Light Processing Technology Research Articles

Effect of Build Orientation on Mechanical and Physical Properties of Additively Manufactured Resins Using Digital Light Processing Technology in Dentistry: A Systematic Review.

The aim of this systematic review was to evaluate the effect of build orientation on the mechanical and physical properties of additively manufactured resin using digital light processing (DLP). The properties of 3D-printed materials are influenced by various factors, including the type of additive manufacturing (AM) system and build orientation. There is a scarcity of literature on the effect of build orientation on the mechanical and physical properties of additively manufactured resins using DLP technology in dentistry. This study followed the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines and was registered in PROSPERO. The formulated population, intervention, comparison, outcome (PICO) question was "What is the effect of build orientation on the mechanical and physical properties of additively manufactured resins produced using DLP in dentistry." The search strategy used three main electronic databases and an additional manual search was done until February 2024. All the studies that evaluated the correlation of build orientation and the properties of printed resin using DLP were included. Two different analysis was used for in vivo and in vitro studies to assess the risk of bias. On search 237 studies were yielded for systematic review, out of which 13 studies were included for the systematic review evaluation. On evaluation and reviewing the included studies, though the build orientation angle influenced the properties of printed resins the results obtained were varied as 90° angle had increased compressive strength, low surface roughness, and best accuracy. The 0° angle had better wear resistance, tensile strength, and high flexural strength. There was no influence of build orientation on microhardness, shear bond strength, gloss and color difference. The studies on denture base showed that 45° build angle showed the truest with best accuracy. The build orientation angle effects on both the mechanical and physical properties of the additively manufactured resin but varies with each property. The build orientation can be chosen based on the type of properties to be achieved based on the treatment modality. Based on the systematic review results the specific build orientation angle should be used during fabrication of any denture designs, crowns, and bridges as it is correlated with the properties to be achieved by particular designs. How to cite this article: Paranna S, Thosar N, Kanitkar A. Effect of Build Orientation on Mechanical and Physical Properties of Additively Manufactured Resins Using Digital Light Processing Technology in Dentistry: A Systematic Review. J Contemp Dent Pract 2024;25(9):891-903.

Improved mechanical performance and forming accuracy of ZrO2 fixed partial denture based on the digital light processing technology

Fixed partial dentures are the primary treatment for dentition defects. Digital light processing (DLP) 3D printing technology is an advanced technique with significant advantages and potential in the field of dental restoration, particularly in cases requiring high precision and personalization. However, challenges persist in printing fixed partial dentures that meet the strength requirements for clinical applications. In this study, we aimed to optimize printing parameters, including exposure time and layer thickness, to enhance dimensional accuracy, reduce warpage, and improve the surface quality of the samples. Additionally, we focused on the rheological and curing properties of the paste. The optimal combination of printing parameters was found to be 5 s of exposure time and 50 μm layer thickness, achieving superior dimensional accuracy, reduced warpage, and improved surface quality. For a slurry with 40% solid content, the dispersant KOS 110 demonstrated the best shear thinning effect, with an optimal addition of 2%. Notably, the Vickers hardness, flexural strength, and fracture toughness of the ZrO2 fixed partial dentures were 13.52 ± 0.21 GPa, 940 ± 20 MPa, and 6.92 ± 0.25 MPa·m1/2, respectively, which surpasses that of human enamel (4 GPa) and is comparable to CAD/CAM ZrO2 (900–1200 MPa). This study demonstrates that DLP technology can be effectively used to fabricate ZrO2 personalized complex fixed partial dentures with excellent mechanical properties and high precision, offering broad application prospects in stomatology.

Study of the High-Temperature Sintering Characteristics of Boron Oxide Composite Silicon-Based Ceramics

