DLP 3D Research Articles

World's First Tribo Material for DLP 3D Printing

World's First Tribo Material for DLP 3D Printing

High-performance and high-precision Al2O3 architectures enabled by high-solid-loading, graphene-containing slurries for top-down DLP 3D printing

To date, obtaining the high-solid-loading Al2O3 slurry and overcoming the trade-off between high solid loading and printing accuracy and strength of printed green bodies to achieve high-performance and precision Al2O3 ceramic parts by DLP 3D printing remain challenging. In this study, an Al2O3 slurry with high solid loading of 60 vol% was developed through dispersant optimisation for top-down DLP 3D printing. Graphene was innovatively introduced during slurry fabrication to decouple the printing accuracy and strength of green bodies from such high solid loading. Simultaneously, graphene addition could considerably reduce slurry fluidity, thereby facilitating its coordination with top-down DLP. With 0.07 wt% graphene addition, the dimension deviations of printed green bodies improved from 90 to 880 µm to ≤ 70 µm, and the bending strength increased by 17.75%. High-performance and precise Al2O3 ceramic components with low sintering shrinkages were prepared. The density and microhardness were 99.7% and 18.61 GPa, respectively.

3D printed dental protheses using TPO-initiated photopolymerization. Effect of the photoinitiator concentration and the use of a UV-blocker

ABSTRACT A DLP 3D printer was used to reproduce several objects (a trunk scaffold, a cube, and a dental crown) in order to ascertain the conditions to obtain the best resolution. The polymerizing solution was a mixture of BisGMA, TEGDMA, and UDMA monomers. The photoinitiator was triphenyl phosphinic oxide (TPO) at various concentrations in the presence and absence of the UV-light blocker 2.5-bis (5’-tert-butyl 2-benzoxazolyl)thiophene (Datilux OB). The printed objects were analyzed by Scanning Electron Microscopy. It was found that the best results were obtained using concentrations of 1 and 2% m/m of TPO in the presence of 0.1% of the UV-blocker. This blocker has an absorption spectrum similar to the photoinitiator and avoids secondary photoinitiations due to reflections that may cause imperfections in the printed objects. The effect of the UV-blocker was evaluated by thermal analysis of the obtained polymers showing that in the presence of the blocker 3–4 times more monomers remained unpolymerized, indicating that the more irregular objects were due to the excess of undesired polymerization. ShoreD hardness of the dental crown material was around 80, within the values reported for other dental materials.

Synthesis and UV Cross‐Linking of Methacrylated Linear and Star‐Shaped Lactide Oligomers as Potential Biodegradable Resins for Stereolithography

AbstractStereolithography and DLP printing attract a lot of attention in medical field as techniques for fabrication of personalized implants and various medical devices. However, there is a lack of photo‐curable resins for fabrication of biodegradable tissue engineering constructs and implants. In this work biodegradable UV‐curable d,l‐lactide oligomers are presented, which can be good candidates as resins for SLA and DLP 3D printing. Linear and star‐shaped (3‐ and 6‐arm) methacrylated d,l‐lactide oligomers with different molecular weight are synthesized and cross‐linked in various conditions. UV‐curing is performed at elevated temperatures in the absence of any diluents and revealed formation of gel fraction, which has achieved 99%. The cross‐linked materials demonstrate high tensile modulus (up to 1.8 GPa), suggesting the resins are perspective for fabrication of load‐bearing implants.

DLP 3D printed silica-doped HAp ceramic scaffolds inspired by the trabecular bone structure

HAp has drawn great attention in recent years for its similarity to the inorganic component of bone. However, the application is limited due to its poor shape ability, low mechanical property, and biodegradability. In this work, silica-doped HAp ceramic scaffolds are 3D printed with a natural optimized trabecular bone structure.Specifically, with the addition of silica, composite scaffolds sintered at 1200 °C exhibit a decrease of pores and increase of grain size, yielding a compressive strength increased from 3.93±0.75 MPa to 12.94±0.70 MPa, comparable to the trabecular bone. Results of XRD and SEM illustrate that the addition of silica promotes the formation of the bioactive TCP phase. Biological characterization in SBF illustrates that the in vitro bioactivity of the silica-doped scaffolds is superior to that of the pure HAp, and the scaffolds are biodegradable. Cytocompatibility study revealed that there is no potential cytotoxicity for L929 cells on all groups of scaffolds.Trabecular bone structure-mimicking silica-doped ceramic scaffolds with high strength and in vitro bioactive are developed. The Silica-doped ceramic scaffolds can be tailored to certain biological response requirements as a promising material for bone defect regeneration.

