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Three-dimensional (3D) printing is gaining significant attention as an innovative manufacturing method in various industries. In particular, 3D printed parts produced using digital light processing (DLP) have attracted considerable interest because of their rapid production and high precision. However, during the manufacturing process, the manufactured parts can experience deformation owing to accumulated residual stress and uncured resin. We analyzed part deformation during additive manufacturing and post-processing through experiments. Based on the analysis results, we propose the introduction of a sub-build plate to achieve effective manufacturing and post-processing. The sub-build plate constrains the parts, thereby enabling post-processing such as cleaning, drying, and UV post-curing to be performed more efficiently. The experimental results show that the suppression of additional deformation during UV post-curing in the parts constrained on the sub-build plate resulted in approximately a 2 % deformation. This is more than a two-fold reduction compared with the average deformation of 5.79 % observed in parts manufactured using conventional methods. These results demonstrate that the adoption of a sub-build plate can minimize part deformation, extend part lifespan, and reduce costs. These findings hold promise for the application of DLP printing technology in various industries and contribute to the development of new manufacturing processes.

Graphical abstract:

Inner ear organoids (IEOs) are 3D structures grown in vitro, which can mimic the complex cellular structure and function of the inner ear. IEOs are potential solutions to problems related to inner ear development, disease modeling, and drug delivery. However, current approaches in generating IEOs using chemical factors have a few limitations, resulting in unpredictable outcomes. In this study, we propose the use of nanomaterial-based approaches, specifically by using graphene oxide (GO). GO’s unique properties promote cell–extracellular matrix interactions and cell–cell gap junctions, thereby enhancing hair cell formation, which is an essential part of IEO development. We also investigated the potential applications for drug testing. Our findings suggest that GO is a promising candidate for enhancing the functionality of IEOs and advancing our understanding of the problems underlying inner ear development. The use of nanomaterial-based approaches may provide a more reliable and effective method for building better IEOs in the future.

Three‐ dimensional (3D) technology has been suggested to overcome several limitations in guided bone regeneration (GBR) procedures because 3D‐printed scaffolds can be easily molded to patient‐specific bone defect site. This study aimed to investigate the effect of 3‐D printed polylactic acid (PLA) scaffolds with or without hyaluronic acid (HA) in a rabbit calvaria model. A calvaria defect with a diameter of 15 mm was created in 30 New Zealand white rabbits. The rabbits were randomly allocated into three groups including no graft group (control, n= 10), 3D printed PLA graft group (3D‐PLA, n= 10), and 3D printed PLA with hyaluronic acid graft group (3D‐PLA/HA, n= 10). Five animals in each group were sacrificed at 4 and 12 weeks after surgery. Microcomputed tomography and histologic and histomorphometric analyses were performed. Over the whole examination period, no significant adverse reactions were observed. There were no statistically significant differences in bone volume (BV) /tissue volume (TV) among the three groups at 4 weeks. However, the highest BV/TV was observed in the 3D‐PLA/HA group at 12 weeks. The new bone area for control, 3D‐PLA, and 3D‐PLA/HA showed no statistical differences at 4 weeks. However, the value was significantly higher in the 3D‐PLA and 3D‐PLA/HA groups compared to the control group at 12 weeks. The 3D printed PLA scaffolds was biocompatible and integrated well with bone defect margin. They were also provided the proper space for new bone formation. Therefore, 3D printed PLA/HA might be a potential tool to enhance bone augmentation.

Abstract

Two-photon lithography has emerged as a highly effective method for fabricating intricate three-dimensional (3D) microstructures. It enables the rapid fabrication of 3D microstructures, unlike conventional two-dimensional nanopatterning. Researchers have extensively investigated two-photon polymerization (TPP) for the fabrication of diverse 3D micro/nanodevices with high resolution. TPP can be applied in cell cultures, metamaterials, optical materials, electrical devices, and fluidic devices, to name a few. In this study, we investigate the applications and innovative research pertaining to TPP, which is an effective fabrication technique with significant advancement in various fields. In particular, we attempt to determine the reasons that cause the detachment or delamination of 3D microstructures during the development process and propose some solutions. A step-by-step fabrication process for a glass substrate, from photoresist deposition to laser scanning and the dissolution of the uncured photoresist, is presented. Defects such as pattern delamination are discussed, with emphasis on the cell scaffold structure and microlens array. Understanding and addressing these defects are vital to the success of 3D microstructure fabrication via TPP.

The femtosecond laser sintering of metal nanoparticles was studied in order to fabricate submicron-sized metal patterns on flexible polymer substrates for various applications in the electronic and photonic industries. In this process, a mode-locked Ti:sapphire laser beam was tightly focused on silver nanoparticles. To achieve a homogeneous dispersion of the silver nanoparticles, the nanoparticles were prepared using a two-phase reduction method wherein the silver nanoparticles were encapsulated by functional surfactants. The key advantage of the femtosecond laser sintering process is that it reduces the heat-affected zone during sintering, as the femtosecond (10–15 s) laser pulse is shorter than the heat diffusion time (picosecond: 10–12 s). Therefore, sintering of metal nanoparticles is limited to the laser focal spot and the thermal diffusion effect is suppressed, enabling the realisation of submicron-sized metal patterns on flexible polymer substrates. Through this process, metal conductors with submicron-sized features and high conductivity were successfully fabricated. As demonstrated by the obtained results, the femtosecond laser sintering of metal nanoparticles is a process that offers direct, low-temperature, ultra-high-resolution results, and which will have numerous further applications in flexible electronics.