This paper explores the application of boron oxide (B2O3) as a sintering additive in silicon-based (SiO2) ceramics, focusing on its impact on the sintering process and resulting ceramic properties. Composite silicon-based ceramic shells with boron oxide content ranging from 0 to 4 Wt% were prepared using digital light processing (DLP) technology. This study examines the effects of boron oxide on sintering temperature, apparent porosity, shrinkage rates, and mechanical properties during high-temperature sintering. Experimental results indicate that, as boron oxide content increases, the shrinkage rate of the ceramic samples rises progressively, with shrinkage in the XY direction increasing from 4.57% to 16.40% and in the Z direction from 6.25% to 17.03%. Concurrently, the apparent porosity decreases with higher boron oxide content, ranging from a maximum of 36.17% to a minimum of 23.27%. Bulk density also improves from 1.49 g/cm3 to 1.78 g/cm3. The bending strength trend first rises and then declines, peaking at 15.39 MPa at a boron oxide content of 3 Wt%. X-ray Diffraction and Energy Dispersive Spectroscopy analyses confirm that the addition of boron oxide promotes the formation of beta-quartz and that its liquid-phase behavior at high temperatures aids in enhancing ceramic densification. This study demonstrates that an appropriate amount of boron oxide can effectively lower the sintering temperature of silicon-based ceramics while improving their mechanical properties, providing a theoretical foundation and practical basis for broader industrial applications.

Development of a Multiplex Colorimetric Genetic Analysis Microchip for Identifying Foodborne Pathogens Using 3D-Printer

The rapid and accurate detection of foodborne pathogens is paramount for safeguarding public health and ensuring the safety of food supplies. In this study, we introduce a groundbreaking approach in the form of a 3D printed multiplex colorimetric genetic analysis microchip tailored specifically for point-of-care analysis of foodborne pathogens. This microchip represents a significant advancement in genetic analysis technology, offering a streamlined and efficient solution for on-site detection.Conventional methods for fabricating genetic analysis chips often involve photolithography, which can be time-consuming, expensive, and technically demanding. In contrast, our microchip is fabricated using stereolithography-digital light processing (SL-DLP) technology, which offers several distinct advantages. SL-DLP is known for its convenience, reproducibility, and cost-effectiveness, making it an ideal choice for the rapid and scalable production of genetic analysis chips. By leveraging this innovative fabrication technique, we have overcome many of the limitations associated with traditional manufacturing methods, paving the way for enhanced accessibility and widespread adoption of genetic analysis technologies.The genetic analysis microchip consists of several key components, each meticulously designed to facilitate efficient and accurate detection of foodborne pathogens. Central to its functionality is the inclusion of a cell sample solution inlet, which allows for the introduction of the sample into the microchip. This inlet is strategically positioned to ensure uniform distribution of the sample throughout the microchip, maximizing the efficiency of the detection process. Additionally, the microchip features four reaction chambers, each dedicated to the isothermal amplification of a different target pathogen. This multiplexing capability enables simultaneous detection of multiple pathogens, greatly enhancing the efficiency and throughput of the analysis process.To further streamline the detection process, the microchip incorporates four loop-mediated isothermal reaction (LAMP) reagent inlets, allowing for the pre-loading of lyophilized reagents into each reaction chamber. This pre-loading step eliminates the need for manual addition of reagents, reducing the risk of contamination and human error. Furthermore, the microchip is fabricated using a photocurable resin composed of poly(ethylene glycol) diacrylate (PEG-DA) (MW=258), which offers several advantages. Notably, this resin enables the printing of high-resolution and transparent structures, facilitating clear observation of color changes indicative of successful gene amplification.To enable colorimetric genetic analysis, Eriochrome Black T (EBT) is added to the LAMP reagent, inducing a distinctive color change upon amplification of the target gene. This colorimetric signal serves as a visual indicator of pathogen presence, allowing for rapid and intuitive interpretation of results. In our experiments, we successfully detected four common foodborne pathogens - Escherichia coli O157:H7, Salmonella enterica, Vibrio parahaemolyticus, and Listeria monocytogenes - within a remarkably short timeframe of 20 minutes. This rapid turnaround time is critical for timely intervention and mitigation of foodborne illness outbreaks.To assess the sensitivity of our microchip, we conducted a limit of detection (LOD) test using samples containing varying concentrations of the target pathogen. Remarkably, we were able to detect as few as 10 cells of the pathogen with a high degree of accuracy, underscoring the sensitivity and reliability of our approach. Furthermore, in multiplex detection tests, each target gene was independently detected within dedicated LAMP chambers, demonstrating the microchip's exceptional specificity and its ability to accurately distinguish between different pathogens.Importantly, the simplicity of fabrication and the readiness for on-site analysis make our microchip highly versatile and adaptable to a wide range of applications beyond food safety. In addition to foodborne pathogen detection, our microchip holds promise for use in clinical diagnosis, forensic analysis, and environmental monitoring. By enabling rapid and accurate genetic analysis in diverse settings, our microchip has the potential to revolutionize the field of molecular diagnostics and significantly improve public health outcomes.In summary, we have developed a novel 3D printed multiplex colorimetric genetic analysis microchip that represents a significant advancement in point-of-care diagnostic technology. By combining state-of-the-art fabrication techniques with innovative design principles, we have created a powerful tool for the rapid and reliable detection of foodborne pathogens. Moving forward, we envision widespread adoption of our microchip as a cornerstone of food safety protocols, facilitating proactive measures to protect consumer health and prevent foodborne illness outbreaks.

