Stereolithography 3D Printing Technology Research Articles

A non-uniform lattice design method for lightweight structures in 3D printing

Lightweight design is an essential topic in aerospace, automotive and other fields. In automobile manufacturing, the engine connecting rod is one of the main components; its lightweight design has a high reference value. And 3D printing provides a feasible solution for designing and manufacturing lightweight structures. Unlike the traditional geometrically homogeneous point design, this study offers a non-homogeneous point design method based on the spatial stress state of additively manufactured components. After numerical simulation of quasi-static stresses on a model of an engine connecting rod, finite element grid cells with different stress values are replaced by lattice cells with different specific stiffnesses at similar local stress levels. The overall specific stiffness of the structure is further improved by continuing the optimized design with the corresponding gradient-type reinforcement of the non-uniform lattice structure. The basic idea of this design is to perform non-uniform adaptive filling of solid parts under localized loading by employing different types of unit cells. Stereolithography 3D printing technology prepares the engine lattice structural parts for quasi-static compression comparison experiments and fracture analysis after failure. The conclusions show that the engine connecting rod members with non-homogeneous lattice have more excellent overall mechanical properties than homogeneous lattice members. This work demonstrates the feasibility of such design methods for 3D printing lightweight structures and optimization.

Influences of two sizes of nano-Fe3O4 on stereolithography 3D printing properties of gel photoresist for photothermal-responsive hydrogel

Nanocomposite hydrogels enable augmented properties, functions, and responsive behaviors. In the field of stereolithography 3D printing of the photothermal responsive nanocomposite hydrogel, the influence of the size of nano-Fe3O4 on 3D printing properties is significant due to the sedimentation, but the relevant research is rare. In this study, for the fabrication of photothermal responsive hybrid hydrogel, poly(N-isopropylacrylamide-acrylamide)/nano-Fe3O4 [P(NIPAM-AM)/nano-Fe3O4] gel photoresist was prepared and digital light processing (DLP)-based 3D printing as one of the popular stereolithography 3D printing technology was utilized. The influences of two sizes of Fe3O4 nanoparticles (10 and 50 nm) denoted as nano-Fe3O4(10) and nano-Fe3O4(50) on DLP 3D printing properties of the gel photoresist were investigated in detail. The results reveal that the gel photoresist with nano-Fe3O4(10) obtained long exposure time for the basic prototype, low overcuring degree (Od), and good uniformity of nanoparticles in hybrid hydrogels, while those with nano-Fe3O4(50) had the merits of printing high 3D sample due to the low release fore. Unfortunately, the gel photoresist with a high content of nano-Fe3O4 such as 3.11 wt% failed in 3D printing of a high and uniform gel cylinder. A strategy of preparing P(NIPAM-AM)/nano-Fe3O4 gel photoresist with mixed nano-Fe3O4(10) and (50) for 3D printing was proposed. Using the gel photoresist (nano-Fe3O4 content: 3.11 wt%) with two sizes of nano-Fe3O4 mixed with 50% each and the exposure time of 8 s, a gel cylinder with a height of 1 cm was successfully printed with uniform nano-Fe3O4 distribution and low Od values (≤ 1.17%). Further, a biomimetic hydrogel octopus was 3D printed by using the gel photoresist with mixed nano-Fe3O4 and thereafter a near-infrared-light-driven waving motion of octopus tentacle was achieved successfully.

3D printing of high-purity complex SiC structures based on stereolithography

Complex Silicon carbide (SiC) structures are hardly achievable via traditional manufacturing methods, while stereolithography 3D printing technology effectively shapes sophisticated structures with high precision. However, it is a huge challenge to prepare SiC slurry for stereolithography 3D printing with excellent curing ability due to the increased light absorption of SiC powder. Therefore, a novel approach to fabricating high-purity SiC structures is proposed in this study based on the stereolithography 3D printing process, where SiO2 powder is used as an additive to increase the curing thickness from 27.8 μm to 53.0 μm. Moreover, phenolic epoxy resin (PEA) is introduced as a carbon source to transform SiO2 to SiC during sintering. As a result, there is almost no SiO2 phase or SiOC remaining in the final parts when the addition of PEA reaches 50 wt% related to the resin weight after sintering at 1600 °C for 4 h. Based on the SiC/SiO2/PEA slurry systems prepared, high-purity silicon carbide with complex structures can be successfully fabricated in one step without any pre-oxidation or precursor impregnation processes. This approach provides valuable insights into additive manufacturing of high-purity complex SiC structures.