Multi‐Color 3D Printing via Single‐Vat Grayscale Digital Light Processing

AbstractDigital light processing (DLP) is a high‐resolution, high‐speed additive manufacturing method that builds 3D parts by selectively curing photopolymerizable resins layer‐by‐layer. To achieve multi‐color DLP printing, researchers have used multiple switchable resin vats. However, these methods require complex vat switching devices and cleaning manipulations, leading to low efficiency. Therefore, it remains a challenge to achieve multi‐color DLP 3D printing efficiently. In this study, a single‐vat multi‐color DLP 3D printing by using an anthraquinone‐based dye is realized. The dye can be oxidized by the free radicals released from photoinitiators under ultraviolet light and change the color from blue to yellow. This color‐changing mechanism permits a graded spectrum of colors as concomitants of the photopolymerization process during DLP printing by controlling the light dose without using extra vats or devices. Multi‐color demonstrations, such as engineering stress simulation results in 3D and multi‐color vases, are successfully fabricated, showing great versatility and efficiency.

Preparation and Stability of PEGDA/GO Conductive Materials by DLP 3D Printing

Preparation and Stability of PEGDA/GO Conductive Materials by DLP 3D Printing

수계 PUA/PEGDMA 혼합 올리고머 레진에 의한 DLP 3D 프린팅 결과물의 기계적 물성 향상 및 레진 희석액의 여과특성 분석

본 연구에서는 상용 수계 polyurethane acrylate(PUA)와 poly(ethylene glycol) dimethacrylate(PEGDMA) 기반의 수계 레진을 digital light processing(DLP) 방식으로 3D 프린팅하였다. 출력물의 기계적 물성 조사를 통해 PUA와 PEGDMA를 모두 포함하는 경우 단일 올리고머 레진에 비해 높은 기계적 물성을 나타냄을 확인하였다. 출력물은 물 세척만으로 표면 잔류 레진이 모두 제거되었고, 세척폐액의 수질오염에 대한 영향을 비교하기 위해 레진 희석액 내 부유물의 크기 분포 및 여과효과를 조사한 결과 모든 레진 조성물에서 0.45 ㎛ 공극 필터에 의해 부유물이 1/3 미만으로 감소함을 확인하였다. 물 세척이 가능하며 여과에 의해 세척액 내 부유물의 효과적인 제거가 가능한 수계 레진은 수질오염을 저감하여 DLP 3D 프린팅의 보급에 기여할 것으로 예상한다.

3D printing of complex-shaped polymer-derived ceramics with enhanced structural retention

ABSTRACT The combination of polymer-derived ceramics and DLP 3D printing has significant advantages for manufacturing special polynary ceramics with complex structures. However, a large number of the organic components in the precursor rapidly burn out and release after evaporation during pyrolysis. This leads to structural retention issues such as sample deformation, shrinkage and cracking. The surface morphology and accuracy of the sample are greatly affected by the escape of organic matter and the release of thermal stress during the pyrolysis process. Therefore, this study employs the method of adding low-melting-point silicone oil based on the original material components. The slow burn-out process of silicone oil at a lower temperature can produce fine pores, which would aid the release of thermal stress. Additionally, it can provide channels for escape of the organic gas at high-temperature, which helps to reduce large deformation and cracking and improves the surface morphology and dimensional accuracy of the final pyrolyzed samples. The method studied in this work helps to enhance the structural retention of complex-shaped polymer-derived ceramics manufactured by 3D printing and high-temperature pyrolysis, which could be beneficial to the further mass fabrication of such ceramic products.