Extraction of type I collagen and development of collagen methacryloyl (ColMA)/PEGDA ink for digital light processing printing

The fabrication of three-dimensional (3D) biostructures through additive manufacturing relies on the critical role of ink development. With the growing demand for high-resolution manufacturing, digital light processing (DLP) technology has emerged as a promising technique requiring specialised photosensitive inks. Although gelatine methacryloyl (GelMA) has been the primary option for DLP, its mechanical properties, biocompatibility, and low stability still present limitations. The development of collagen-based ink is thus in high demand for a wider stiffness adjustment range, native bioactivities, and versatility in biomedical engineering applications. In this paper, we report a rapid and low-cost protocol for collagen methacryloyl (ColMA)/poly(ethylene glycol) diacrylate (PEGDA) ink for DLP printing. The ink demonstrated the highest printing resolution of ∼50 μm by using 405 nm visible light. The printability, mechanical properties and cell viability of the DLP-printed ColMA/PEGDA structures were comprehensively evaluated. The printed ColMA/PEGDA structures reached a compressive modulus over 100 kPa with 0.6 wt% collagen. The printed ColMA/PEGDA scaffolds promoted the attachment and proliferation of 3 T3 fibroblasts, demonstrating their potential in future applications in biomedical engineering.

A Scalable Digital Light Processing 3D Printing Method.

The 3D printing method based on digital light processing (DLP) technology can transform liquid resin materials into complex 3D models. However, due to the limitations of digital micromirror device (DMD) specifications, the normal DLP 3D printing method (NDPM) cannot simultaneously process large-size and small-feature parts. Therefore, a scalable DLP 3D printing method (SDPM) was proposed. Different printing resolutions for a part were designed by changing the distance between the projector and the molding liquid level. A scalable DLP printer was built to realize the printing resolution requirements at different sizes. A series of experiments were performed. Firstly, the orthogonal experimental method was used, and the minimum and maximum projection distances were obtained as 20.5 cm and 30.5 cm, respectively. Accordingly, the layer thickness, exposure time, and waiting leveling time were 0.08 mm, 3 s, and 6 s and 0.08 mm, 7 s, and 10 s. Secondly, single-layer column feature printing was finished, which was shown to have two minimum printing resolutions of 101 μm and 157 μm at a projection distance of 20.5 cm and 30.5 cm. Thirdly, a shape accuracy test was conducted by using the SDPM. Compared with the NDPM, the shape accuracy of the small-feature round, diamond, and square parts was improved by 49%, 42%, and 2%, respectively. This study verified that the SDPM can build models with features demonstrating high local shape accuracy.

Effect of ZrSiO4 as additive on the mechanical properties of DLP printing porous mullite ceramics

In order to satisfy the demand for mullite porous ceramics with complex geometries in the engineering field, the digital light processing (DLP) technology is employed to prepare mullite porous ceramics in this study. However, the poor mechanical properties of the mullite porous ceramics prepared using the DLP technology limits its further application in engineering field. In this work, the microstructure of mullite crystals was regulated by adding the sintering aid ZrSiO4 to enhance the mechanical properties of the mullite ceramics, and the effects of sintering aid ZrSiO4 content and sintering temperature on the internal microstructure evolutions of mullite porous ceramics were investigated. Results showed that the decomposition of ZrSiO4 promoted the generation of the silica-rich liquid phase at high temperatures, which effectively promoted the nucleation and growth of needle-like mullite crystals. When the sintering temperature was 1600 °C and the ZrSiO4 content was 10 wt%, the well-developed elongated crystals formed an interlocking nonwoven structure. The corresponding mullite porous ceramics exhibited a compressive strength of 2.52 MPa and a porosity of 74.51 %. The strategy of this study can be a feasible route for preparing lightweight and high-strength mullite porous ceramics via digital light processing.