Innovative ceramic paste for stereolithography additive manufacturing alumina core applied in turbine blade casting

AbstractCeramic stereolithography 3D printing technology has demonstrated great potential in alumina core manufacturing for advanced turbine blade casting. However, there have been very few photosensitive material formulas specifically designed for alumina core fabrications. Herein, we present the design of a 3D printable ceramic paste based on bimodal particle size distributions for additive manufacturing of high‐quality alumina cores. The coarse particles in the paste remain in their original shape while the fine particles transform into platelet‐like particles during sintering. The effects of coarse particles, platelet‐like particles, and grain growth on maintaining porosity and limiting shrinkage rates are studied. Furthermore, the vacuum sintering process is found to be beneficial for core material properties. The physical properties tests verify that the newly designed alumina paste in this work can meet the application requirement, which is superior to the previous research.

Design and formation mechanism of in-situ synthesis YAG sintered necks in stereolithography 3D printed Al2O3-based ceramic cores

The intricate structure of ceramic cores is crucial in producing high-temperature-resistant hollow blades. Traditional techniques for ceramic cores preparation, such as hot injection, rely heavily on moulds, thus limiting the production of complex structures in ceramic cores. Stereolithography 3D printing technology provides a novel approach to creating these cores, leveraging its precision and model customization capabilities. However, issues like the challenge of effectively controlling both porosity and strength hinder its widespread adoption. In this study, high-performance ceramic cores reinforced with in-situ YAG were successfully prepared by adding Y2O3 using stereolithography 3D printing technology. Thorough thermodynamic calculations for Y2O3 incorporation into Al2O3-based ceramic cores were systematically analysed, revealing the formation of Y3Al5O12 (YAG) at elevated temperatures due to Y2O3 and Al2O3 interaction. Subsequently, the variations in microstructure and properties were investigated across different temperatures. Due to diffusion, YAG sintered necks and cohesive framework were formed on the surface of Y2O3, resulting from the reaction between Y2O3 and Al2O3. YAG sintered necks and Y2O3 effectively inhibited crack deflection. The high degree of densification of the in-situ generated YAG and cohesive framework improved the mechanical properties; meanwhile, the presence of porosity between YAG and Al2O3 contributed to the enhancement of porosity. The cores exhibited exceptional mechanical properties at 1823.15 K. The open porosity was 30.08%. The flexural strengths were 41.2 MPa (298.15 K) and 32.0 MPa (1773.15 K). The design of YAG sintered necks by adjusting the sintering temperature introduced a new idea for synergistically adjusting porosity and strength. The advancement is anticipated to improve the production of intricately structured ceramic cores with superior performance.

Analysis of Covarine Particle in Toothpaste Through Microfluidic Simulation, Experimental Validation, and Electrical Impedance Spectroscopy.

Covarine, copper phthalocyanine, a novel tooth whitening ingredient, has been incorporated into various toothpaste formulations using diverse technologies such as larger flakes, two-phase pastes, and microbeads. In this study, we investigated the behavior of covarine microbeads (200 μm) in Colgate advanced white toothpaste when mixed with artificial and real saliva. Our analysis utilized a custom-designed microfluidic mixer with 400 μm wide channels arranged in serpentine patterns, featuring a Y-shaped design for saliva and toothpaste flow. The mixer, fabricated using stereolithography 3D printing technology, incorporated a flexible transparent resin (Formlabs' Flexible 80A resin) and PMMA layers. COMSOL simulations were performed by utilizing parameters extracted from toothpaste and saliva datasheets, supplemented by laboratory measurements, to enhance simulation accuracy. Experimental assessments encompassing the behavior of covarine particles were conducted using an optical profilometer. Viscosity tests and electrical impedance spectroscopy employing recently developed all-carbon electrodes were employed to analyze different toothpaste dilutions. The integration of experimental data from microfluidic chips with computational simulations offers thorough insights into the interactions of covarine particles with saliva and the formation of microfilms on enamel surfaces.

