Stereolithography Resin Research Articles

A cross-linking strategy with moderated pre-polymerization of resin for stereolithography.

Compared with parts fabricated via traditional methods, such as injection or compression molding, polymeric parts produced by 3D stereolithography (SLA) have poorer mechanical properties. Here, we demonstrate a cross-linking strategy used in the coating field to attain long chains for resin pre-polymerization to obtain final resin parts which can expand the application of SLA. Isophorone diisocyanate (IPDI), 2-hydroxyethyl methacrylate (HEMA) and polyethylene glycol (PEG)-based prepolymer have long chains, making it easier for them to form dense structures. However, the prepolymer has high viscosity and can solidify in the absence of a laser. Thus, three kinds of adjuvants were added to dilute the prepolymer to make the slurry suitable for 3D-printing. Slurries were cured with different laser powers and scanning speeds. Diluents are found to affect the curing properties differently. With the diluent 2-hydroxyethyl acrylate added into the prepolymer, shrinkage of printed parts is lower than 1.3%. With the diluent ethylene glycol monophenyl ether, the density range of printed parts is between 1.187 g cm−3 and 1.195 g cm−3, which is higher than that of commercial PVC and PET. The three resins vary in density and hardness within a small range when the scanning speeds change. A relatively flat surface, high density and hardness can be obtained when the laser power is at 195.5–350 mW. Resin with this cross-linking strategy can expand the underutilized stereolithography's application from prototyping to actual parts by producing more functional components with excellent performance.

Antimicrobial modified hydroxyapatite composite dental bite by stereolithography

This study is aimed at the synthesis of antimicrobial hydroxyapatite (HAP)‐based composites for dental application by stereolithography (SLA). A micron‐sized commercial HAP was modified by methacrylate and quaternary ammonium salt, and, then, it was used in different amounts (namely 2.5, 5, and 10 wt%) as filler for a photocurable custom made resin for SLA. Thermal stability, microstructure, and particles size of the pristine (HAP) and modified HAP (mHAP) were evaluated by thermogravimetric analysis (TGA), X‐ray diffraction (XRD), and particle size analyser (CILAS). The suitability of each formulation for stereolithography process was assessed by measuring viscosity, degree of conversion (DC%) by Fourier transform infrared spectroscopy (FTIR), glass transition temperature, and thermal stability. Photo‐cured specimens for physical, mechanical, and antimicrobial testing were built by SLA. The flexural strength of the samples was measured using a 3‐point bending test method, and the fractured surface was analysed by scanning electron microscopy (SEM). The antimicrobial activity of samples was investigated against some standard microorganisms (Staphylococcus aureus, Escherichia coli, and Candida albicans), as representative Gram positive and Gram negative bacteria and fungus, respectively. The flexural strength increased with a filler content up to 5% and slightly decreased for higher content. SEM analysis confirmed the presence of uniformly distributed HAP. The incorporation of mHAP reduced the bacterial and fungal growth in dose‐dependent manner in comparison with the neat samples. Finally, a prototype of dental bite was built by SLA.

Preparation of a novel hybrid type photosensitive resin for stereolithography in 3D printing and testing on the accuracy of the fabricated parts

A novel hybrid type photosensitive resin for stereolithography in 3D printing was prepared with bisphenol A type epoxy diacrylate (EA-612), tripropylene glycol diacrylate (TPGDA), ethoxylated trimethyolpropane triacrylate(EO3TMPTA), cycloaliphatic diepoxide(ERL-4221), polycaprolactonepolyol(Polyol-0301),1-hydroxy-cyclohphenyl ketone(Irgacure184), and a mixture of triarylsulfonium hexafluoroantimonate salts (Ar3SSbF6). The novel hybrid type photosensitive resin was the photosensitive resin of an epoxy-acrylate hybrid system, which proceeded free radical polymerization and cationic polymerization in ultraviolet (UV) laser. Cuboid parts and double-cantilever parts were fabricated by using a stereolithography apparatus with the novel hybrid type photosensitive resin as the processing material, and the dimension shrinkage factor and the curl factor were tested. The shrinkage factor was less than 2.00%, and the curl factor was less than 8.00%, which showed that the accuracy of the fabricated parts was high with the photosensitive resin for stereolithography in 3D printing.

