Mask image projection-based vat photopolymerization (MIP-VPP) offers advantages like low cost, high resolution, and a wide material range, making it popular in industry and education. Recently, MIP-VPP employing liquid crystal displays (LCDs) has gained traction, increasingly replacing digital micromirror devices, particularly among hobbyists and in educational settings, and is now beginning to be used in industrial environments. However, LCD-based MIP-VPP suffers from pronounced pixelated aliasing arising from LCD’s discrete image pixels and its direct-contact configuration in MIP-VPP machines, leading to rough surfaces on the 3D-printed parts. Here, we propose a vibration-assisted MIP-VPP method that utilizes a microscale vibration to uniformize the light intensity distribution of the LCD-based mask image on VPP’s building platform. By maintaining the same fabrication speed, our technique generates a smoother, non-pixelated mask image, reducing the roughness on flat surfaces and boundary segments of 3D-printed parts. Through light intensity modeling and simulation, we derived an optimal vibration pattern for LCD mask images, subsequently validated by experiments. We assessed the surface texture, boundary integrity, and dimensional accuracy of components produced using the vibration-assisted approach. The notably smoother surfaces and improved boundary roughness enhance the printing quality of MIP-VPP, enabling its promising applications in sectors like the production of 3D-printed optical devices and others.

Optical lenses require feature resolution and surface roughness that are beyond most (3D) printing methods. A new continuous projection-based vat photopolymerization process is reported that can directly shape polymer materials into optical lenses with microscale dimensional accuracy (< 14.7 µm) and nanoscale surface roughness (< 20 nm) without post-processing. The main idea is to utilize frustum layer stacking, instead of the conventional 2.5D layer stacking, to eliminate staircase aliasing. A continuous change of mask images is achieved using a zooming-focused projection system to generate the desired frustum layer stacking with controlled slant angles. The dynamic control of image size, objective and imaging distances, and light intensity involved in the zooming-focused continuous vat photopolymerization are systematically investigated. The experimental results reveal the effectiveness of the proposed process. The 3D-printed optical lenses with various designs, including parabolic lenses, fisheye lenses, and a laser beam expander, are fabricated with a surface roughness of 3.4 nm without post-processing. The dimensional accuracy and optical performance of the 3D-printed compound parabolic concentrators and fisheye lenses within a few millimeters are investiagted. These results highlight the rapid and precise nature of this novel manufacturing process, demonstrating a promising avenue for future optical component and device fabrication.

Additive manufacturing (AM) is a digital manufacturing process that can directly convert a computer‐aided design model into a physical object in a layer‐by‐layer manner. Due to the additive and discrete nature of the digital manufacturing process, AM needs to find a trade‐off between process resolution and production efficiency. Traditional AM processes balance the resolution and efficiency by tuning the processes either in the temporal domain (e.g., higher speed in serial processes) or in the spatial domain (e.g., more tools in parallel processes). To improve the resolution without sacrificing efficiency, a data‐driven mask image planning method based on subpixel shifting in a split second by tuning the process in both temporal and spatial domains is presented. The method is based on the optimized pixel blending principle and a fast error diffusion‐based optimization model. Various simulation and experimental tests are carried out to verify the developed subpixel shifting method. The experimental results demonstrate the data‐driven‐based mask image calibration and planning techniques significantly improve the fabricated part quality without compromising the process efficiency. The presented spatiotemporal strategy may shed light for future research on the projection‐based AM processes.

Microscale surface structures are commonly found on macroscale bodies of natural creatures for their unique functions. However, it is difficult to fabricate such multi-scale geometry with conventional stereolithography processes that rely on either laser or digital micromirror device (DMD). More specifically, the DMD-based mask projection method displays the image of a cross-section of the part on the resin to fabricate the entire layer efficiently; however, its display resolution is limited by the building area. In comparison, the laser-based vector scanning method builds smooth features using a focused laser beam with desired beam-width resolution; however, it has less throughput for its sequential nature. In this paper, we studied the hybrid-light-source stereolithography process that integrates both optical light sources to facilitate the fabrication of macro-objects with microscale surface structures (called micro-textures in the paper). The hardware system uses a novel calibration approach that ensures pixel-level dimensional accuracy across the two light sources. The software system enables designing the distribution and density of specific microscale textures on a macro-object by generating projection images and laser toolpaths for the two integrated light sources. Several test cases were fabricated to demonstrate the capability of the developed process. A large fabrication area (76.8 mm × 80.0 mm) with 50 μm micro-features can be achieved with a high throughput.

In article number 2003725, Xiangjia Li, Yang Chai, Yong Chen, and co-workers present limpet tooth inspired painless microneedles with the capability of controllable drug delivery. The microneedles are fabricated via a magnetic field-assisted 3D printing process, and the aligned magnetic nanoparticles show promising enhanced compression resistance. This opens intriguing perspectives for designing microneedles with sharp features and excellent mechanical strength based on bioinspired hierarchical structures.

The research of functional magnetic materials has become a hot topic in the past few years due to their fast, long-range, and precise response in diverse environments. Functional magnetic devices using different magnetic materials and structure designs have been developed and demonstrated good advantages to enable various applications. However, the required magnetic materials and structure designs for diverse functions also increase the fabrication difficulties while developing such devices. 3D printing technology presents a powerful and promising manufacturing approach to rapidly fabricate functional magnetic devices of complex geometries in multiple materials and scales. Here, various 3D printing strategies and the underlying mechanisms of functional magnetic materials for several primary applications are systematically reviewed, including, magnetic anisotropy for property enhancement, magnetic robots, magnetic components in electronics, and magneto-thermal devices. Finally, the current challenges and future perspectives in engineering 3D printed functional magnetic devices are discussed.

The fabrication of shape memory alloy (SMA) based products requires the precise bending and high-temperature training of SMA wires to obtain desired two-dimensional (2D) and three-dimensional (3D) patterns. In the typical fabrication process, SMA wire is bent and fixed in a pre-built mold and is trained using a furnace. However, in the small batch production, the fabrication of a mold that can be put in a high-temperature oven is costly and requires a long time to fabricate. A novel SMA wire bending process using vat photopolymerization (VPP) is presented in this paper. A rotary wire extruding system was designed to control the feeding speed of the fed wire and the bending of the wire into the desired shape. The wire bending process was enabled by utilizing a VPP tool that was immersed in liquid resin to selectively cure the resin to firmly fix the extruded SMA wire on a substrate. An air bubble assisted separation process was developed to address the separation of the cured resin from the immersed VPP tool. After the bending of the SMA wire into the desired shape, the SMA wire was connected to an electric current to heat the wire to a high temperature required by the training process so the SMA wire can memorize the fabricated pattern. Finally, the photocured fixtures deposited by the VPP tool were dissolved by a chemical solution and the bent SMA wire was detached from the fixture that was ready to use. The developed numerically controlled wire bending process is flexible for designed patterns and can fabricate SMA wires into 2D/3D shapes without specific molds or tedious manual work. Several test cases were performed to demonstrate the effectiveness of the newly developed SMA wire bending process.