Application Of Stereolithography Research Articles

Poly(ethylene‐glycol)‐Dimethacrylate (PEGDMA) Composite for Stereolithographic Bioprinting

AbstractRecent progress in additive manufacturing has enabled the application of stereolithography (SLA) in bioprinting to produce 3D biomimetic structures. Bioinks for SLA often require synthetic polymers as supplements to ensure the structural integrity of the printed cell‐laden constructs. High molecular weight (MW) poly(ethylene‐glycol)‐diacrylate (PEGDA) (MW ≥ 3400 Da) is commonly used to enhance the mechanical property of crosslinked hydrogels. However, the production of bioink with high MW PEGDA requires in‐house polymer synthesis or the acquisition of costly reagents, which may not be readily available in all laboratory settings. As an alternative to high MW PEGDA, this research investigated the use of poly(ethylene‐glycol)‐dimethacrylate (PEGDMA) (MW = 1000 Da) as a supplement of a bioink to enhance the mechanical properties of the SLA‐printed constructs. The successful demonstration showcases 1) the fabrication of 3D constructs with overhang and complex architecture, and 2) the cytocompatibility, with high cell viability of 71–87% over 6 days of culture, of the GelMA‐PEGDMA bioink to enable cell‐laden bioprinting. This study suggests PEGDMA as a viable supplement in the formulation of SLA bioink. The accessibility to PEGDMA will facilitate the advance in 3D bioprinting to fabricate complex bioinspired structures and tissue surrogates for biomedical applications.

Osteosarcoma growth on trabecular bone mimicking structures manufactured via laser direct write

 This paper describes the direct laser write of a photocurable acrylate-based PolyHIPE (High Internal Phase Emulsion) to produce scaffolds with both macro- and microporosity, and the use of these scaffolds in osteosarcoma-based 3D cell culture. The macroporosity was introduced via the application of stereolithography to produce a classical “woodpile” structure with struts having an approximate diameter of 200 μm and pores were typically around 500 μm in diameter. The PolyHIPE retained its microporosity after stereolithographic manufacture, with a range of pore sizes typically between 10 and 60 μm (with most pores between 20 and 30 μm). The resulting scaffolds were suitable substrates for further modification using acrylic acid plasma polymerisation. This scaffold was used as a structural mimic of the trabecular bone and in vitro determination of biocompatibility using cultured bone cells (MG63) demonstrated that cells were able to colonise all materials tested, with evidence that acrylic acid plasma polymerisation improved biocompatibility in the long term. The osteosarcoma cell culture on the 3D printed scaffold exhibits different growth behaviour than observed on tissue culture plastic or a flat disk of the porous material; tumour spheroids are observed on parts of the scaffolds. The growth of these spheroids indicates that the osteosarcoma behave more akin to in vivo in this 3D mimic of trabecular bone. It was concluded that PolyHIPEs represent versatile biomaterial systems with considerable potential for the manufacture of complex devices or scaffolds for regenerative medicine. In particular, the possibility to readily mimic the hierarchical structure of native tissue enables opportunities to build in vitro models closely resembling tumour tissue.

Transforming stereolithographic prototypes into metal or ceramic models by polymer substitution with titanium powder

The presented paper experimentally demonstrates the potential expansion of stereolithographic prototype utilization. Two methods for manufacturing plastic prototypes are proposed, enabling the subsequent substitution of the polymer material with either metal or ceramics. The first method involves additional actions by the prototype designer during the modeling stage. The second method necessitates alterations in the technological processes of model preparation and prototype manufacturing using a stereolithography apparatus. Material substitution occurs in two stages. Initially, cavities in the prototype are filled with powder material or a mixture of powder and water. Although titanium powder was chosen as the test material, the proposed technology permits the utilization of a broad spectrum of powder materials, encompassing both metallic and ceramic options. The subsequent stage involves heat treatment, where the polymer is eliminated, and the metal powder is sintered while retaining the original shape and dimensions of the prototype. Heat treatment of the acquired prototypes was conducted in both argon and atmospheric air environments. The utilization of different gas media might induce chemical transformations in the material filling the prototype. The experiments lead to the conclusion that the proposed approaches show promise and merit further development. Additionally, we contemplate amalgamating the two methods in the future to attain an optimized final outcome. The data we have gathered could significantly contribute to broadening the scope of stereolithography applications, given that this technology presently represents one of the most precise, widespread, and accessible additive manufacturing methods.