High-Strength Stereolithographic 3D Printed Nanocomposites: Graphene Oxide Metastability.

The weak thermomechanical properties of commercial 3D printing plastics have limited the technology's application mainly to rapid prototyping. In this report, we demonstrate a simple approach that takes advantage of the metastable, temperature-dependent structure of graphene oxide (GO) to enhance the mechanical properties of conventional 3D-printed resins produced by stereolithography (SLA). A commercially available SLA resin was reinforced with minimal amounts of GO nanofillers and thermally annealed at 50 and 100 °C for 12 h. Tensile tests revealed increasing strength and modulus at an annealing temperature of 100 °C, with the highest tensile strength increase recorded at 673.6% (for 1 wt % GO). Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) also showed increasing thermal stability with increasing annealing temperature. The drastic enhancement in mechanical properties, which is seen to this degree in 3D-printed samples reported in literature, is attributed to the metastable structure of GO, polymer-nanofiller cross-linking via acid-catalyzed esterification, and removal of intercalated water, thus improving filler-matrix interaction as evidenced by spectroscopy and microscopy analyses.

Reinforcement of Stereolithography Resin with Silica-Based Fillers

This study investigated the improvement of hardness and flexural properties of a commercial stereolithography (SLA) resin by reinforcement with silica-based fillers. Three types of fillers were studied: synthetic amorphous silica, milled fiberglass, and geothermal scale powder. Particle size and aspect ratio of fillers were estimated from scanning electron microscopy (SEM) images, while chemical structure was characterized by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. Fillers were added to SLA resin at 0, 10, and 20 vol%. Hardness and flexural properties of SLA composites are higher than unfilled resin. Moreover, both hardness and flexural properties of SLA composites are improved according to type (milled fiberglass > synthetic amorphous silica > geothermal scale powder) and loading (20 vol% > 10 vol%). The observed effect of filler type and loading on hardness and flexural properties of SLA composites is due to aspect ratio, intrinsic properties and dispersion of filler.

세 가지 방식으로 제작된 레진코핑의 내면적합성 평가: 3차원적 분석

Purpose: The purpose of this study was to evaluate the internal fitness of the resin coping that was fabricated by the traditional and Digital manufacturing methods through 3-dimensional analysis. Methods: maxillary right second molar was chosen implant master model. Custom-built impression trays were manufactured. After screwing the pick-up impression coping onto the master cast, impressions were made with silicone impression. The Working model was then made with type IV stone. The coping was fabricated: SLAC group (n=8), APPC group (n=8), LAPC group (n=8) Resin coping data was measured by using a three-dimensional evaluation program. Internal fitness was calculated by RMS (Root Mean Square).It measures mean and Standard Deviation (SD). Results: Three groups are measured 47.11±(3.08)㎛ total RMS of SLAC group, 48.35(±1.55㎛) for total RMS of LAPC group, 43.45±2.09㎛ for total RMS of APPC group. Measured value is gradually increased. Followed by autopolymerized pattern resin; Stereolithography resin, Light-activated pattern resin But there were no differences stastically(P>0.321). Conclusion: Evaluation of internal fitness on Resin copings was fabricated by three–ways methods showed that no differences statistically significant and clinically acceptable results

Development of CNTs-filled photopolymer for projection stereolithography

PurposePolymeric parts produced by 3D stereolithography (SL) process have poorer mechanical properties as compared to their counterparts fabricated via conventional methods, such as injection or compression molding. Adding nanofillers in the photopolymer resin for SL could help improve mechanical properties. This study aims to achieve enhancement in mechanical properties of parts fabricated by SL, for functional applications, by using well-dispersed nanofillers in the photopolymers, together with suitable post-processing.Design/methodology/approachCarbon nanotubes (CNTs) have high strength and Young’s modulus, making them attractive nanofillers. However, dispersion of CNTs in photopolymer is a critical challenge, as they tend to agglomerate easily. Achieving good dispersion is crucial to improve the mechanical properties; thus, suitable dispersion mechanisms and processes are examined. Solvent exchange process was found to improve the dispersion of multiwalled carbon nanotubes in the photopolymer. The UV-absorbing nature of CNTs was also discovered to affect the curing properties. With suitable post processing, coupled with thermal curing, the mechanical properties of SL parts made from CNTs-filled resin improved significantly.FindingsWith the addition of 0.25 wt.% CNTs into the photopolymer, tensile stress and elongation of the 3D printed parts increased by 70 and 46 per cent, respectively. With the significant improvement, the achieved tensile strength is comparable to parts manufactured by conventional methods.Practical implicationsThis allows functional parts to be manufactured using SL.Originality/valueIn this paper, an improved procedure to incorporate CNTs into the photopolymer was developed. Furthermore, because of strong UV-absorption nature of CNTs, curing properties of photopolymer and SL parts with and without CNT fillers were studied. Optimized curing parameters were determined and additional post-processing step for thermal curing was discovered as an essential step in order to further enhance the mechanical properties of SL composite parts.

