Photopolymerization 3D Printing Research Articles

Bioderived Dyes-Mediated Vat Photopolymerization 3d Printing of Chitosan Hydrogels for Tissue Engineering

Bioderived Dyes-Mediated Vat Photopolymerization 3d Printing of Chitosan Hydrogels for Tissue Engineering

Fabrication of ceramics using photosensitive slurries: A comparison between UV-casting replication and vat photopolymerization 3D printing

The development of photosensitive ceramic slurries for vat photopolymerization (stereolithography or digital light processing) has received much effort in recent years. However, many of these ceramic suspensions have high viscosity and they are suitable for use only on equipment, specialized in ceramic additive manufacturing. In this work, ceramic manufacturing using photocurable slurries was tested in a low-cost vat photopolymerization printer and in silicone moulds for UV-casting replication, with the latter approach still scarcely explored in the literature. Both processes were able to produce ceramic parts. The UV-casting replication was able to work with more viscous photocurable ceramic slurries and proved more suitable for the manufacturing of ceramic parts with larger cross-sections, providing pieces with improved flexural strength to those produced by additive manufacturing. This work presents the possibility of UV-casting photosensitive slurries to manufacture ceramics, an approach that could be easily adopted without high equipment costs.

Effect of Different Sintering Additives Type on Vat Photopolymerization 3d Printing of Al2o3 Ceramics

Effect of Different Sintering Additives Type on Vat Photopolymerization 3d Printing of Al2o3 Ceramics

3D printed, environment tolerant all-solid-state capacitive ionic skin

By the photopolymerization 3D printing of photopolymerizable deep eutectic solvents, a stable and sensitive solid-state capacitive ionic skin is reported.

3D-printed microneedles with open groove channels for liquid extraction.

Microneedles (MNs) offer a simple and minimally invasive way to sample skin interstitial fluid for bioanalysis. Through the integration with portable or wearable sensing devices, it allows us to get qualitative information about some biomarkers in situ. This work is to show a MN platform with open groove channels that are manufactured using photopolymerization 3D printing. The grooves on the needle surface permit that liquid flows from the tips to the base under the influence of capillary force. The ultimate MN device can penetrate skin and tissues and sample liquid in the skin model. By taking the glucose as the model biomarker, we demonstrate that the biomarkers in the extracted liquid can be analyzed in situ by the commercial test strips attached to the back.

Complex SiC-based structures with high specific strength fabricated by vat photopolymerization and one-step pyrolysis

Lightweight and strong silicon carbide (SiC) ceramics with complex lattice structures were fabricated by vat photopolymerization 3D printing technology followed by a one-step pyrolysis process. The UV-light penetration depth of the SiC ceramic slurries was increased more than three times based on the formation of [email protected]2 [email protected] structured particles through pre-oxidation processing. To reduce the sintering temperature and shrinkage of SiC ceramics, 40 vol% solid loading [email protected]2 ceramic slurries mixed with photocurable resins containing 0–70 wt% of polysiloxane were prepared. [email protected]2/SiOC ceramic with less than 8% linear shrinkage rate was obtained after pyrolysis at 1000–1200 ℃. The pyrolyzed [email protected]2/SiOC lattice ceramics exhibited a specific strength of 4.6 × 104 N m/kg with a cellular density of 0.87 g/cm3, surpassing various other lattice structures and porous ceramics with similar porosity. The complex structure forming ability, mechanical performance and its short developing cycle make this technology to be a promising method for structural integrated SiC ceramic manufacturing.

Validation of CL‐20‐based Propellant Formulations for Photopolymerization 3D Printing

AbstractThe combustion performances of propellants depend on the geometry and the composition. Three‐dimensional (3D) printing or additive manufacturing provides a feasible and effective way to fabricate propellants according to interior ballistic requirements. The main objective of this paper is to improve the properties of 3D printed propellants in terms of energy content and combustion behavior. Three propellant formulas, which contain polyurethane‐acrylic acid resin as binder and hexanitrohexaazaisowurtzitane (CL‐20) as energetic filler, were fabricated by extrusion material 3D printing. The formulas with the force constant of 1107.43–1209.44 J/g were designed. The combustion behaviors of designed formulas, such as the maximum pressure, burn time, and burn rate, were characterized by closed bomb tests. Meanwhile, the curing time, printability, and inner structure of these formulas were also demonstrated to understand the 3D extrusion printing of propellants better.

