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CAD design of the DLP 3D printing test samples: (A) rectangular test samples: Shore A hardness test sample (40 x 40 x 7 mm, pink) and two flat rectangular samples (54 x 10 x 2 mm, brown and blue) with a spacing of 3 mm. (B) frontal sinus implant prototype (length ~15 mm, green) with support structures (various coloured)
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Digital Light Processing (DLP) enables high precision 3D-printing of photopolymers and holds promising potential for patient-specific implant solutions. On the material side, Poly(ethylene glycol) diacrylate (PEGDA) has emerged as an interesting material for use in biomedical applications. For adequate photopolymerization, a photoinitiator and a li...
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Context 1
... simple rectangular test samples, such as one Shore A hardness test sample (40 x 40 x 7 mm) and two flat test samples (54 x 10 x 2 mm), were printed. They were placed next to each other with a spacing of 3 mm (Figure 1 A) on the building platform. Second, a much more complex test sample of a frontal sinus implant prototype was built. ...
Context 2
... prototype is customised based on a patient's anatomical individualities. Consequently, it is a tubular structure with complex free-formed geometry that needs a support structure in order to be 3D printed ( Figure 1 B). PEGDA solutions were processed using a light exposure time per layer of 20 s and a layer height of 100 μm (Zresolution). ...
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Additive Manufacturing (AM) is a notable procedure for direct production of miniaturized polymer components, mainly due to the ability of the process to produce complex geometries with time and cost effective iteration cycles in the development of new plastic products. This study evaluate the capability of Continuous Liquid Interface Production (CL...
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... To reduce overpolymerization, we included Orange G, a water-soluble photoabsorber, used by several other groups in 3D printing of materials to enhance spatial control by absorbing UV light that is out of the focus region. 54 Notably, our hydrogels are significantly softer than those traditionally printed in most applications, with PEGDA concentrations exceeding 30% (w/w). We created solutions consisting of 0.01%, 0.02%, and 0.05% Orange G and polymerized them with different exposure times. ...
Recreating tissue environments with precise control over mechanical, biochemical, and cellular organization is essential for next-generation tissue models for drug discovery, development studies, and the replication of disease environments. However, controlling these properties at cell-scale lengths remains challenging. Here, we report the development of printing approaches that leverage polyethylene glycol diacrylate (PEGDA) hydrogels containing photocaged oligonucleotides to spatially program material characteristics with non-destructive, non-ultraviolet light. We further integrate this system with a perfusion chamber to allow us to alter the composition of PEGDA hydrogels while retaining common light-activatable photocaged DNAs. We demonstrate that the hydrogels can capture DNA functionalized materials, including cells coated with complementary oligonucleotides with spatial control using biocompatible wavelengths. Overall, these materials open pathways to orthogonal capture of any DNA functionalized materials while not changing the sequences of the DNA.
... In several previously reported cases [14][15][16][17], a UV absorber was added to make the resin photocurable. Mau et al. used photopolymer hydrogels with UV absorber orange G to increase the DLP printing performance and accuracy [18]. In other cases, silica fiber preforms were successfully fabricated using silica-loaded resin without adding any UV absorber. ...
3D printing technologies have distinguished advantages in manufacturing arbitrary shapes and complex structures that have attracted us to use digital light processing (DLP) technology for specialty silica optical fiber preforms. One of the main tasks is to develop an appropriate recipe for DLP resin that is UV sensitive and loaded with silica nanoparticles. In this work, the effects of a UV absorber in highly silica-loaded resin on DLP printing are experimentally investigated. Spot tests and DLP printing are carried out on resins with varying dosages of a typical UV absorber, Sudan Orange G. Based on the experimental results, the UV absorber can significantly improve the resolution of DLP printed green bodies while requiring a larger exposure dose.
... The gel designed for bolus application is illustrated in Figure 1A. The DLP-based 3D bioprinting technique employs a blue light (405 nm) to activate the photoinitiator LAP, leading to the generation of free radicals that initiate the breaking of C=C double bonds in AM and PEGDA [25,26] . This process results in the formation of a crosslinking network and solidification of the bioink into a desired pattern. ...