Influence of Post-Processing and the Type of Filling on Strength Properties of Elements Printed by Stereolithography Technology

The application of stereolithography, gives the possibilities to manufacture components with complex shape, during one continuous process based on the prepared virtual model in CAD system. The paper presents the results of experimental tests for samples printed using Low Force Stereolithography (LFS)TM technique, using Rigid 4000 Resin, Formlabs company. The experimental studies used unconventional post-processing, which consists in extending the exposure to UV lamps, without the application of heating. In the next step, optimized post processing parameters were used to manufacture components with different types and degrees of filling - linear and hexagonal. In the experiment, the samples were testes to a tensile strength test and a three-point bending test. The goal of the experiment was to select optimal parameters for post-processing and element design to reduce the component weight.

Physics-Informed Neural Networks (PINNs) for Improving a Thermal Model in Stereolithography Applications

Stereolithography (SLA), additive manufacturing (3D printing) technique, is widely used nowadays for rapid prototyping and manufacturing (RP & M). This technique is driven by photo-polymerisation, which is an exothermal process. This may lead to thermal stresses significantly affecting the final quality of printed parts/products. To guarantee high-quality parts printed with the SLA technique, understanding the thermal behaviour is therefore crucial for optimizing the process. In this paper, the recent physics-informed neural network (PINN) methodology was employed to improve a physics-based model for predicting the thermal behaviour of SLA processes. The accuracy of the improved thermal model is demonstrated in this paper by comparing the predicted 2D temperature field with the 2D temperature field measured by a high-speed infrared thermal camera on parts printed on a production machine.

Application of Stereolithography Based 3D Printing Technology in Investment Casting.

Advanced methods for manufacturing high quality parts should be used to ensure the production of competitive products for the world market. Investment casting (IC) is a process where a wax pattern is used as a sacrificial pattern to manufacture high precision casting of solid metal parts. Rapid casting is in turn, a technique that eases the IC process by combining additive manufacturing (AM) technologies with IC. The use of AM technologies to create patterns for new industrial products is a unique opportunity to develop cost-effective methods for producing investment casting parts in a timely manner. Particularly, stereolithography (SLA) based AM is of interest due to its high dimensional accuracy and the smooth surface quality of the printed parts. From the first appearance of commercially available SLA printers in the market, it took a few decades until desktop SLA printers became available to consumers at a reasonable price. Therefore, the aim of this review paper is to analyze the state-of-the-art and applicability of SLA based 3D printing technology in IC manufacturing, as SLA based AM technologies have been gaining enormous popularity in recent times. Other AM techniques in IC are also reviewed for comparison. Moreover, the SLA process parameters, material properties, and current issues are discussed.

Synthesis of an UV-Curable Divinyl-Fumarate Poly-ε-Caprolactone for Stereolithography Applications.

The limited number of commercially available photocrosslinkable resins for stereolithography has often been considered the main limitation of this technique. In this manuscript, a photocrosslinkable poly-ε-caprolactone (PCL) has been synthesized by a two-step method starting from ring opening polymerization (ROP) of ε-caprolactone. Hydroxyethyl vinyl ether (HEVE) has been used both as the initiator of ROP and as photo-curable functional group to obtain a vinyl poly-ε-caprolactone (VPCL). The following reaction of VPCL with fumaryl chloride (FuCl) results in a divinyl-fumarate polycaprolactone (VPCLF). Moreover, a catalyst based on Al, instead of the most popular Tin(II) 2-ethylhexanoate, has been employed to reduce the cytotoxicity of the material. VPCLF has been successfully used, in combination with N-vinyl-pyrrolidone (NVP), to fabricate 3D porous scaffolds by micro-stereolithography (μ-SL) with mathematically defined architectures.