A focused simulation-based optimization of print time and material usage with respect to orientation, layer height and support settings for multi-pathological anatomical models in inverted vat photopolymerization 3D printing

Background3D printing of anatomical models requires multi-factorial decision making for optimal model manufacturing. Due to the complex nature of the printing process, there are frequently multiple potentialities based on the desired end goal. The task of identifying the most optimal combination of print control variables is inherently subjective and rests on sound operator intuition. This study investigates the effect of orientation, layer and support settings on print time and material usage. This study also presents a quantitative optimization framework to jointly optimize print time and material usage as a function of those settings for multi-pathological anatomical models.MethodsSeven anatomical models representing different anatomical regions (cardiovascular, abdominal, neurological and maxillofacial) were selected for this study. A reference cube was also included in the simulations. Using PreForm print preparation software the print time and material usage was simulated for each model across 4 orientations, 2 layer heights, 2 support densities and 2 support tip sizes. A 90–10 weighted optimization was performed to identify the 5 most optimal treatment combinations that resulted in the lowest print time (90% weight) and material usage (10% weight) for each model.ResultsThe 0.1 mm layer height was uniformly the most optimal setting across all models. Layer height had the largest effect on print time. Orientation had a complex effect on both print time and material usage in certain models. The support density and the support tip size settings were found to have a relatively minor effect on both print time and material usage. Hollow models had a larger support volume fraction compared to solid models.ConclusionsThe quantitative optimization framework identified the 5 most optimal treatment combinations for each model using a 90–10 weighting for print time and material usage. The presented optimization framework could be adapted based on the individual circumstance of each 3D printing lab and/or to potentially incorporate additional response variables of interest.

Solvent-Free Three-Dimensional Printing of Biodegradable Elastomers Using Liquid Macrophotoinitiators

Vat photopolymerization 3D printing provides new opportunities for the fabrication of tissue scaffolds and medical devices. However, for the manufacturing of biodegradable elastomers, it usually requires the use of organic solvents to dissolve the solid photoinitators and achieve low resin viscosity, making this process environmentally unfriendly and not optimal for biomedical applications. Here, we report solvent-free 3D printing of biodegradable elastomers by digital light processing with well-defined photoinitiator–polymer conjugates. Being in liquid state at room temperature, the macrophotoinitiators enabled high-quality 3D printing in the absence of any organic solvents that are usually used in digital light 3D printing. This allowed the systematic investigation of structure–property relationships of 3D-printed biodegradable elastomers without the interference from reactive diluents. The developed macrophotoinitiators were compatible with various photopolymers and could be applied for solvent-free fabrication of biodegradable shape-memory devices. This work offers new perspectives for the solvent-free additive manufacturing of bioresorbable medical implants and other functional devices.

Vat Photopolymerization 3D Printing of Advanced Soft Sensors and Actuators: From Architecture to Function

AbstractFabrication and assembly of flexible sensors and soft actuators play important roles in improving the performance of wearable electronics and soft robots. Traditional manufacturing techniques have limitations in controlling the geometry and architecture of many soft actuation and sensing systems, which compromise their performance as well as applications. With the emergence of 3D printing, directly transforming 3D models into real objects becomes possible. In particular, vat photopolymerization techniques, represented by stereolithography, are capable of printing all‐in‐one and lab‐on‐a‐chip devices with fast speed and high accuracy. Novel polymer formulations, including functional resins, hydrogels, elastomers, polymer blends, composites, and biological materials, have been developed for vat photopolymerization 3D printing to produce highly stable architectures, which prompts a remarkable revolution in mechanics and materials for soft electronics. This review looks into the recent developments of vat photopolymerization 3D printing technology for lightweight engineering, personalized electronics, and soft robots.