High solid loading, low viscosity stereolithography 3D printing ceramic cores slurry

The temperature enduring capacity of turbine blades determines the thrust-weight ratio of aero-engines. The heat dissipation efficiency of blades is improved mainly through designing complex internal cooling channel. As a transitional component of blade preparation, the shape of ceramic cores has become gradually complex. The traditional process is difficult to meet the preparation requirements of ceramic core with complex structure due to the limitation of mold. Stereolithography 3D printing provides a feasible technology for the preparation of ceramic cores with complex structures. The key to high-performance ceramic core via the stereolithography 3D printing lies in the prepare ceramic slurry with high solid loading, low viscosity and uniform stability. Choosing suitable dispersant is an effective way to prepare above standard slurry. In this study, the effects of single and dual dispersants on the rheological properties of ceramic slurry were systematically investigated. The action mechanism of the dispersant was analyzed. The functional relationship between solid loading and viscosity was elucidated. The silicon-based ceramic core slurry with 70 vol% solid loading and viscosity of 10520 mPa s (12.6 s−1) was obtained. Through optimizing printing parameters, the complex structure silicon-based ceramic core was fabricated. The influence of solid loading on the microstructure and physical properties of the ceramic core was investigated. The results show that with the increase of solid loading, the shrinkage of ceramic core lowers and the flexural strength of ceramic core strengthens. The successfully preparation of complex structure ceramic core based on high solid loading slurry promotes the extensively implemented of stereolithography 3D printing technology in the field of ceramic core.

Improving the accuracy of stereolithography 3D printed Al2O3 microcomponents by adding photoabsorber: Fundamentals and experiments

Ceramic microcomponents have a wide range of applications in microfluidic, sensors, etc. Stereolithography 3D printing technology provided a shortcut for the preparation of this small-size and complex component. With the development of device miniaturization, the existing stereolithography forms cannot meet the demand. To prepare smaller components, it is necessary to decrease the slice thickness (Cs). But during the stereolithography 3D printing, ceramic is usually easy to over-cure, leading to the key issue in the stereolithography of ceramic microcomponents: the mismatching between the curing thickness (Cp) and the slice thickness (Cs). To solve the problem above, this paper started from the stereolithography mechanism of the ceramic/resin slurry and adjusted the matching relationship between Cp and Cs theoretically by adding a photoabsorber. Then, from the experiments, the influence of different content of photoabsorber (carbon black) on curing thickness, printing accuracy, and sintering accuracy, were studied. Al2O3 ceramic microcomponents that met the design requirements were thus prepared. These results would help in the development of stereolithography 3D printing of ceramic microcomponents.

Experimental investigations into nonlinear dynamic behaviours of triply periodical minimal surface structures

Natural frequency, damping ratio and dynamic stiffness are fundamental to the performance of structures subjected to dynamic loads. Triply Periodic Minimal Surface (TPMS) composite structures, celebrated for their superior energy absorption capacity and specific strength, represent some of the most promising meta-structures. However, their dynamic properties are yet to be fully understood, thereby hindering their practical applications within civil engineering domains. Damping properties, crucial to vibration reduction, remain particularly elusive; previous studies have not successfully established a connection between these properties and the force excitation amplitude in TPMS structures. This study aims to compare the damping properties of different TPMS structures and to investigate their potential for adoption within civil engineering fields. Three types of TPMSs, including Schoen I-graph-wrapped package surface (IWP), Schwarz primitive (Primitive) and Schoen Gyroid (Gyroid), have been adopted to design solid and sheetal TPMS composite structures with identical relative density (50%) to compare their damping properties under varying excitation amplitudes. These TPMS structures are manufactured from photosensitive resin (UV resin) using stereolithography 3D printing technology. Owing to the lack of previous research into the damping properties and dynamic stiffness of TPMS structures as support structures, we have conducted single-freedom modal tests to determine the modal parameters, including natural frequency and damping ratios. Our novel results indicate that the natural frequency and damping ratio of the TPMS structures vary with the excitation amplitude. Additionally, the dynamic stiffness of TPMS structures reveals a similar decreasing trend to frequency when load amplitude escalates. As the excitation amplitude increases, the TPMS structures demonstrate softening and are capable of offering a higher vibration damping coefficient. Notably, the SS-Gyroid structure exhibits higher stiffness and damping ratio compared to other TPMS structures. These fresh insights pave the way for the integration of 3D printed smart TPMS structures within civil engineering, particularly for vibration reduction and efficient material usage. A judicious TPMS structure design can provide relatively high stiffness and damping ratio without excessive material use.