Boluses are a type of materials used to enhance skin dose during the treatment of superficial lesions. However, the current commercially available boluses cannot fully conform to irregular skin surfaces due to their uniform thickness, thereby compromising the efficacy of radiotherapy. Three-dimensional (3D) bioprinting boasts a huge potential in the creation of customized boluses, but the use of this technique is limited by shortcomings of the prevailing materials, such as their indirect printability and substance rigidity. As a potential substitute, hydrogels possessing a tensile modulus comparable to that of skin tissue are optimal candidates for customizing boluses. In this study, we developed a photocurable bioink for multifunctional boluses using digital light processing (DLP). Alginate, acrylamide, polyethylene glycol diacrylate, lithium phenyl-2,4,6-trimethylbenzoylphosphinate, and protocatechuic acid were synergistically combined to fabricate the bioink. The bolus printed using this bioink was endowed with enhanced toughness, superior adhesion, tissue equivalence, anti-dehydration and anti-bacterial properties, as well as excellent biocompatibility and radiation performance. In conclusion, the DLP-based 3D bioprinting of the proposed bioink can provide an avenue for obtaining personalized boluses in radiotherapy treatment of superficial tumors.
... In another previous study, we printed PEGDA with different amounts of water via DLP. 38 It was possible to print complex and even hollow geometries, such as a prototype of a frontal sinus implant and a frontal neo-ostium implant, respectively. However, these materials lacked flexibility with low water contents and low printing accuracy with high water contents. ...
Hydrogels are three-dimensional hydrophilic polymeric networks absorbing up to and even more than 90 wt% of water. These superabsorbent polymers retain their shape during the swelling process while enlarging their volume and mass. In addition to their swelling behavior, hydrogels can possess other interesting properties, such as biocompatibility, good rheological behavior, or even antimicrobial activity. This versatility qualifies hydrogels for many medical applications, especially drug delivery systems. As recently shown, polyelectrolyte-based hydrogels offer beneficial properties for long-term and stimulus-responsive applications. However, the fabrication of complex structures and shapes can be difficult to achieve with common polymerization methods. This obstacle can be overcome by the use of additive manufacturing. 3D printing technology is gaining more and more attention as a method of producing materials for biomedical applications and medical devices. Photopolymerizing 3D printing methods offer superior resolution and high control of the photopolymerization process, allowing the fabrication of complex and customizable designs while being less wasteful. In this work, novel synthetic hydrogels, consisting of [2-(acryloyloxy) ethyl]trimethylammonium chloride (AETMA) as an electrolyte monomer and poly(ethylene glycol)-diacrylate (PEGDA) as a crosslinker, 3D printed via Digital Light Processing (DLP) using a layer height of 100 μm, are reported. The hydrogels obtained showed a high swelling degree q∞m,t ∼ 12 (24 h in PBS; pH 7; 37 °C) and adjustable mechanical properties with high stretchability (εmax ∼ 300%). Additionally, we embedded the model drug acetylsalicylic acid (ASA) and investigated its stimulus-responsive drug release behaviour in different release media. The stimulus responsiveness of the hydrogels is mirrored in their release behavior and could be exploited in triggered as well as sequential release studies, demonstrating a clear ion exchange behavior. The received 3D-printed drug depots could also be printed in complex hollow geometry, exemplarily demonstrated via an individualized frontal neo-ostium implant prototype. Consequently, a drug-releasing, flexible, and swellable material was obtained, combining the best of both worlds: the properties of hydrogels and the ability to print complex shapes.
... SLA is a highly advanced technique for 3D printing hydrogels, using a layer-by-layer approach and UV to control photo-cross-linking [100,131]. The utilization of DLP in PEGDA hydrogel compositions, with different water content and concentrations of a photoinitiator and light absorber, demonstrated encouraging prospects for custom implant solutions tailored to individual patients [132]. Another study investigated DLP 3D printing of PEGDA-based photopolymers with dexamethasone (DEX) drug-loading, finding that drug release is prone to burst-release and DEX degrades significantly in the 3D-printed samples over time [133]. ...
In this brief review, we discuss the recent advancements in using poly(ethylene glycol) diacrylate (PEGDA) hydrogels for tissue engineering applications. PEGDA hydrogels are highly attractive in biomedical and biotechnology fields due to their soft and hydrated properties that can replicate living tissues. These hydrogels can be manipulated using light, heat, and cross-linkers to achieve desirable functionalities. Unlike previous reviews that focused solely on material design and fabrication of bioactive hydrogels and their cell viability and interactions with the extracellular matrix (ECM), we compare the traditional bulk photo-crosslinking method with the latest three-dimensional (3D) printing of PEGDA hydrogels. We present detailed evidence combining the physical, chemical, bulk, and localized mechanical characteristics, including their composition, fabrication methods, experimental conditions, and reported mechanical properties of bulk and 3D printed PEGDA hydrogels. Furthermore, we highlight the current state of biomedical applications of 3D PEGDA hydrogels in tissue engineering and organ-on-chip devices over the last 20 years. Finally, we delve into the current obstacles and future possibilities in the field of engineering 3D layer-by-layer (LbL) PEGDA hydrogels for tissue engineering and organ-on-chip devices.
