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Abstract Ionogels are promising material candidates for ionotronics due to their excellent ionic conductivity, stretchability, and thermal stability. However, it is challenging to develop 3D printable ionogels with both excellent electrical and mechanical properties. Here, we report a highly conductive and stretchable nanostructured (CSN) ionogel for 3D printing ionotronic sensors. We propose the photopolymerization-induced microphase separation strategy to prepare the CSN ionogels comprising continuous conducting nanochannels intertwined with cross-linked polymeric framework. The resultant CSN ionogels simultaneously achieves high ionic conductivity (over 3 S m−1), high stretchability (over 1500%), low degree of hysteresis (0.4% at 50% strain), wide-temperature-range thermostability (−72 to 250 °C). Moreover, its high compatible with DLP 3D printing enables the fabrication of complex ionogel micro-architectures with high resolution (up to 5 μm), which allows us to manufacture capacitive sensors with superior sensing performances. The proposed CSN ionogel paves an efficient way to manufacture the next-generation capacitive sensors with enhanced performance.

Abstract 4D printing technology combines 3D printing and stimulus-responsive materials, enabling construction of complex 3D objects efficiently. However, unlike smart soft materials, 4D printing of ceramics is a great challenge due to the extremely weak deformability of ceramics. Here, we report a feasible and efficient manufacturing and design approach to realize direct 4D printing of ceramics. Photocurable ceramic elastomer slurry and hydrogel precursor are developed for the fabrication of hydrogel-ceramic laminates via multimaterial digital light processing 3D printing. Flat patterned laminates evolve into complex 3D structures driven by hydrogel dehydration, and then turn into pure ceramics after sintering. Considering the dehydration-induced deformation and sintering-induced shape retraction, we develop a theoretical model to calculate the curvatures of bent laminate and sintered ceramic part. Then, we build a design flow for direct 4D printing of various complex ceramic objects. This approach opens a new avenue for the development of ceramic 4D printing technology.

Thick panel origami holds great potential in engineering structures, but conventional fabrication processes limit their design and applications. Here the authors report a multimaterial 3D printing-based design and fabrication strategy for thick-panel origami structures with push-to-pull deformation.

Nowadays, the combined offshore wind farm and hydrogen production plant (COWHP) has been installed all around the world and will play an important role in reducing the carbon dioxide emissions. However, the cooperation of the COWHP, the hydrogen pipeline transportation, the power network transmission, and the hydrogen fuel cell electric vehicles (HFCEVs) scheduling is still an essential problem. This problem falls into the category of mixed-integer nonlinear optimization, which involves a significant number of decision variables and constraints. Existing methods have often struggled to effectively solve this problem due to its inherent complexity and non-linear nature. In this paper, a price-guided method is proposed to cooperate with this complex system. First, the COWHP model, the hydrogen pipeline network scheduling model, the power network flow model, the HFCEVs refuelling microgrid model, and the HFCEV traffic flow model in real-world transportation networks are presented. Second, the price-based cooperation model is proposed. Third, price strategies are deployed to cooperate with the complex system. The decision making trial and evaluation laboratory-the technique for order preference by similarity to ideal solution (Dematel-TOPSIS) method is deployed to evaluate the real-time performance of different strategies. The simulation results reveal that in the small vehicle flow transportation network cases, deep deterministic policy gradient (DDPG) has the best real-time evaluation performance; whereas for the large vehicle flow transportation network cases, long short term memory (LSTM) has the best real-time performance. From the posterior evaluation view, LSTM has the best performance for all cases to reduce total operation cost, and also reduce the total waiting time.

Multimaterial 3D printing using digital light processing (DLP) is challenging because multimaterial switching methods require direct contact onto the printed part to remove residual resin. Here, the authors report a DLP-based centrifugal multimaterial 3D printing method to generate large-volume heterogeneous 3D objects where composition, property and function are programmable at voxel scale.