Role of an Orthodontist in the Management of Cleft Maxilla With Anterior Maxillary Segmental Distraction (AMD)- A Clinical overview

The main clinical and radiological defect in cleft maxilla is localised at the region of nasomaxillary complex and thereby the increased focus on maxillary interventional correction. During the period of development, the affected individual undergoes a series of periodic treatment approaches aimed towards normalisation of the function and aesthetics. However, such interventional procedures can have otherwise effects on the restriction of growth. Surgical and facial orthopaedic interventions can cause protrusion of the premaxilla. This influences the depth and height of the upper jaw and thus the total height causing clockwise rotation of the face. Similarly, the depth of the posterior maxilla is found to be reduced in CLP cases. The advancement of the anterior maxilla with callus distraction for correction of the cleft maxilla was first reported by KraKasis and Hadjipetrou in 2004. The technique has been used since then with variable success and less predictability. The present table clinic is targeted to showcase the key features of various stages critical in planning the anterior maxillary distraction in adult maxillary hypoplasia cases. The requirement of precision in planning and treatment is high in such cases to minimize the adverse effects. The novel methodology discussed here is the combination of CBCT, face bow transfer and stereolithography for surgical planning and simulation. With the use of CBCT diagnostic capacity is enhanced, enabling visualisation of the defect. It also helps to simulate surgical procedure virtually and/or with the application of stereolithography. Use of the face bow facilitates biomechanical planning. The registration of the maxillomandibular relation to the cranial base serves as a guide to position the distractor. This is a critical step, as it dictates the direction of the distraction force vectors. Precise orientation and planning enable predictable movement of the anterior maxilla and control the extent of anterior open bite opening, in most cases. This contrasts with the overbite created with counter clockwise jaw rotation, reducing the post distraction orthodontic management. This table clinic presentation also draws home the key points in identifying and mitigating the potential complications during and after the distraction. The use of the present methodology enables a predictive treatment outcome for the cases with minimal complications associated with distraction with a marked reduction in the magnitude of callus molding. Therefore, with the application of this novel clinical paradigm for AMD, a predictable result can be achieved, which helps in the reduction of the treatment time and gives a stable outcome

Dispersion and properties of zirconia suspensions for stereolithography

AbstractStereolithography is an attractive technique for the fabrication of complex‐shaped ceramic components with high dimensional accuracy. One of the challenges in this technology is the development of high solid loading, low viscosity photosensitive ceramic suspension. In this study, the dispersion of zirconia in photocurable resin and the slurry properties were intensively investigated. Rheological measurements showed that DISPERBYK‐103 proved to be an effective dispersant. 42 vol% ZrO2suspension was successfully prepared using 3.5 wt% DISPERBYK‐103 as the dispersant, with a suitable viscosity (4.88 Pa·s) below the maximum allowable viscosity value (5 Pa·s) for stereolithography applications. The adsorption behavior of DISPERBYK‐103 on the surface of zirconia powders was characterized by TG and FT‐IR, confirming the dispersion effect of dispersant. Contact angle measurements were also conducted to show that the adsorption of DISPERBYK‐103 could help to improve the wettability between powder and photocurable resin. Results showed that DISPERBYK‐103 was effective for the preparation of suitable slurries for the development of ZrO2ceramics through stereolithography.

Medical applications of stereolithography: An overview

Stereolithography or three-dimensional printing (3DP) is a fast-growing field, with increasing number of health-care applications. As an industry, stereolithography is expected to grow from an estimated $700 million to nearly $9 billion in revenue over the next few years, mainly due to continued advancements and practical implementations of the technology. More established applications of 3DP in medicine involve the creation of wearable assist devices, prosthetics, and orthotics. Research is ongoing in the area of incorporating biologic (including genetic) implementations of 3DP technology, with the long-term goal of three-dimensional printing of organs and tissues that can be subsequently implanted into human body. Given that applications of 3DP in health-care have only recently begun to proliferate, there continues to be paucity of literature in this important and rapidly evolving area of research. In the current review, we sought to present a comprehensive and most current high-level overview of 3DP, with the goal of catalyzing better general understanding and promoting research in 3DP for biomedical applications. The following core competencies are addressed in this article: Medical knowledge, Systems-Based Practice.

Study of the Solidification Dynamic of a Photocurable Resin by Photoacoustic

This paper reports on the photoacoustic (PA) study of a photopolymer (resin) that changes its physical properties when being irradiated with ultraviolet light from a xenon lamp. The wavelength range necessary for the curing of the resin, characterized by the PA technique, was found to be between 300 nm and 400 nm. PA measurements show a sigmoidal change of heat transport properties as a function of time during the curing process. By describing the PA signal evolution by a parametrized model, a characteristic curing time was introduced. The PA measurements were complemented with UV–Vis Spectroscopy, which was used to characterize the polymer in order to study the optical absorption. The proposed method can support the optimization of the settings of curing parameters in applications of stereolithography and 3D printing.