... 42 Moreover, LAP is highly water soluble with high molar absorptivity ( ≈ 200 M -1 cm -1 ) and has been successfully used in DLP and SLA based printing. 43,44 Alternative photoinitiators like Irgacure-2959, Eosin Y, and 2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) were found to be inadequate due to factors such as low solubility in water, insufficient absorption at a wavelength of 365 nm (absorbance range from 400 to 800 nm), and cytotoxicity, respectively (see Supporting Information Section 10). 40,42 Since UV light attenuates and decreases in intensity when it propagates through a photoabsorber containing solution, the control over photoabsorber concentration to limit the penetration of UV light into the prepolymer solution enables control over the thickness of the cross-linked layer. ...
Three-dimensional (3D) printed hydrogels fabricated using light processing techniques are poised to replace conventional processing methods used in tissue engineering and organ-on-chip devices. An intrinsic potential problem remains related to structural heterogeneity translated in the degree of cross-linking of the printed layers. Poly(ethylene glycol) diacrylate (PEGDA) hydrogels were used to fabricate both 3D printed multilayer and control monolithic samples, which were then analyzed using atomic force microscopy (AFM) to assess their nanomechanical properties. The fabrication of the hydrogel samples involved layer-by-layer (LbL) projection lithography and bulk cross-linking processes. We evaluated the nanomechanical properties of both hydrogel types in a hydrated environment using the elastic modulus (E) as a measure to gain insight into their mechanical properties. We observed that E increases by 4-fold from 2.8 to 11.9 kPa transitioning from bottom to the top of a single printed layer in a multilayer sample. Such variations could not be seen in control monolithic samples. The variation within the printed layers is ascribed to heterogeneities caused by the photo-cross-linking process. This behavior was rationalized by spatial variation of the polymer cross-link density related to variations of light absorption within the layers attributed to spatial decay of light intensity during the photo-cross-linking process. More importantly, we observed a significant 44% increase in E, from 9.1 to 13.1 kPa, as the indentation advanced from the bottom to the top of the multilayer sample. This finding implies that mechanical heterogeneity is present throughout the entire structure, rather than being limited to each layer individually. These findings are critical for design, fabrication and application engineers intending to use 3D printed multilayer PEGDA hydrogels for in-vitro tissue engineering and organ-on-chip devices.
... Engineered hydrogel bioscaffolds have been extensively used in the area of biomedical engineering including drug delivery and tissue engineering due to their biocompatibility and the ability to tune their mechanical properties. [1][2][3][4] Additive manufacturing, such as 3D printing, of bioscaffolds offers the ability to customise morphological and mechanical properties to suit for specific tissue engineering applications such as cell encapsulations and 3D tissue formation. [5][6][7][8] A large body of literature reports that cell behaviour, including growth, migration, proliferation, differentiation, and tissue formation are all strongly influenced by mechanical cues at the interface with the substrate on which the cells are cultured. ...
Hydrogels are commonly used materials in tissue engineering and organ-on-chip devices. This study investigatedthe nanomechanical properties of monolithic and multi-layered poly(ethylene glycol) diacrylate (PEGDA) hydrogels manufactured using bulk polymerisation and layer-by-layer projection lithography processes, respectively. An increase in number of layers (or reduction in layer thickness) from 1 to 8 and further to 60 results in a reduction in elastic modulus from 5.53 to 1.69 and further to 0.67 MPa, respectively. We also found that the decreasing number of layers induces a lower Creep Index (CIT) in 3D printed PEGDA hydrogels. This reduction was attributed to the mesoscale imperfections that appears as pockets of voids at the interfaces of the multi-layered hydrogels due to localised regions of unreacted prepolymer resulting in variations in defect density in the samples examined. An increase in the degree of crosslinking introduced by higher dosage of UV exposure leads to higher elastic modulus. This implies that the elastic modulus and creep behaviour of hydrogels are governed and influenced by the degree of crosslinking and defect density of the layers and interfaces. These finding can guide an optimal manufacturing pathway to obtain the desirable nanomechanical properties in 3D printed PEGDA hydrogels which are critical for the performance of living cells and tissues can be engineered through control of the fabrication parameters.
... It should be noted that the materials are not certified to be used as medical implants. Nevertheless, PEGDA is often used for 3D printing in scientific biomedical applications [6] and may be a promising candidate to be used for medical implants [7] [8]. However, biocompatibility of 3D printed implants from PEGDA-based photopolymer compositions need to be ensured in further research. ...