3D Printing of Recyclable Elastomers with Controllable Degradation and Adhesive Properties

Photopolymerization-based 3D printing is now a well-established manufacturing technique for a wide range of applications, as it allows the customized fabrication of objects with high resolution, tunable mechanical properties, and various functionalities. However, after printing, the crosslinked polymeric networks cannot be easily degraded and recycled, raising economic and environmental concerns. To date, only a few reprocessable or partially recyclable 3D printing resins have been reported. These resins are based on complex formulations or specific chemical structures. In addition to their high production costs and their limited scope of applicability, none of these materials can be completely depolymerized after photopolymerization 3D printing. Here, a general strategy is proposed to design degradable and recyclable photopolymers for 3D printing by taking advantage of the reversible aza-Michael addition reaction. With this approach, complete degradation of printed objects can be achieved under ambient conditions with tunable kinetics. The depolymerized products can be recycled and directly used for re-printing without the need of adding extra resins. Furthermore, using dopamine as a representative monomer, the possibility of incorporating additional chemical functions into the printed materials, such as adhesive properties, is demonstrated.

Study on High-speed Continuous Photopolymerization 3D Printing Process and Properties of Printed Resin Parts

Study on High-speed Continuous Photopolymerization 3D Printing Process and Properties of Printed Resin Parts

Noncontact restoration of missing parts of stone Buddha statue based on three-dimensional virtual modeling and assembly simulation

Three-dimensional (3D) digital technology is an essential conservation method that complements the traditional restoration technique of cultural artifacts. In this study, 3D scanning, virtual restoration modeling, and 3D printing were used as a noncontact approach for restoring a damaged stone-seated Bodhisattva (stone Buddha statue). First, a 3D model with an average point density of 0.2 mm was created by integrating the fixed high-precision scanning of the exterior and the handheld mid-precision scanning of the interior excavated hole. Using a 3D deterioration map of the stone Buddha statue, the area of the missing parts was measured to be 400.1 cm2 (5.5% of the total area). Moreover, 257.1 cm2 (64.2% of the missing part area) of four parts, including the head, surrounding area of the Baekho, right ear, and right eye, for which symmetry was applicable for modeling or there could be ascertainable historical evidence for the total missing parts, was selected for restoration. The virtual restoration of the missing parts of the stone Buddha statue was performed using a haptic modeling system in the following order. First, the location of the three fragments detached from the head was determined. Next, a reference model was selected, and its symmetrization and modification with respect to the original model were conducted. Further, estimation modeling and outer shape description were achieved through historical research and consultation with experts. The heuristic-based assembly suitability of the created virtual restoration model (461 cm3) was verified by design mockup printing and digital–analog simulation. In particular, to address assembly interference, the interface surface was modified and reprocessed several times. Accordingly, the volume of the final design mockup decreased by 5.2% (437 cm3). Photopolymerization 3D printing technology was used for the actual restoration of the stone Buddha statue, and considering the surface roughness, the layer thickness of the material used for restoration was set at 0.10 mm. Finally, the surface of the printed output was colored to prevent yellowing and joined to the missing parts of the stone Buddha statue. This study presents a remarkable case of shifting from the traditional manual-contact method to the contactless digital method for restoring artifacts and is expected to largely contribute to increasing the usability of digital technologies in the restoration of cultural artifacts.

