSCs). These results demonstrate that the P50 ink is a promising material for manufacturing elastic scaffolds by DLP printing for tissue engineering applications.