Surface functionalization of acrylic based photocrosslinkable resin for 3D printing applications

The limited number of resins, available for stereolithography applications, is one of the key drivers in research applied to rapid prototyping. In this work an acrylic photocrosslinkable resin based on methyl methacrylate (MMA), butyl methacrylate (BMA) and poly(ethylene glycol) dimethacrylate (PEGDA) was developed with different composition and characterized in terms of mechanical, thermal and biological behaviour. Two different systems have been developed using different amount of reagent. The influence of every components have been evaluated on the final characteristic of the resin in order to optimize the final composition for applications in bone tissue engineering. The crosslinked materials showed good mechanical properties and thermal stabilities and moreover cytotoxicity test confirms good biocompatibility with no cytotoxic effect on cells metabolism. Moreover two different treatments have been proposed, using fetal bovine serum (FBS) and methanol (MeOH), in order to improve cell recognition of the surfaces. Samples threatened with MeOH allow cell adhesion and survival, promoting spreading, elongation and fusion of C2C12 muscle myoblast cells.

Evaluation of thiol-ene photo-curable resins using in rapid prototyping

Purpose The purpose of this paper is to evaluate the properties of several thiol-acrylate photosensitive systems and compare with corresponding acrylate free-radical systems. The potential stereolithography applications of thiol–ene photosensitive systems are also discussed. Design/methodology/approach In the both thiol–ene and acrylate free-radical photosensitive systems, various key performances were characterized. The function group conversions were characterized by real-time Fourier transform infrared spectroscopy. The tension strength was determined according to the standard ASTM D638-2003, the flexible strength was determined according to ASTM D790-07 and the hardness was measured according to ASTM D2240-05. The volume shrinkage was measured by dilatometer method. The glass transition temperature was analyzed by differential scanning calorimeter. Findings As adding mercapto propionates into acrylate system, the inhibition of polymerization by oxygen was controlled and the flexible performance was improved. In addition, the photosensitive resin showed better tension strength, higher elongation at break and lower volume shrinkage. Among the four mercapto propionates, rigid TEMPIC showed most obvious affect, followed hexa-functional DPMP, tetra-functional PETMP and tri-functional TMMP. Originality/value Although the thiol–ene photosensitive resin has unmatched advantages in performance, there are no reports on the thiol–ene photosensitive resin in the stereolithography application. In this study, thiol–ene photopolymerization material was first tentatively implemented in stereolithography area. Several critical performance parameters were compared between thiol–ene and acrylate free-radical photosensitive systems.

Synthesis of photocrosslinkable divinyl-fumarate poly-epsilon-caprolactone for stereolithography applications

Synthesis of photocrosslinkable divinyl-fumarate poly-epsilon-caprolactone for stereolithography applications

UV-LED를 이용한 광조형 장치 개발

The stereolithography(SL) process is a type of fabrication technology which relies on photopolymerization. It has a relatively simple fabrication process and a resolution of several tens of <TEX>${\mu}m$</TEX>. Recently, SL technology has been applied to various areas, such as bioengineering and MEMS devices, due to the development of advanced materials. This technologycan be divided intothe scanning(SSL) and projection (PSL) types. In this paper, in stereolithography, parts are fabricated by curing photopolymeric resins with light. The application of stereolithography can now include fabricated parts. This process, called stereolithography, can fabricate parts by taking into account theirdegrees of geometry complexity. In particular, UV-LED stereolithography can perform quite rapid fabrication in which specific cross-sections are cured upon exposure to light.

Exposure Time Variation Method Using DMD for Microstereolithography

In stereolithography, parts are fabricated by curing photopolymeric resins with light. The application of stereolithography can now be extended to a very small scale. The process, called microstereolithography, can fabricate parts on a microscale without any further consideration of geometry complexity. In particular, projection-type microstereolithography can perform quite rapid fabrication that cures a specific cross section in one exposure to light without movement. However, in the case where the light source has a nonuniform intensity or an aberration caused by its optics, the part might have some distortion, and this is commonly the case. Because the material experiences shrinkage when it is cured, the light intensity over the entire cross section should be uniform. This study utilizes a Dynamic Mirror Device, which is mainly used for beam shaping, to control the beam intensity also. This control makes the beam intensity profile flat and reduces the distortion to a great degree. This paper presents the concept of an exposure time control method that makes the beam intensity uniform, and it also presents some experimental results.