The integration of additive manufacturing (AM) in design and engineering has prompted a wide spectrum of research efforts, involving topologically optimized solid/lattice structures, multimaterial structures, bioinspired organic structures, and multiscale structures, to name a few. However, except for obvious cases, very little attention has been given to the design and printing of more complex three-dimensional (3D) hollow structures or folded/creased structures. One of the main reasons is that such complex open or closed 3D cavities and regular/freeform folds generally lead to printing difficulties from support-structure-related issues. To address this barrier, this paper aims to investigate four-dimensional (4D) printing as well as origami-based design as an original research direction to design and build 3D support-free hollow structures. This work consists of describing the rough 3D hollow structures in terms of two-dimensional (2D) printed origami precursor layouts without any support structure. Such origami-based definitions are then embodied with folding functions that can be actuated and fulfilled by 3D printed smart materials. The desired 3D shape is then built once an external stimulus is applied to the active materials, therefore ensuring the transformation of the 2D origami layout to 3D structures. To demonstrate the relevance of the proposal, some illustrative cases are introduced.

Two-photon polymerization (TPP) is a cutting-edge micro/nanoscale three-dimensional (3D) printing technology based on the principle of two-photon absorption. TPP surpasses the diffraction limit in achieving feature sizes and excels in fabricating intricate 3D micro/nanostructures with exceptional resolution. The concept of 4D entails the fabrication of structures utilizing smart materials capable of undergoing shape, property, or functional changes in response to external stimuli over time. The integration of TPP and 4D printing introduces the possibility of producing responsive structures with micro/nanoscale accuracy, thereby enhancing the capabilities and potential applications of both technologies. This paper comprehensively reviews TPP-based 4D printing technology and its diverse applications. First, the working principles of TPP and its recent advancements are introduced. Second, the optional 4D printing materials suitable for fabrication with TPP are discussed. Finally, this review paper highlights several noteworthy applications of TPP-based 4D printing, including domains such as biomedical microrobots, bioinspired microactuators, autonomous mobile microrobots, transformable devices and robots, as well as anti-counterfeiting microdevices. In conclusion, this paper provides valuable insights into the current status and future prospects of TPP-based 4D printing technology, thereby serving as a guide for researchers and practitioners.

Soft materials exhibiting unique nonlinear mechanical behavior with large deformation are ubiquitous in nature. In addition, there is a type of soft active materials (SAMs) that can undergo large mechanical deformation. In recent years, soft materials have been developed for impactful applications in aerospace, biomedical devices, and soft robots. However, the traditional manufacturing approaches greatly limit the functionality and performance of structures and devices made of soft materials. 3D printing as an emerging advanced manufacturing technology is considered as an ideal tool to manufacture soft materials. Compared with other 3D printing technologies, digital light processing (DLP)-based 3D printing fabricates 3D objects by localized photopolymerization, and is capable of fabricating 3D objects with highly complex geometries and high resolution. Recently, DLP-based 3D printing has demonstrated its excellent compatibility with a variety of soft materials, and is capable of manufacturing these soft materials into 3D structures and devices with complex geometries, high resolution and unique performance. This reviewer article presents a brief but timely introduction to the most recent advances in DLP-based 3D printing of soft materials.

4D printing enables 3D printed structures to change shape over "time" in response to environmental stimulus. Because of relatively high modulus, shape memory polymers (SMPs) have been widely used for 4D printing. However, most SMPs for 4D printing are thermosets, which only have one permanent shape. Despite the efforts that implement covalent adaptable networks (CANs) into SMPs to achieve shape reconfigurability, weak thermomechanical properties of the current CAN-SMPs exclude them from practical applications. Here, we report reconfigurable 4D printing via mechanically robust CAN-SMPs (MRC-SMPs), which have high deformability at both programming and reconfiguration temperatures (>1400%), high Tg (75°C), and high room temperature modulus (1.06 GPa). The high printability for DLP high-resolution 3D printing allows MRC-SMPs to create highly complex SMP 3D structures that can be reconfigured multiple times under large deformation. The demonstrations show that the reconfigurable 4D printing allows one printed SMP structure to fulfill multiple tasks.. [ABSTRACT FROM AUTHOR]