Zirconia crowns manufactured using digital light processing: Effects of build angle and layer thickness on the accuracy

ObjectivesThis study investigated the effects of build angle and layer thickness on the trueness and precision of zirconia crowns manufactured using digital light processing (DLP) technology. Materials and MethodsSingle crowns were fabricated from zirconia using DLP technology. The crowns were manufactured with three different representative build angles (0°, 45°, and 90°) and two different layer thicknesses (30 μm and 50 μm). After printing, the specimens were non-contact-scanned, and their accuracy was assessed using a 3D analysis software. Root mean square (RMS) values were used to determine trueness and precision. Color maps were generated to detect deviations within the specimens. Statistical analyses were conducted using two-way ANOVA. ResultsBuild angle and layer thickness significantly affected trueness and precision (p < 0.05). At a 30-μm layer thickness, the crowns printed at angles of 0° (32.2 ± 3.2 μm) and 45° (33.9 ± 2.4 μm) demonstrated the best marginal trueness compared to those in other groups (p < 0.05). Notably, those printed at an angle of 90° exhibited the best intaglio surface trueness (37.4 ± 4.0 μm). At a 50-μm layer thickness, the crowns printed at an angle of 90° exhibited the lowest accuracy concerning marginal and intaglio surface aspects (27.7 ± 8.2 μm). ConclusionsBoth the build angle and layer thickness significantly affected the dimensional accuracy of DLP-printed zirconia crowns, with the 30-μm layer thickness offering superior trueness. Optimal results were achieved using build angles of 0° and 45° in conjunction with thinner layers, minimizing marginal defects. Clinical SignificanceAll zirconia crowns produced at different build angles and layer thicknesses satisfied clinical requirements. Specific combinations of these factors realized the fabrication of single crowns that possessed the highest accuracy.

Numerical and experimental investigation of 3D printed tunable stiffness metamaterial with real-time response using digital light processing technology

A tunable mechanical metamaterial is a type that can be altered or manipulated to change its physical properties in various situations. This study introduces a novel type of metamaterial, hydro-tunable metamaterials (HTMs), which can be dynamically adjusted in real-time by filling or draining it with water. The development of HTMs has significant implications for various fields, including mechanical engineering, biomedical applications, and energy absorption. The study involves designing and manufacturing HTMs using a Digital Light Processing (DLP) 3D printing process. The design process involves modifying an initial basic auxetic structure to create a closed and sealed structure accommodating fluid. The printed samples are then characterized using mechanical testing and finite element analysis (FEA). Experiments and simulations have found that a sample containing water behaves differently from a sample without water, resulting in an increase in stiffness. This difference can be leveraged to modify the stiffness and strength of the structure. This phenomenon is attributed to the incompressibility of water within the structure. Water exerts a hydrostatic pressure on the auxetic material, resulting in increased stiffness and resistance to compression. This technique highlights the potential of HTMs to be dynamically adjusted in real-time, leading to enhanced energy absorption and improved performance. An additional FEA was conducted to examine the impact of water pressure on the mechanical behavior of the structure. The results indicate that applying pressure or temperature to the water can significantly enhance the mechanical properties of the water-filled sample.

Microstructural evolution, enhanced mechanical properties, and complex shapes design in high solid content alumina ceramics through additive manufacturing

Manufacturing industrially profitable high solid-loading ceramic materials with finely designed complex shapes is an exciting yet challenging in sustainable additive manufacturing. Here, we propose a resin strategy to achieve a high solid-loading content of 62 vol% alumina slurry for 3D printing high-quality complex shapes using digital light processing (DLP) technology. Remarkably, both high solid-loading content and tuned sintering temperature emerge as key factors in ensuring optimal print quality and mechanical performance. With this strategy, the ceramic slurry containing 62 vol% exhibits lower shear rate and improved layer adhesion. The burnout treatment was designed based on the DSC-TGA results, followed by sintering in an air atmosphere. Comprehensive physical measurements were achieved, alongside precise structural characterization at multilength scales in situ. In depth exploration of post-sintering analysis revealed no changes in phase composition or chemical bonding. The optimum overall performance of sintered specimen exhibited shrinkage of 8.3 %, 8.8 %, and 11.5 % in the X, Y, and Z directions, with a bulk density of 3.76 g/cm3. Mechanical testing demonstrated superior flexural strength of 247.23 MPa, nanoindentation hardness of 30.9 GPa, and modulus of 428.35 GPa. This high-precision printing strategy may significantly contribute to understanding the structure-property relationship of DLP-3D printed Al2O3 ceramic and opening avenue for the applications of high-strength parts in demanding environments.