DLP printing of a flexible micropattern Si/PEDOT:PSS/PEG electrode for lithium-ion batteries.

We report on a free-standing 3D-printed Si/PEDOT:PSS/PEG electrode based on silicon nanoparticles (Si) as an active material for lithium-ion batteries (LIBs) that are fabricated by 3D printing via digital light processing (DLP). Compared with the Si electrode prepared by the traditional method, the 3D-printed Si/PEDOT:PSS/PEG electrode developed by DLP preserves a specific discharge capacity of 1658.4 mA h g-1, with a capacity fade of 0.3% per cycle at a current density of 800 mA g-1 after 125 cycles. This helps in maintaining its structural integrity and enables it to exhibit significantly high flexibility with an enhanced load of 4.2 mg cm-2. The resulting free-standing electrode shows that 3D printing has significant potential for application to a variety of LIB technologies.

A high-performance GelMA–GelMA homogeneous double-network hydrogel assisted by 3D printing

Gelatin methacryloyl (GelMA) is a popular photocrosslinkable hydrogel that has been widely utilized in tissue engineering and regenerative medicine fields due to its excellent biocompatibility, biodegradability and cell response. However, the lack of mechanical properties limits its application. In the present study, a method for the preparation of a GelMA-GelMA (G-G) homogeneous double-network (DN) hydrogel to improve mechanical strength based on DLP 3D printing is proposed. The G-G DN hydrogel was fabricated and characterized in terms of microstructure, mechanical properties and rheological behavior. By modifying the degree of substitution (DS), the polymer concentration of double network crosslinking and the soak time, the novel G-G DN hydrogel could significantly improve the properties of strength, self-recovery and fatigue resistance. After all, the novel porous composite hydrogel (G-G DN hydrogel) could achieve more than twice that of the pure GelMA hydrogel, better fatigue resistance and printable ability. Therefore, it can be a potential choice of applications attracting great attention for its mechanical properties, great transmittance and biocompatibility.

Property Analysis of Photo-Polymerization-Type 3D-Printed Structures Based on Multi-Composite Materials

Additive manufacturing, commonly called 3D printing, has been studied extensively because it can be used to fabricate complex structures; however, polymer-based 3D printing has limitations in terms of implementing certain functionalities, so it is limited in the production of conceptual prototypes. As such, polymer-based composites and multi-material 3D printing are being studied as alternatives. In this study, a DLP 3D printer capable of printing multiple composite materials was fabricated using a movable separator and structures with various properties were fabricated by selectively printing two composite materials. After the specimen was fabricated based on the ASTM, the basic mechanical properties of the structure were compared through a 3-point bending test and a ball rebound test. Through this, it was shown that structures with various mechanical properties can be fabricated using the proposed movable-separator-based DLP process. In addition, it was shown that this process can be used to fabricate anisotropic structures, whose properties vary depending on the direction of the force applied to the structure. By fabricating multi-joint grippers with varying levels of flexibility, it was shown that the proposed process can be applied in the fabrication of soft robots as well.

Development of software and hardware components to the Internet of an additive manufacturing system based on vat photopolymerization technology

The global competition and shifts in consumer’s demand are forcing companies to enhance their productivity by reducing the manufacturing time, cost and increasing the value of final merchandise. Recent engineering researchers find that the additive manufacturing (AM) process could be an innovative solution due to its advantages in building complex shapes using different materials. However, the lack of developing tools to automate AM equipment has limited applying this technique to fabricate products within a production system. Thus, an internet of additive manufacturing(IoAM) system for the Vat photopolymerization process is proposed. The IoAM system is composed of three components which are described. The first one is the machine hardware integrated by all the various mechanical parts of a conventional Bottom-Up DLP 3D printer managed by a control board based on IoT technology. The second element is a web interface that controls and monitors a single or an array of machines from one or multiple operators and devices. The last module is firmware, which is the intermediary between the software and hardware. Besides, it is responsible for executing the adaptive control for the printing parameters, which has allowed to speed up the manufacturing process. The geometric calibration method to overcome distortion of photomask produced by DLP and the energy calibration algorithm to solve the non-uniform energy distribution have permitted to fabricate objects with high resolution around 30um in the XY axis and 50 μm as a layer thickness.