Fabrication of porous aluminum ceramics beyond device resolution via stereolithography 3D printing

This paper presents a new method for fabricating high-resolution porous ceramics using the 3D printing technology. Stereolithography 3D printing was used to create porous alumina parts with polyamide 12 (PA12) powder, alumina ceramic particles, and acrylic resin as the sacrificial porogen, aggregate, and mixture, respectively. After subsequent de-binding and sol impregnation treatments, a porous alumina part with a particle size of 15 μm was obtained after sintering. The use of aluminum sol enhanced the mechanical properties of porous alumina ceramics, thus enhancing their strength. A discrete element method model was used to simulate and explain the results, thereby providing insights into the optimization of the method design. Accordingly, this study demonstrated the potential for using the stereolithography 3D printing technology to fabricate high-resolution porous ceramics with tailored properties for various applications.

Validation of three-dimensional printed models of intracranial aneurysms.

Three-dimensional (3D) printing has evolved for medical applications as it can produce customized 3D models of devices and implants that can improve patient care. In this study, we aimed to validate the geometrical accuracy of the 3D models of intracranial aneurysms printed using Stereolithography 3D printing technology. To compare the unruptured intracranial aneurysm mesh between the five patients and 3D printed models, we opened the DICOM files in the Sim&Size® simulation software, selected the region of interest, and performed the threshold check. We juxtaposed the 3D reconstructions and manually rotated the images to get the same orientation when needed and measured deviations at different nodes of the patient and 3D printed model meshes. In the first patient, 80% of the nodes were separated by <0.56 mm and 0.17 mm. In the second patient, the deviations were below 0.17 mm for 80% of the meshes' nodes. In the next three patients, the deviations were below 0.21, 0.23, and 0.11 mm for 80% of the meshes' nodes. Finally, the overall deviation was below 0.21 mm for 80% of the mesh nodes of the five aneurysms. 3D printed models of intracranial aneurysms are accurate, having surfaces that resemble that of patients' angiographies with an 80% cumulative deviation below 0.21 mm.

Characterization of a 3D Printed Self-Powered Micropump Mould for Microfluidics Application

The number of words should not exceed 350 Self-powered infusion micropump is a non-mechanical micropumps for microfluidics application. A three- dimensional (3D) printing is an intelligent additive manufacturing technique that permits cheap, fast and accurate geometrically complex designs. In this study, a self-powered infusion micropump master mould was fabricated using stereolithography (SLA) 3D printing technique and was characterized accordingly. Furthermore, polydimethylsiloxane (PDMS) self-powered micropump from the 3D printed mould was successfully replicated using soft lithography technique. Optical microscope with i-Solution Lite imaging software was used for micropump mould dimensions characterization. It was found was that the smallest average percentage difference of 4.26 % was measured for straight inlet channel’s width between the actual mould and the computer-aided design (CAD). The average coefficient of variance (CV) for all micropump components dimensions was 3.22. It was found that the SLA 3D printing reduced manufacturing time and costs by 30.43 % and 82.84 % respectively in comparison to the standard SU-8 mould. In conclusion, SLA 3D printing technology is a viable alternative to master mould fabrication in self-infusion micropump production since it accurately reproduced the design from the CAD input.