Anti-biofilm multi drug-loaded 3D printed hearing aids

Over 5% of the world's population has disabling hearing loss, which affects approximately one third of individuals over 65 years. Hearing aids are commonly used in this population group, but prolonged use of these devices may cause ear infections. We describe for the first time, the use of 3D printing to fabricate hearing aids loaded with two antibiotics, ciprofloxacin and fluocinolone acetonide. Digital light processing 3D printing was employed to manufacture hearing aids from two polymer resins, ENG hard and Flexible. The inclusion of the antibiotics did not affect the mechanical properties of the hearing aids. All multi-drug-loaded devices exhibited a hydrophilic surface, excellent blood compatibility and anti-biofilm activity against P. aeruginosa and S. aureus. Hearing aids loaded with ciprofloxacin (6% w/w) and fluocinolone acetonide (0.5% w/w) sustained drug release for more than two weeks and inhibited biofilm formation on the surface of the devices and bacteria growth in the surrounding medium. In summary, this work highlights the potential of vat photopolymerization 3D printing as a versatile manufacturing approach to fabricate high-fidelity patient-specific medical devices with anti-bacterial properties.

Optimization of Materials Composition and UV-VIS Light Wavelength Towards Curing Time Performance on Development of Tissue Engineering Scaffold

VAT photopolymerization 3D printing is a process that solidified a vat of liquid photopolymer resin solution into desired products in the presence of UV light. Achieving an optimal property with shorter curing time is an ultimate goal when using functional or special resins. In this study, the effect of wavelength with different compositions of UHT resin mixed PEG solution is studied. Different sources of light were identified, which is UV-A with a wavelength of 365 nm and VIS with a wavelength greater than 420 nm. The PEGconcentrations were varied at 40%, 50%, and 60%. While UHT concentration ratio added into solution was 30%, 50%, and 70%. It has been observed that the optimum curing under UV and VIS wavelength were 9.55 minutes and 17.48 minutes respectively. The feasible range to optimize results of curing time, PEG 48%and UHT 41% with the result 8.6 minutes for the UV-A. Meanwhile, for VISwavelength, PEG 49% and UHT 64% with the result 16 minutes. The success of this study will lead to further innovation on UV-VIS light source in 3D printing in terms of energy efficiency, safety, and cost as well as further evaluation of the performance with respect to the mechanical properties of tissue engineering scaffold.

Ultrasound-assisted vat photopolymerization 3D printing of preferentially organized carbon fiber reinforced polymer composites

In this study, we present a new vat photopolymerization 3D printing process that uses acoustic radiation forces from ultrasonic standing waves to organize carbon short fibers within a photocurable resin. A chamber was developed to generate the standing bulk acoustic wave in the resin to align the carbon fibers along the nodes of the standing wave. The resin was then selectively cured to create constructs in the shape of a dog bone specimen by exposing to UV. The effect of fiber concentration (0.5 %, 1 %, 2 %, and 4 % w/v) and direction of alignment (parallel, perpendicular) on tensile strength of the carbon fiber reinforced polymer composites was determined. The constructs with 1 % w/v showed the highest gain in tensile strength due to the fiber alignment. For two-layered constructs with 1 % fiber concentration, 0°–0° constructs (fibers aligned along the uniaxial testing direction) demonstrated significantly higher tensile strength followed by 0°–90°constructs compared to constructs with randomly distributed fibers and without fibers.

Fabrication of High Permittivity Resin Composite for Vat Photopolymerization 3D Printing: Morphology, Thermal, Dynamic Mechanical and Dielectric Properties.

The formulation of a high dielectric permittivity ceramic/polymer composite feedstock for daylight vat photopolymerization 3D printing (3DP) is demonstrated, targeting 3DP of devices for microwave and THz applications. The precursor is composed of a commercial visible light photo-reactive polymer (VIS-curable photopolymer) and dispersed titanium dioxide (TiO2, TO) ceramic nano-powder or calcium copper titanate (CCT) micro-powder. To provide consistent 3DP processing from the formulated feedstocks, the carefully chosen dispersant performed the double function of adjusting the overall viscosity of the photopolymer and provided good matrix-to-filler bonding. Depending on the ceramic powder content, the optimal viscosities for reproducible 3DP with resolution better than 100 µm were η(TO) = 1.20 ± 0.02 Pa.s and η(CCT) = 0.72 ± 0.05 Pa.s for 20% w/v TO/resin and 20% w/v CCT/resin composites at 0.1 s−1 respectively, thus showing a significant dependence of the “printability” on the dispersed particle sizes. The complex dielectric properties of the as-3D printed samples from pure commercial photopolymer and the bespoke ceramic/photopolymer mixes are investigated at 2.5 GHz, 5 GHz, and in the 12–18 GHz frequency range. The results show that the addition of 20% w/v of TO and CCT ceramic powder to the initial photopolymer increased the real part of the permittivity of the 3DP composites from ε’ = 2.7 ± 0.02 to ε’(TO) = 3.88 ± 0.02 and ε’(CCT) = 3.5 ± 0.02 respectively. The present work can be used as a guideline for high-resolution 3DP of structures possessing high-ε.