Photocurable Foam for Three-Dimensional-Printed Porous Structures.

In this research, a foam three-dimensional (3D) printing method using digital light processing (DLP) technology was developed to fabricate 3D-printed porous structures. To address the challenges in preparing DLP precursor foam fluid, we designed a specialized foaming device. This device enables the precursor solution to be blended with air, resulting in a stable foam precursor with an adjustable air/liquid fraction and suitable fluidity, crucially enhancing the gas-liquid contact time for the printing process. By manipulation of fluid flow rates, cycle counts, and gas/liquid ratios, one can easily prepare uniform foams with precise control over the pore size and porosity. To avoid significant volume reduction during ultraviolet (UV) curing, nanoparticle fillers were introduced into the network to prevent collapse of the foam structure. Furthermore, the inclusion of an UV absorber enhanced the quality of the printing process by addressing the limitations associated with particle scattering and reflection. The DLP process can readily fabricate intricate structures, featuring a planar resolution below 30 μm and a printing accuracy of less than 1%. Several examples were also demonstrated to highlight the advantages of this technology and its ability to directly print custom foam structures, thereby saving time and material resources.

Size shrinkage and compressive behaviour of Al2O3 honeycomb structures fabricated via Digital Light Processing technology

Al2O3 ceramic have excellent chemical inertness, superior heat resistance, and excellent corrosion resistance, so they are considered ideal materials for manufacturing high-performance components such as thermal end devices in aerospace, heat dissipation panels in electronic communication, and exhaust filters in the automotive industry. Digital Light Processing (DLP) is a useful technology to fabricate complex Al2O3 ceramic components. However, the size shrinkage effect of DLP-fabricated components need to be investigated deeply before its further application. In this work, we utilized DLP technology to fabricate Al2O3 ceramic honeycomb structures and systematically investigated their microstructure, size shrinkage, and mechanical properties. Our findings revealed that the Al2O3 ceramic grains exhibit flake-like structures with an average diameter of 1–2 μm, and the ceramic particles are tightly bonded. The shrinkage rates in the X and Y axes were 7.54 % and 7.42 %, respectively, while the Z-axis exhibited a more significant shrinkage of 13.04 %. This anisotropic shrinkage in different direction was attributed to accumulation of the interlayer bonding under gravity action during debinding and sintering process. The compressive stress-strain curve of the honeycomb structures demonstrated a typical brittle compressive behavior, including elastic, stress plateau, and brittle fracture stages. The honeycomb structures exhibited an elastic modulus of 54.49 ± 1.22 MPa and a compressive strength of 10.22 ± 0.42 MPa. The fracture analysis indicated that the fractures region of honeycomb structures initiated at the corners of the honeycomb structures, indicating their easy-broken compared to the walls. These findings provide valuable guidance for the high-precision and high-performance manufacturing of complex Al2O3 ceramic components.

Indoor space thermal cycle design and animation 3D modeling based on digital light processing technology

With the continuous development of architectural design concepts, the thermal cycle optimization of interior space has become an important topic to improve energy efficiency and comfort. The introduction of digital light processing (DLP) technology provides new possibilities for 3D modeling and thermal cycle analysis. This study uses digital light processing technology to design and optimize the thermal cycle of indoor space, and explores its application in real-time animation 3D modeling to provide a more intuitive visual display. DLP technology is used to build a three-dimensional model of interior space, and heat flow analysis software is combined to simulate the thermal cycle of different design schemes. The dynamic simulation method was used to analyze the change of heat circulation in the exhibition room and its influence on the indoor environment. The results show that the indoor thermal cycle optimized by DLP technology can effectively improve the heat distribution uniformity and energy efficiency utilization, and the simulation results show that the improved scheme has significant advantages in thermal comfort. This study proves the feasibility and effectiveness of digital light processing technology in indoor space thermal cycle design, and provides a new idea for future architectural design and thermal cycle management.

Mechanical Properties of Additive-Manufactured Composite-Based Resins for Permanent Indirect Restorations: A Scoping Review.