A new approach that offers the potential for local drug delivery to the inner ear is a 3D printed, patient individualized, drug-loaded implant that precisely fits into the round window niche (RWN). Anatomically correct digital light processing (DLP) 3D printed implant prototypes are beneficial for preoperative planning and rehearsal of implantation techniques due to tactile feedback. The aim is to define desired mechanical material properties for future RWN implants. For this purpose, RWN implant prototypes (RWN-IPs) were DLP 3D printed using commercially available E-Shell 500 and E-Shell 600 materials (Envisiontec GmbH, Gladbeck, Germany) and a selfestablished PEGDA700 composition. These photopolymers are suitable for 3D printing RWN-IPs that feature different mechanical characteristics. The (1) mechanical properties (tensile test) were investigated, (2) the implantation feasibility and (3) fitting accuracy in human cadaver RWN were evaluated. As a result, E-Shell 500 has relatively high stretchability (ɛm ~ 60%) while E-Shell 600 and PEGDA700 are brittle and PEGDA700 has low strength. The E-Shell 500 material performs by far the best at handling and insertion. EShell 600 has adequate strength but is hard to handle because of rigid material behavior. PEGDA700 enables high 3D printing accuracy but lacks adequate mechanical behavior for adequate insertion of implant prototypes in RWN.
... An interesting example among different hydrogels depicts poly(ethylene glycol) diacrylate (PEGDA). It is known to be non-toxic, hydrophilic and can be cured easily in the presence of UV light and the presence of a photoinitiator, such as the water-soluble and biocompatible lithium phenyl-2,4,6trimethylbenzoylphosphinate (LAP) [7,8]. It is extensively used in different studies, also 3D printing processes, which employ photopolymerization for the precise manufacturing of implants [2] or preparation of cell-or drug-loadedscaffolds [9,10]. ...
Hydrogels are 3D polymeric networks, which exhibit properties such as softness, viscoelasticity and their ability to absorb large amounts of water. These characteristics make them exceptionally suitable in biomedicine as e.g. tissue scaffolds, drug delivery systems, wound dressings or contact lenses. One of these hydrogels is the biocompatible, hydrophilic and photopolymerizable poly(ethylene glycol) diacrylate (PEGDA). It is used in different biomedical applications due to its tunable mechanical characteristics. In our study, the mechanical properties of different PEGDA hydrogel compositions with variyng molecular masses and contents of water/methanol, were investigated. Different compositions containing 20 m%, 30 m% or 40 m% of PEGDA 4K (4,000 g/mol), PEGDA 10K (10,000 g/mol) or PEGDA 20K (20,000 g/mol) in ultrapure water/methanol (1:2) were produced. Dumbbell-shaped samples were prepared in molds via photopolymerization in a UV chamber. Lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) was used as photoinitiator (0.5% w/w). The mechanical testing was performed using a uniaxial testing system. The obtained results showed averagely 78% higher tensile strength (σmax) values for 30 m% and 40 m% samples in comparison with 20 m% samples for all of the tested polymers. PEGDA 20K 30 m% samples showed the highest σmax among all of the samples with 12.8 MPa. All of the PEGDA20K samples exhibited the highest elongation at break (εB) values (up to 958%), whereas the lowest values were found for PEGDA 4K (up to 105%). The obtained stress-strain curves for most of the samples were typical for deformable, amorphous polymers with a deformation upon reaching a critical stress point. The PEGDA materials showed variable mechanical characteristics according to changing molecular mass or polymer concentration. These promising results showed that it should be possible to compose scaffolds with desired mechanical stability according to the needed application.
... In combination with a photoinitiator, polymerization is particularly versatile for tissue engineering [13]. Thus, spatially and temporally defined and highly complex structures can be 3D-printed from PEGDA to form 3D objects [14,15]. Furthermore, this material offers a wide range of different molecular weights that influence the material properties, such as stiffness, strength, swelling and diffusivity [15][16][17]. ...
... Thus, spatially and temporally defined and highly complex structures can be 3D-printed from PEGDA to form 3D objects [14,15]. Furthermore, this material offers a wide range of different molecular weights that influence the material properties, such as stiffness, strength, swelling and diffusivity [15][16][17]. The present study addresses the cited results by investigating the dependencies of different molecular weights of PEGDA with its material properties. ...
The aim of this case study is to generate several poly(ethylene glycol) diacrylate-based hydrogels using additive manufacturing process and compare their material properties. A commercial stereolithography system is used to produce the test specimens in accordance with ISO standards. Three formulations will be prepared for this purpose. The basis in each case is PEGDA with average molecular weights of 700 Mn, 575 Mn and 250 Mn. A photoinitiator and an UV absorber are added to ensure spatial and temporal crosslinking. Subsequently, the formulations are investigated for their material properties according to ISO standards by means of tensile, compression and hardness tests, and the influence of the molecular weights is determined.