Preparation of patterned flat-sheet membranes using a modified phase inversion process and advanced casting knife construction techniques

High fluxes and low fouling are practically highly desired in all membrane processes. One generic way to realize this is by introducing surface patterns on the membrane to increase the active area and the surface roughness. A new method to prepare flat-sheet patterned membranes using a patterned knife combined with a modified phase inversion process is now presented. After casting the polymer solution, the patterned knife shapes the top surface into the desired pattern. Non-solvent is sprayed immediately after the passage of the knife to rapidly solidify the polymer and preserve the pattern. To construct the patterned knife, different materials and techniques were evaluated: (1) an aluminium knife shaped by electrical discharge micromachining, (2) a gypsum knife shaped by powder-based 3D-printing, and (3) an acrylate resin, shaped by photopolymerization 3D-printing (stereolithography). As such, replacing the conventional non-solvent contact in the phase inversion via immersion by spraying already increased membrane permeance, but a significant further increase of permeance resulted from the increased surface area realized through the patterning. A minimum viscosity of the casting solution of around 7.5–10 Pa.s was required to realize well-pronounced patterns on the membrane, as screened for polyacrylonitrile and cellulose acetate, both dissolved in dimethyl sulfoxide and using water as non-solvent.

Optimization of Curing Behavior of Si3N4 UV Resin for Photopolymerization 3D Printing

Silicon nitride (Si3N4) ceramics are widely used in mechanical and thermal management applications due to their excellent properties. To overcome the difficulties in traditional Si3N4 ceramic forming techniques, it is interesting to see the possibility of making complex-shaped silicon nitride ceramic component with novel 3D printing methods. In this study, we aim to study the effect of photo-initiators on the curing behavior of pre-formulated Si3N4 ceramic UV resin suspension. To elucidate the potential multi-factor interactions, a statistic experiment design was implemented in a sequence of screening and optimization by using Modde software. It was found that the kinds of photo-initiators, total amount of initiators and the mixture ratio between initiators have a great influence on the curing properties of silicon nitride UV ceramic resin. Based on these results, a formula was selected based on the criterion of using least amount photo-initiator while reaching the highest curing thickness.

Selective Reactivity of Myrcene for Vat Photopolymerization 3D Printing and Postfabrication Surface Modification.

Biosourced materials are gaining interest industrially, but there are still limitations on the library of available materials suitable for advanced manufacturing, especially using photopolymerization-based processing techniques. Terpenes, such as myrcene, are naturally produced materials possessing structural features, specifically alkenes, that avail themselves for such techniques. Free-radical and anionic polymerization techniques were used to explore molecular architecture, such as branching, as well as molecular weight and dispersity on physical properties prior to the production of 3D printing photopolymer resins. The polymyrcene resins were printed into dogbones and mold templates for soft materials. Model reactions with monofunctional thiols were used to demonstrate the potential for postpolymerization and fabrication functionalization, accompanying a physical demonstration where the surface hydrophobicity of polymyrcene could be tuned from superhydrophobic when using an alkyl chain monothiol (greater than 100° water contact angle) to a hydrophilic surface displaying a water contact angle of less than 45° compared with that of the unmodified surface (∼60°). Tunable bulk and surface properties are a unique feature for 3D printing materials and demonstrate the potential of polymyrcene and other biosourced photopolymers to a wide range of research applications.