The introduction of 3D printing technology in dentistry has opened new treatment options. The ongoing development of different materials for these printing purposes has recently enabled the production of definitive indirect restorations via 3D printing. To identify relevant data, a systematic search was conducted in three databases, namely PubMed, Scopus, and Web of Science. Additionally, a manual search using individual search terms was performed. Only English, peer-reviewed articles that encompassed in vitro or in vivo research on the mechanical properties of 3D-printed composite materials were included, provided they met the predefined inclusion and exclusion criteria. After screening 1142 research articles, 14 primary studies were selected. The included studies mainly utilized digital light processing (DLP) technology, less commonly stereolithography (SLA), and once PolyJet printing technology. The material properties of various composite resins, such as VarseoSmile Crown Plus (VSC) and Crowntec (CT), were studied, including Vickers hardness, flexural strength, elastic modulus, compressive strength, tensile strength, fracture resistance, and wear. The studies aimed to compare the behavior of the tested additive composites to each other, conventional composites, and subtractive-manufactured materials. This scoping review examined the mechanical properties of composites used for 3D printing of definitive restorations. The aim was to provide a comprehensive overview of the current knowledge on this topic and identify any gaps for future research. The findings suggest that 3D-printed composites are not yet the first option for indirect restorations, due to their insufficient mechanical properties. Due to limited evidence, more research is needed in this area. Specifically, there is a need for clinical trials and long-term in vivo research.

Effect of ZrO2 content on mechanical properties of SiC ceramics prepared based on digital light processing

Digital light processing (DLP) technology shows promise in addressing the challenges of preparing high-strength, precise, and complex SiC ceramic structural parts. However, the low strength of DLP-printed SiC ceramic parts remains a persistent issue. To address this, a nano-ZrO2 particle enhancement strategy is proposed. This study systematically investigates the effects of ZrO2 content on slurry viscosity, curing depth, microscopic morphology, and the mechanical properties of SiC ceramics. The results indicate that increasing the ZrO2 content raises the viscosity of the SiC slurry and decreases the curing depth, which can adversely affect the printing quality of SiC ceramic green bodies. However, a higher ZrO2 content significantly reduces pore defects in the sintered parts, improving densification and mechanical properties. This underscores the importance of optimizing ZrO2 content. The SiC sintered parts reinforced with ZrO2 particles exhibited outstanding properties, including a relative density of 91.1 ± 3.2 %, Vickers hardness of 996.4 ± 93.8 HV, and a flexural strength of 201.5 ± 11.4 MPa. This study provides a straightforward and effective method for producing high-strength SiC ceramics via DLP.

Particle grading and debinding process of zirconia ceramic based on digital light process

Digital light processing technology has the advantages of high molding accuracy and the ability to prepare complex structures, which is commonly used in the preparation of resin or ceramics. By mixing two particle sizes of zirconia powders, this paper successfully prepared a 60 vol% slurry with a low viscosity of 1.28 Pa s at shear rate was 50 s−1. By systematically studying the rheological properties of the mixed slurry, the curing depth was exceeding 100 μm at exposure time of 3 s. Furthermore, by investigating the debinding process of the printed sample, it is found that the sintering sample after debinding in vacuum has the highest density. This work has a positive significance for the preparation and debinding process of high solid loading ceramic slurry.

Attapulgite‐Reinforced Robust and Ionic Conductive Composite Hydrogels for Digital Light Processing 3D Printing

AbstractIonic conductive hydrogels are widely used in many applications such as electrochemical energy storage, flexible electronic devices, and catalyst transistors due to their excellent ionic conductivity as well as chemical stability. However, the fragile mechanical properties and the lack of shaping methods severely limit their further applications. Herein, an ionic conductive composite hydrogel with reinforced mechanical properties is demonstrated that can be rapidly 3D printed using digital light processing technology. By using both γ‐methacryloxypropyltrimethoxysilane moderately modified attapulgite rigid particle and polyvinyl alcohol (PVA) semicrystal dual‐network reinforcement, the mechanically robust and highly conductive N,N,N‐trimethylethanaminium‐chloride‐based hydrogels are obtained, demonstrating a 5 times higher tensile strength than the initial one due to the turning and orienting of the attapulgite as well as the robust PVA secondary network. Furthermore, encapsulation strategy is used to avoid the dehydration of hydrogel, and strain sensors that exceed the strain limit of the hydrogel are fabricated through structural design. This work provides a reference for attapulgite‐reinforced hydrogel in biosensing.