Preparation of Photocurable Slurry for DLP 3D Printing Process using Synthesized Yttrium Oxyfluoride Powder

Preparation of Photocurable Slurry for DLP 3D Printing Process using Synthesized Yttrium Oxyfluoride Powder

Preparation of a High-Precision Gama-Al2O3 Structured Catalyst by DLP 3D Direct Printing for Hydrogen Production from Methanol

Preparation of a High-Precision Gama-Al₂O₃ Structured Catalyst by DLP 3D Direct Printing for Hydrogen Production from Methanol

Comparison of Intaglio Surface Trueness of Interim Dental Crowns Fabricated with SLA 3D Printing, DLP 3D Printing, and Milling Technologies.

This study aimed to evaluate the intaglio surface trueness of interim dental crowns fabricated with three 3-dimensional (3D) printing and milling technologies. Dental crown was designated and assigned as a computer-aided design (CAD) reference model (CRM). Interim dental crowns were fabricated based on CRM using two types of 3D printer technologies (stereolithography apparatus and digital light processing) and one type of milling machine (n = 15 per technology). The fabricated interim dental crowns were obtained via 3D modeling of the intaglio surface using a laboratory scanner and designated as CAD test models (CTMs). The alignment and 3D comparison of CRM and CTM were performed based on the intaglio surface using a 3D inspection software program (Geomagic Control X). Statistical analysis was validated using one-way analysis of variance and Tukey HSD test (α = 0.05). There were significant differences in intaglio surface trueness between the three different fabrication technologies, and high trueness values were observed in the milling group (p < 0.05). In the milling group, there was a significant difference in trueness according to the location of the intaglio surface (p < 0.001). In the manufacturing process of interim dental crowns, 3D printing technologies showed superior and uniform manufacturing accuracy than milling technology.

The Trueness of Obturator Prosthesis Base Manufactured by Conventional and 3D Printing Techniques.

To compare the intaglio surface trueness of obturator prosthesis bases manufactured by traditional compression molding, injection molding, and 3D printing techniques. A complete edentulous master cast with Aramany Class I maxillary defect was selected for this in vitro study. Four study groups (n = 10/group) were included in this study, Group A: Compression Molding, Group B: Injection Molding, and Group C: Cara Print 3D DLP Printer, and Group D: Carbon 3D DLS Printer. All obturator prostheses' intaglio surfaces were scanned with a laboratory scanner (E4; 3Shape Inc, New Providence, NJ) and the dimensional differences between study samples and their corresponding casts were calculated as the root mean square (measured in mm, absolute value) using a surface matching software (Geomagic design X; 3D Systems, Rock Hill, SC). One-way Analysis of variance (ANOVA) and Fisher's least significant difference (LSD) test were used to compare groups differences in RMS (α = 0.05). There was a significant effect of manufacturing technique on the RMS values for the 4 conditions [F(3,36) = 5.743, p = 0.003]. Injection Molding (0.070 mm) and Compression Molding groups (0.076 mm) had a lower interquartile range, and the Cara Print 3D-Printer group (0.427 mm) and Carbon 3D-Printer (0.149 mm) groups had a higher interquartile range. The Injection Molding group showed the best and uniform surface matching with the most area in green in the color maps. The Injection Molding group (0.139 ± 0.049 mm) had significantly lower RMS than all other groups (p < 0.001 for all comparisons). Compression Molding (0.269 ± 0.057 mm), Cara Print 3D-Printer (0.409 ± 0.270 mm), and Carbon 3D-Printer (0.291 ± 0.082 mm) groups were not significantly different from each other (Compression Molding versus Carbon 3D-Printer, p = 0.59; Compression Molding versus Cara Print 3D-Printer, p = 0.25; Cara Print 3D-Printer versus Carbon 3D-Printer, p = 0.40). Obturator prosthesis bases manufactured with injection molding technique showed better intaglio surface trueness than ones made by the compression molding technique and 3D printers. Although obturator prosthesis bases manufactured from different 3D printers showed similar trueness, a DLP 3D printer produced less consistent outcome than a DLS 3D printer.