Microstructures and mechanical properties of biphasic calcium phosphate bioceramics fabricated by SLA 3D printing

Porous biphasic calcium phosphate (BCP) bioceramics are considered to be the most promising bone repair materials in clinical medicine. Stereolithography (SLA) 3D printing can precisely fabricate bioceramic scaffolds with complex porous structure. During this process, how to obtain a suitable sintering procedure for BCP bioceramics by SLA 3D printing is the key to determine the microstructures and mechanical properties, but this is absent. In this present study, we prepared BCP bioceramics with superior densification and mechanical properties by SLA 3D printing, and mainly investigated the effects of sintering temperature and condition on the microstructures and mechanical properties of SLA 3D printed BCP bioceramics for the first time. At the optimized procedure of sintering temperature 1250 °C for 2 h, the 3D printed BCP bioceramics showed uniform shrinkage in all directions, and especially the mechanical properties were close to that of human cortical bone. Furthermore, complex porous BCP scaffolds with high porosity (51.49 %) and compressive strength (8.14 MPa) were successfully obtained. BCP bioceramics greatly promoted the proliferation of MC3T3-E1 cells by the release of Ca and P ion and presented excellent bioactivity. This work proves that SLA 3D printing technology can prepare BCP bioceramics with high mechanical and functional properties, and provides a new route for manufacturing high performance BCP bioceramic scaffolds with complex structure by SLA 3D printing for repairing bone defect in clinical.

A new and simple way to prepare monolithic solid oxide fuel cell stack by stereolithography 3D printing technology using 8 mol% yttria stabilized zirconia photocurable slurry

Yttria (8 mol%) stabilized zirconia (8YSZ) photocurable slurry is the basis for stereolithography-based 3D (SLA) printed structured electrolyte support for monolithic solid oxide fuel cell (SOFC) stack. The curing resin with trifunctional trimethylolpropane triacrylate and 1,6-hexanediol diacrylate (TMPTA/HDDA) mass ratio of 1.5:8.5 and 1 wt% of photoinitiator provided excellent curing performance and low viscosity of 2.1 mPa·s. Stable 8YSZ photocurable slurry possessing high solid content of 43 vol% and low viscosity of 3.6 Pa·s at 30 s−1 shear rate were obtained, without particle sedimentation after 180-day stability test. The activation energy of 8YSZ fabricated by 3D printing method was 0.87 eV, similar to that by dry-pressing method. The 3D printed monolithic 3-tube SOFC stack exhibited a peak power density of 230 mW·cm−2 at 850 °C. This research proves the great potential of 3D printing technology to prepare monolithic SOFC stack, paving the way to develop SOFCs for practical applications.

Ceramic paste for space stereolithography 3D printing technology in microgravity environment

Additive manufacturing techniques have demonstrated great potential in space manufacturing for long-duration human spaceflight and colonization on alien planets. Herein, we present the design and manufacturing of previously inaccessible complex ceramic components with high precision in a microgravity environment. The proposed approach is based on controlling the rheological properties of ceramic slurry in reduced-gravity. Briefly, HE-cellulose and carbomer 940 are added as thickening agents to transform the ceramic slurry into a ceramic paste(soft matter), which exhibits Bingham pseudoplastic behavior and is not sensitive to gravity variations during parabolic flight. Additionally, X-ray computed tomography (XCT) results reveal that the as-prepared alumina samples, 3D printed in a microgravity environment, render a higher density of 99.3% after sintering. The proposed route can be applied to fabricate complex-shaped ceramic components in space, enabling various possibilities of manufacturing structural and functional materials, including gradient materials, solid fuel cells, active insulation ceramic structures and piezoelectric sensors.

Stereolithography 3D printed implants: A preliminary investigation as potential local drug delivery systems to the ear

The current study is a preliminary investigation on the use of stereolithography 3D printing technology in the field of personalized medicines and specifically for delivering drugs locally, which can for example usefully be applied to ear infections. The main aim is the development of drug-loaded implants for the treatment of ear diseases, to improve patient compliance and to overcome the limitations of current delivery approaches. Multiple prototypes of implant geometries have been created and printed using a flexible resin containing 0.5% w/v of Levofloxacin. Physicochemical characterization of the printed implants was carried out using a variety of techniques (e.g., microscopic, spectroscopic, and mechanical analysis). Finally, preliminary in vitro tests were performed to evaluate the release profile of Levofloxacin, the prototype implant's stability, and their antimicrobial property. The results obtained show that there is no interaction between the resin and the drug, which is perfectly solubilized in the device. In addition, the results of the mechanical tests show that the material used resists compression without compromising the design itself, and the diffusion test has shown that the drug diffused through the matrix prototype at 50% over 3 weeks. The selected designs showed higher antimicrobial activity on E. coli than on S. aureus.