Light‐Processed 3D Bioprinting of Symblepharon Rings Fortified with l‐Ascorbic Acid for Ocular Tissue Engineering

AbstractThis study aims to develop gelatin methacryloyl (GelMA)‐based symblepharon rings fortified with l‐ascorbic acid (lAA), aiming for controlled release of vitamins for the treatment of the ocular surface, corneal healing, and acceleration of epithelial growth, while concurrently preventing potential inflammation. The human tears contain abundant IAA, which serves a protective role for ocular tissues. The utilization of 3D printing digital light processing technology not only navigating the manufacturing process of symblepharon rings, addressing challenges related to commercial production and expedited delivery to patients but also imparts enhanced flexibility compared to commercial products. This innovative approach also facilitates the production of rings that exhibit superior softness and are amenable to mechanical movements for ocular tissue engineering. The morphological, chemical, rheological, biological, thermal, and drug‐release characteristics of 3D‐printed lAA‐loaded symblepharon rings are investigated. In the morphological characterization, it is observed that the rings exhibit a porous structure. In biocompatibility tests, Gelas and Gelas‐low rings achieve over 75% viability. Following the cell test, scanning electron microscope images reveal fibroblasts adhering to Gelas and Gelas‐low rings, spreading across their surfaces. Drug release studies conducted in phosphate‐buffered saline at pH 7.4 reveal the complete release of lAA from Gelas‐low within a 5‐d incubation period.

Three-Dimensional Bioprinted Skin Microrelief and Its Role in Skin Aging.

Skin aging is a complex physiological process, in which cells and the extracellular matrix (ECM) interreact, which leads to a change in the mechanical properties of skin, which in turn affects the cell secretion and ECM deposition. The natural skin microrelief that exists from birth has rarely been taken into account when evaluating skin aging, apart from the common knowledge that microreliefs might serve as the starting point or initialize micro-wrinkles. In fact, microrelief itself also changes with aging. Does the microrelief have other, better uses? In this paper, owing to the fast-developing 3D printing technology, skin wrinkles with microrelief of different age groups were successfully manufactured using the Digital light processing (DLP) technology. The mechanical properties of skin samples with and without microrelief were tested. It was found that microrelief has a big impact on the elastic modulus of skin samples. In order to explore the role of microrelief in skin aging, the wrinkle formation was numerically analyzed. The microrelief models of different age groups were created using the modified Voronoi algorithm for the first time, which offers fast and flexible mesh formation. We found that skin microrelief plays an important role in regulating the modulus of the epidermis, which is the dominant factor in wrinkle formation. The wrinkle length and depth were also analyzed numerically for the first time, owing to the additional dimension offered by microrelief. The results showed that wrinkles are mainly caused by the modulus change of the epidermis in the aging process, and compared with the dermis, the hypodermis is irrelevant to wrinkling. Hereby, we developed a hypothesis that microrelief makes the skin adaptive to the mechanical property changes from aging by adjusting its shape and size. The native-like skin samples with microrelief might shed a light on the mechanism of wrinkling and also help with understanding the complex physiological processes associated with human skin.

Strong and tough β-TCP/PCL composite scaffolds with gradient structure for bone tissue engineering: Development and evaluation

Bioactive ceramic bone scaffolds are limited by their brittleness. To address this limitation, we developed a new method for preparing β-tricalcium phosphate (β-TCP)/polycaprolactone (PCL) porous composite scaffolds with a gradient structure using digital light processing technology and an impregnation process. The composite scaffolds exhibited compressive strength comparable to that of pure β-TCP scaffolds but with substantially higher toughness and reliability, especially during in vitro degradation. Owing to the gradient structure, the composite scaffolds could gradually shift from high strength and stiffness to moderate strength and low stiffness, which is beneficial for bone healing and remodeling. In femoral condyle defects without mechanical stimulation, the β-TCP/PCL composite scaffolds exhibited slightly lower cellular compatibility and osteoinductive ability than those of the pure β-TCP scaffolds. However, in radial defects, composite scaffolds demonstrated a better mechanical response and bone growth capacity. The composite scaffolds maintained their structural integrity after 2–4 months, whereas the β-TCP scaffolds fractured within 2 months. This study provides a novel methodology for the development of effective scaffold fabrication strategies for load-bearing or large segmental defects with complex stress applications for use in bone healing and remodeling.