New stereolithographic resin providing functional surfaces for biocompatible three-dimensional printing

Stereolithography is one of the most promising technologies for the production of tailored implants. Within this study, we show the results of a new resin formulation for three-dimensional printing which is also useful for subsequent surface functionalization. The class of materials is based on monomers containing either thiol or alkene groups. By irradiation of the monomers at a wavelength of 266 nm, we demonstrated an initiator-free stereolithographic process based on thiol-ene click chemistry. Specimens made from this material have successfully been tested for biocompatibility. Using Fourier-transform infrared spectrometry and fluorescent staining, we are able to show that off-stoichiometric amounts of functional groups in the monomers allow us to produce scaffolds with functional surfaces. We established a new protocol to demonstrate the opportunity to functionalize the surface by copper-catalyzed azide-alkyne cycloaddition chemistry. Finally, we demonstrate a three-dimensional bioprinting concept for the production of potentially biocompatible polymers with thiol-functionalized surfaces usable for subsequent functionalization.

A Novel Transmission Line Structure for High-Speed High-Density Copper Interconnects

This paper introduces a novel transmission line structure that can be employed in high-speed high-density copper interconnects, including both cables and connectors. The proposed structure uses a unique combination of dielectric materials with high and low permittivity values to decouple metal shields from adjacent signal pairs. In addition, the proposed structure employs an absorbing material to suppress any crosstalk resonances that may arise due to signal discontinuities in such highly dense environments. The optimum electrical properties of such an absorbing material in the proposed structure were determined using a simulation-based investigation. This paper also presents measured electrical properties of stereolithography resins suitable for rapid prototyping of high-speed interconnects. The effects of increasing the height of a connector on signal crosstalk and introducing any absorbing materials on signal loss are also discussed. Finally, this paper presents test boards and corresponding prototypes that were modeled and measured to validate the proposed transmission line structure for frequencies up to 40 GHz.

Structure-property relationship of nano enhanced stereolithography resin for desktop SLA 3D printer

Organically modified nanofillers, including nano SiO2, montmorillonite and attapulgite were loaded to stereolithography resin (SLR). The surface of nanofillers were modified using organic modifier of 3-(trimethoxysilyl)propyl methacrylate (γ-MPS) and (1-hexadecyl)dimethyl allyl ammonium chloride (C16-DMAAC), and were characterized by FTIR and small angle XRD analysis. The morphology of nanocomposites were observed by TEM. Viscosity and curing speed of SLR nanocomposites at increasing nanofillers loading were also studied. The mechanical properties of printed samples fabricated by a home-made stereolithography apparatus (SLA) 3D printer were tested. The influence of nanoparticles on the accuracy was measured and discussed. It was found that addition of 5% w/w of nano SiO2 increased the tensile strength and modulus by 20.6% and 65.1% respectively, and the printed accuracy was not significantly influenced. This study opens the way to the application of nanocomposites in the desktop level SLA 3D printing.

Novel photo-curable polyurethane resin for stereolithography

A novel photo-curable polyurethane resin for stereolithography has been demonstrated herein.

A stereolithographic resin pattern for evaluating the framework, altered cast partial removable dental prosthesis impression, and maxillomandibular relationship record in a single appointment

Fabricating a partial removable dental prosthesis usually requires 3 separate visits to evaluate the framework, altered cast impression, and maxillomandibular relationship record. This article describes an alternative technique for accomplishing each of these procedures in a single appointment with computer-aided design/computer-aided manufacturing (CAD/CAM) and rapid prototyping (RP) technologies.