High solids loading ceramic colloidal dispersions in UV curable media via comb-polyelectrolyte surfactants

Ceramic articles and ceramic/polymer composites with complex 3d shapes can be produced by rapid prototyping techniques such as stereolithography of ceramic dispersions in UV curable resins. Nanometer and submicrometer ceramic particles are advantageous for high resolution microstructures, surface quality and reduced sintering temperatures. Frequently, special surfactants are needed to maximize solids loading while maintaining suitable rheological properties for stereolithography applications (viscosity <5 Pa s, 30 1/s). We present here a general scheme for relatively high loading/low viscosity dispersions of nanometer and submicrometer particles in UV curable resins using comb-polyelectrolyte surfactants. In the present approach, adsorption is favorably carried out in aqueous media and the dry particles with adsorbed surfactant are transferred to the organic media through centrifugation, washing, drying and dry milling. The method is demonstrated for Al 2O 3, ZnO and mixed Al 2O 3/ZnO colloidal dispersions. Dispersions containing >48 vol% particles suitable for stereolithography have been achieved. Dispersions containing 36 vol% particles are predicted to have viscosities in the range suitable for direct inkjet printing applications at 75 °C. The particle stabilization and transfer schemes, rheological behavior and UV curing characteristics are presented.

Highly loaded UV curable nanosilica dispersions for rapid prototyping applications

Silica microcomponents are attractive for applications requiring high temperature stability and chemical durability such as in microreactors. Rapid prototyping methods of forming ceramic dispersions hold great potential for manufacturing of microreactors. Stereolithography for example can benefit from highly solid loaded, low viscosity and high transparency dispersions. This article presents the development of >40 vol.%, UV curable transparent silica nanodispersions having viscosities suitable for stereolithography applications. The main parameters enabling these high loading dispersions are minimization of the Van der Waals attractive forces and affinity of monomer end group for the silica surface (e.g. hydrogen bonding). The minimization of the Van der Waals attraction is achieved by refractive index matching of the nanosilica and UV curable acrylate monomers. This results also in highly transparent dispersions having curing depths in the order of 10 mm in the UVA range. The transformation of selected dispersions to self-supporting silica glass sheets through UV curing, debinding and sintering was investigated by TGA/DTA, dilatometry and XRD.

Tissue Engineering of Vascular Conduits: Fabrication of Custom-Made Scaffolds Using Rapid Prototyping Techniques

The technique of stereolithography, which automatically fabricates models from X-ray computed tomography or magnetic resonance imaging (MRI) data linked to computer-aided design programs, has been applied to the fabrication of scaffolds for tissue engineering. We previously reported on the application of stereolithography in scaffold fabrication of a trileaflet heart valve. In our current experiment we demonstrate a new technique for the fabrication of custom-made conduits for the potential replacement of a coarcted aortic segment. In this experiment the image data derived from a 12-year-old male patient with aortic coarctation scanned by MRI were processed by a computer-aided design program to reconstruct the aortic arch with isthmus stenosis three dimensionally. By defining the stenotic section and the adjacent normal vessel a custom-made nonstenotic descending aorta was reconstructed to replace the stenosed part. The rapid prototyping technique was used to establish stereolithographic models for fabricating biocompatible and biodegradable vascular scaffolds with the anatomic structure of the recalculated human descending aorta through a thermal processing technique. Our results suggest that the re-creation and reproduction of complex vascular structures by computer-aided design techniques may be useful to fabricate custom-made polymeric scaffolds for the tissue engineering of living vascular prostheses.

Application of Stereolithography to Chemical Engineering: ‘From Macro to Micro’

The accuracy of the conventional stereolithography process has been improved to shape microstructures, especially for chemical engineering applications. Thus, a new recoating system has been developed to allow the deposition of resin or suspension layers with thickness ranging from 5 to 40 μm. Moreover, the influences of photomaterial formulation and of oxygen inhibition have been discussed with regard to polymerization kinetics and process accuracy. As a consequence, lateral and vertical resolutions of conventional stereolithography have been improved to 50 and 5 μm respectively. Finally, microstructures such as microtransducers, micropumps and heat exchangers have been created by stereolithography. As a result, the contribution of these microstructures to process intensification and local control has to be considered.