Special Issue Editorial: Advanced Materials for Additive Manufacturing

摘要

Additive manufacturing (AM or 3D printing) has advanced significantly over the past decade and has seen a proliferation of new materials, new methods, and new applications. As AM is fundamentally a material processing technology, its advance closely relates to materials. This special issue consists of 32 articles from renowned groups worldwide, presenting their perspective and recent advancements in AM. The articles cover a wide range of topics, which reflect the diversity and breadth of the AM field. The collections in this special issue have attracted seven review articles that cover different aspects of the AM field. Zhu et al. (adma.202314204) discussed the recent progress in multi-material and multi-scale AM. Chen et al. (adma.202307686) also explored multimaterial 3D/4D printing for tissue engineering applications. Wan et al. (adma.202312263) reviewed the latest achievements in 4D printing across diverse fields, including biomedical engineering, electronics, robotics, and photonics. Machine learning has immersed into different fields, including AM. Ng et al. (adma.202310006) discussed the challenges and opportunities of integrating machine learning with AM, including quality control, process optimization, design optimization, microstructure analysis, and material formulation, etc. Laser is one of the most commonly used energy sources for AM. Park et al. (adma.202307586) discussed the principle, material selection, and applications of laser-based AM. The progress of AM also significantly advances other fields, such as soft robotics. Xin et al. (adma.202307963) provided an overview of how AM promotes the fabrication of soft grippers, which are an important component of soft robots. Tissue engineering applications are another sub-field where AM finds tremendous potential. Yuan et al. (adma.202403641) presented an in-depth review of 3D printing of smart scaffolds with stimulus-responsive properties, which can generate tailored and controllable therapeutic effects for bone tissue engineering and regeneration. This special issue has a strong focus on materials in 3D printing. Liquid crystal elastomers (LCEs) have attracted significant attention in recent years due to their capability of large reversible actuation upon external stimuli. LCEs are typically actuated by heat. However, typical heating methods, such as water baths, are relatively slow. Maurin et al. (adma.202302765) proposed an LCE-liquid metal (LM) composite where the LM was used to heat the 3D-printed LCEs ultrarapidly through eddy current under a high-frequency magnetic field. In their demonstrations, the LCE structures could be activated in less than a second. Photothermal heating by incorporating nanoparticles into resin is another common method for LCE actuators. Gold nanorods (AuNRs) are typically used due to their high photothermal efficiency. Skillin et al. (adma.202313745) grafted AuNR with poly(ethylene glycol) (PEG) that greatly improved the dispersion of AuNR in the LCE resin. Because of this, the LCE-AuNR nanocomposites with very low PEG-AuNR content (0.01 wt.%) were shown to be highly efficient photothermal actuators with rapid response (within a second). Chen et al. (adma.202303969) incorporated photochromic titanium-based nanocrystals (TiNC) into an LCE ink. Upon UV irradiation, TiNC could change color from white to black and absorb infrared (IR) light to generate heat. The 3D-printed structures could thus be globally or locally programmed, erased, and reprogrammed for color and shape change. Kotikian et al. (adma.202310743) used a multi-nozzle 3D printer to fabricate LCE lattice structures with spatially programmed nematic director order. These structures demonstrated different interesting shape morphing upon actuation. Escobar and White (adma.202401140) developed actuators by twisting LCE fibers. These actuators showed dramatically increased deformation rate, specific work, and achievable force output. Liquid metals , because of their high conduct