Three-dimensional printed millifluidic devices for zebrafish embryo tests

Implementations of Lab-on-a-Chip technologies for in-situ analysis of small model organisms and embryos (both invertebrate and vertebrate) are attracting an increasing interest. A significant hurdle to widespread applications of microfluidic and millifluidic devices for in-situ analysis of small model organisms is the access to expensive clean room facilities and complex microfabrication technologies. Furthermore, these resources require significant investments and engineering know-how. For example, poly(dimethylsiloxane) soft lithography is still largely unattainable to the gross majority of biomedical laboratories willing to pursue development of chip-based platforms. They often turn instead to readily available but inferior classical solutions. We refer to this phenomenon as workshop-to-bench gap of bioengineering science. To tackle the above issues, we examined the capabilities of commercially available Multi-Jet Modelling (MJM) and Stereolithography (SLA) systems for low volume fabrication of optical-grade millifluidic devices designed for culture and biotests performed on millimetre-sized specimens such as zebrafish embryos. The selected 3D printing technologies spanned a range from affordable personal desktop systems to high-end professional printers. The main motivation of our work was to pave the way for off-the-shelf and user-friendly 3D printing methods in order to rapidly and inexpensively build optical-grade millifluidic devices for customized studies on small model organisms. Compared with other rapid prototyping technologies such as soft lithography and infrared laser micromachining in poly(methyl methacrylate), we demonstrate that selected SLA technologies can achieve user-friendly and rapid production of prototypes, superior feature reproduction quality, and comparable levels of optical transparency. A caution need to be, however, exercised as majority of tested SLA and MJM resins were found toxic and caused significant developmental abnormalities in zebrafish embryos. Taken together, our data demonstrate that SLA technologies can be used for rapid and accurate production of devices for biomedical research. However, polymer biotoxicity needs to be carefully evaluated.

Salt as a new colored solid model for simulation surgery.

Simulated craniomaxillofacial surgery is critical for planning the procedure, shortening operative time, and practicing the procedure. However, typical models are expensive, given their solid materials, and the surgical sensations do not accurately reflect the procedure performed using human bone. To solve these problems, a new solid salt model has been developed. Stereolithography data was generated using computed tomography data, and a salt model was created using a 3D inkjet printer. By extracting specific data for elements such as the teeth and mandibular canal, these elements were highlighted in the solid model using different colored material. Also, we compared the maximum load and plastic deformation of the salt model, a stereolithographic resin model, and a pig limb. The salt model had similar tenacity to bone, and the risk of damage to the teeth and inferior alveolar nerve was easily confirmed. The material cost of the salt model is extremely low, and the salt model may provide a more accurate sensation of cutting human bone. Thus, this model is useful for both simulated operation and practice for inexperienced surgeons.

Effects on Cell Differentiation and Cell Survival Rate of the Photocurable Resins for Stereolithography

Effects on Cell Differentiation and Cell Survival Rate of the Photocurable Resins for Stereolithography

Towards a Novel, Implantable Limb Lengthening Device1

Several surgical techniques and devices have been developed to help patients born with limb deformities, limb length inequalities, and extreme short stature. People with such ailments often experience pain, dysfunction, and joint degeneration. The primary method of treating such deformities is an osteotomy followed by callus distraction [1]. Commonplace lengthening devices are external fixators and intramedullary devices, but each has its drawbacks. Traditional external fixators, such as the Ilizarov device and Taylor spatial frame, are cumbersome, painful, and produce large residual scars [2]. Due to pin tract infection rates of 10–20%, lengthening with these methods requires careful surveillance [3]. Intramedullary lengthening devices can cause severe complications such as intramedullary infection [4]. Surgeons have recently experienced success with a motorized, intramedullary nail (Fitbone), but pediatric use of this device can be limited due to interference with open growth plates [5]. The investigators have designed an extramedullary device that retains the attractive qualities of an intramedullary nail, without the risk of deep infection or damage to growth plates. Additionally, the device can be equipped with a six-axis force-torque sensor capable of measuring forces and moments in real time.