Rapid manufacturing of silica glass parts with complex structures through stereolithography and pressureless spark plasma sintering

This paper reports a method for preparing silica glass by pressureless spark plasma sintering (PL-SPS), which can rapidly manufacture silica glass parts with complex structures by coupling with stereolithography 3D printing technology. The rapid sintering process and microstructure evolution of silica glass prepared by PL-SPS were mainly investigated. The experimental results showed that the sintering temperature and dwelling time were the main factors affecting the PL-SPS of silica glass. The microstructure evolution indicated that the densification rate of the sample was very fast from 1250 °C to 1300 °C, and the interlayer defects caused by the printed layer thickness could be healed in the final stage of densification. Like conventional pressureless sintering, silica glass with a relative density of more than 99% and a visible-light transmittance of more than 90% could also be obtained through PL-SPS, but the entire working time was shortened from 22.53 h to 0.49 h.

Preparation of Mn–Zn ferrite ceramic using stereolithography 3D printing technology

In this work, tailored Mn–Zn ferrite ceramics are prepared by stereolithography (SLA) 3D printing technology, and its performances are measured utilizing the printing accuracy, magnetic properties, density, and microstructures. The major obstacle forming difficultly by single curing of self-made ferrite pastes with increasing solid content in the printing process is removed by using six scanning numbers. In addition, the prediction formulas of the linewidth and curing depth are established. The printing process parameters, namely scanning space, scanning speed, and laser power, are optimized at 2 μm, 2500 mm/s, and 240 mW, respectively. The size of convex platform bigger than 1 mm × 1.2 mm possessing circular and square holes with a diameter and a side length of 0.2 mm can be printed using the printing process parameters above. Specifically, the sintering temperature and holding time below 1200 °C and 90 min, respectively, are optimized conducive limits. The sintered parts show a density of 4.04 g/cm3 and a saturation magnetization of 58.6 emu/g, along with a small value of coercivity and remanence. The SLA-3D printing, debinding, and sintering technologies can print the complex shapes Mn–Zn ferrite ceramics using the proposed process.

Fused silica ceramic core based on network-structured zircon design via 3D printing

A ceramic core of network-structured ZrSiO4 surrounding large particles of fused quartz was designed. Experimental results show that the ceramic core prepared by digital light processing (DLP)-3D printing technology, nano-sized ZrO2 reacting with large SiO2 particles to generate network-structure ZrSiO4 in the process of re-sintering. The network structure significantly improves the bending strength of the core while maintaining a high porosity. The stable Al2O3 in the core improved the high-temperature strength of the ceramic core. This is the first study on designing the microstructure of ceramic cores using stereolithography 3D printing technology. The study provides a new idea on the additive manufacturing of ceramic cores.

549 Use of 3D Printing Technology in Surgical Planning and Decision Making in ENT Skull Base Surgery- An Axial 3D First in Northern Ireland

Abstract 39-year-old male seen at ENT clinic with inverted papilloma polyp of nasal sinus. CT showed multi-sinus mucosal thickening. The surgical options discussed were modified Lothrops endoscopic sinus surgery or an open approach of frontal sinuses with osteoplastic flap and septorhinoplasty. A model 3D skull was created by Axial 3D using stereolithography 3D printing technology with photopolymer resin. The skull was made in 1:1 scale with tolerance of 0.2mm. The tumour was printed in a contrasting colour, which allowed clear visualisation and appreciation of tumour boarders and relations to surrounding structures. The patient underwent FESS with modified Lothrops approach, achieving good clearance of polyp. The operation resulted in relief the patient’s symptoms. Discussion The use of a 3D model allowed for visualisation of tumour size and relation to surrounding anatomy, particularly the absence of dural involvement within the fontal sinus. It assisted in surgical planning. The use of the 3D skull was beneficial for patient as it allowed less invasive surgery and therefore shorter recovery time. It was also beneficial for the hospital organisation as it lowered resource requirements of theatre time, hospital bed days and staff resources. One limitation of the 3D printed skull was that the fine lamellae ethmoid air cells were not shown due to the manufacturing process. Conclusions The use of 3D printing is becoming increasingly popular as a surgical aid. We found the use of the 3D skull to be useful in individualised surgical planning for endoscopic sinus surgery.