Fabrication of hollow lattice alumina ceramic with good mechanical properties by Digital Light Processing 3D printing technology

In this study, two configurations of alumina (Al2O3) ceramics (hollow lattice structure and solid lattice structure) were prepared by DLP 3D printing technology. When sintered at 1600 °C for 4 h, dense alumina ceramics with an average grain size of 4.38 ± 1.26 μm can be obtained. The Al2O3 ceramics prepared by DLP process have good forming precision and shape. The dimension error can be controlled about 0.2 mm. The compressive strength of solid block is 572 MPa. The maximum compressive strength of solid lattice (2.0 mm in diameter and 45% in porosity) is 9.70 MPa. The maximum compressive strength of hollow lattice (2.0 mm in diameter, 0.3 mm in thickness and 70% in porosity) is 4.30 MPa. The thermal simulation results show that the temperature of the hollow lattice (diameter 1.2 mm, porosity 76%) with 500 °C upper surface transferring to the lower surface is only 88.6 °C, which is lower than 133 °C of the solid lattice. Hollow lattice structure can effectively reduce heat loss and improve energy efficiency. The hollow lattice structure Al2O3 ceramics formed by DLP technology is expected to be used in industrial thermal insulation applications.

Evaluation of Mechanical and Physical Properties of Light and Heat Polymerized UDMA for DLP 3D Printer.

The aims of this study were to investigate the feasibility of using a DLP 3D printer to fabricate a crown using scan data before tooth preparation, and to investigate the effect of additional heat curing on the mechanical properties of the urethane dimethacrylate (UDMA)-based 3D printed crown. A silicone fitting test was used to evaluate the internal adaptation of the crown. For ultimate tensile strength (UTS), the specimens were tested after 24 h storage in water at 37 °C or after 10,000 thermal cycles (TC) between 5–55 °C. For shear bond strength (SBS), a PMMA self-curing resin was filled into a Teflon ring mounted onto the polished UDMA specimens. The internal adaptation of the crowns fabricated with cement space was better than those with no cement space. There was no significant difference in UTS between light-curing and additional heat-curing groups after TC. As for the SBS, there was a significant difference after TC between the two groups. Crowns can be fabricated by a DLP 3D printer using pre-preparation scans with a cement space defined in the software. Additional heat curing of the UDMA-based crown reduced residual monomer and improved its mechanical properties.

Thiol‐terminated hyperbranched polymer for DLP 3D printing: Performance evaluation of a low shrinkage photosensitive resin

AbstractIn order to lower the volume shrinkage of the DLP 3D printing photosensitive resins during printing, a thiol‐terminated hyperbranched polymer (T‐HBP) was synthesized and introduced into the bisphenol A epoxy acrylate (EA) based photosensitive resin system. The obtained T‐HBP was characterized by FTIR and 1H NMR spectra, and the grafting rate of sulfhydryl was determined. The mechanical properties of the photosensitive resins were measured by tensile and impact strength measurement. The glass transition temperature of the photosensitive resins was analyzed by DSC and the impact fracture surface was observed by SEM. T‐HBP exhibited a much lower viscosity than its linear counterparts, and the addition of thiol improved the curing speed of the photosensitive resins. When the amount of T‐HBP added was 20 wt%, the shrinkage of the photosensitive resins was reduced by about 45.5% and the impact strength increased by 33.9% compared with the control. The macromolecular spherical structure of T‐HBP effectively reduced the functional group density of the photosensitive resins. In addition, the thiol‐acrylate photopolymerization introduced by T‐HBP further reduced the volume shrinkage of the photosensitive resins.