Development and characterization of novel photopolymerizable formulations for stereolithography

Abstract Novel photopolymerizable formulations, able to photopolymerize with a dual mechanism (cationic and radical), were developed and characterized as potential resins for stereolithography (SL) process. The influence of the presence of organically modified boehmite nanoparticles on the properties of the photopolymerizable mixtures was also analyzed. The main properties required for a liquid SL resin are a high reactivity and a low viscosity. All of the experimental formulations produced, even in the presence of boehmite nanoparticles, are able to satisfy these significant requirements. Physical-mechanical and thermal properties of the photocured samples, obtained starting from the experimental formulations, were finally measured. The cured nanocomposite bars show a high transparency, confirming the good dispersion of the nanofiller in the polymeric matrix and possess improved glass transition temperature (Tg) and mechanical performances, compared to the unfilled system and to a commercial stereolithographic resin. These results suggest the possibility of using the novel nanofilled photopolymerizable suspensions in the stereolithographic apparatus to build, not only esthetical, but also functional prototypes.

Acrylic-based Stereolithographic Resins: Effect of Scaffold Architectures on Biological Response

Stereolithography (SL), one of rapid prototyping techniques, has many advantages over other methods in fabrication of three dimensional objects, particularly those used in biomedical fields. Various complex medical objects, especially scaffold, can be precisely custom-constructed using this technique. This research aims to evaluate the effect of different scaffold architectures, fabricated with photosensitive liquid polymer using SL technique, on cell responses in terms of cell proliferation and alkaline phosphatase (ALP) activity. A variety of difunctional and trifunctional (meth)acrylate resin formulations were evaluated for mechanical strength by three-point bending using Universal Testing Machine. Volume shrinkage for each formulation was also investigated. The most promising resin composition for stereolithography technique that exhibited good mechanical strength and low shrinkage was chosen for scaffold fabrication. Five scaffold architectures with different percentages of porosity, designed by computer-aided design program (CAD), were successfully fabricated to microscale scaffolds using stereolithography apparatus equipped with UV laser source. Microscale images of stereolithographic-fabricated scaffolds were observed under a scanning electron microscope (SEM). Alamar blue and alkaline phosphatase assays were used to investigate biological responses of scaffolds. The results revealed that no significant difference in cell proliferation for all patterns after 21-day culture period whereas a lower porous scaffold exhibited a greater ALP activity. 

Rapid bonding of polydimethylsiloxane to stereolithographically manufactured epoxy components using a photogenerated intermediary layer

We describe a low cost, photo-induced, room-temperature bonding technique for bonding epoxy components to flexible PDMS membranes in less than half an hour. Bond strengths (~350 kPa) were characterized by ISO-conform tensile testing for a popular stereolithography resin and found comparable bond strengths as reported for PDMS/PDMS bonds.

Rapid Prototyping Techniques for Prototyping and Research of Polymer Gear Transmissions

The article presents different fields of usage of Rapid Prototyping techniques in production and research of functional prototypes of polymer gears for electromechanical industry. Such Rapid Prototyping techniques as stereolithography and vacuum casting are used for preparing of functional prototypes of gears. The method of receiving of accurate gears made of differ plastics is shown. The gears are made by duplication of the stereolithographic model in the silicon matrices. The properties of stereolithographic resin are used in order to photo-elastic research - the determination of distribution of stresses in the gears of loaded transmission. The deformations of teeth of loaded transmission are frozen using vacuum casting. Beside the deformations, the tooth contact on the flank surfaces of teeth is obtained. The tooth contact can be also directly observed when the test gears are made of transparent plastic. The usefulness of Rapid Prototyping for production of accuracy gears and the usefulness of vacuum casting for freezing deformation and observation of tooth contact is shown in the conducted research. The presented solutions can be applied to the plastic gears. The presented possibilities of production and research of polymer gears can find a wide application in the electromechanical industry, that produced gears for drives of different types of devices, for example in the household equipments, in the motorization. The novelty is the usage of vacuum casting for freezing deformations of teeth in the static load transmission. The method allows preliminary verification of correctness of construction of gears basis of the received tooth contact - its size and location on the tooth flank.