The bubbles formed on the electrodes tend to stick to the reaction area during hydrogen (H₂) production, hindering the continuous reaction, which drastically reduces the H₂ production efficiency. In this work, a customizable multifunctional three-dimensional (3D) electrode with bionic structures is proposed and precisely fabricated by the projection microstereolithography (PμSL) 3D printing technique, which facilitates the catalytic reaction and the detachment of H₂ bubbles with an asymmetrically wetted bioinspired functional membrane to allow bubbles to pass through based on Janus effects. The 3D bionic functional electrodes exhibit excellent H₂ production performance. At the same voltage, the current density of our 3D electrode is 2.5 times greater than that of a two-dimensional (2D) electrode and 8 times greater than that of a one-dimensional (1D) common flat electrode with the same surface area. Moreover, the amount of H₂ collected from a 3D bionic functional electrode is 53.9% and 172.1% greater than that collected from 2D and 1D electrodes with the same catalyst size, respectively. Significantly, a 400 cm² panel reactor system based on biomimetic 3D functional electrodes enables one-week continuous operation with ultra-high safety and durability in H₂ production. Coupled with a solar panel, it achieves long-term outdoor H₂ production and gas collection.

Gradient refractive index (GRIN) metalenses are increasingly valued in high-frequency communication due to their exceptional radiation performance. Ceramics with high dielectric constants and low dielectric losses are ideal candidates for GRIN metalenses. Digital light processing (DLP) 3D printing provides a feasible and efficient approach for manufacturing ceramic GRIN metalenses. However, the scattering of ultraviolet (UV) light by ceramic particles in the slurry reduces the printing accuracy of DLP technology, making it difficult to achieve the intricate structural features required for GRIN metalenses in high-frequency communication. In this work, we propose an approach to improve printing accuracy by optimizing the ceramic slurry composition and implementing a dimensional compensation design strategy. Utilizing geometric optics and the S-parameter inversion method, we design a GRIN metalens consisting of two distinct types of subwavelength unit cells (Y-shaped and circular hole geometries) with a minimum feature size of 160 μm. Through a refined slurry formulation and precise design parameter compensation, high-fidelity ceramic GRIN metalenses are successfully fabricated. The fabricated metalens exhibits a maximum gain enhancement of 18.4 dBi and a deflection angle of ±30° over a bandwidth of 37.84% in the W-band (75‒110 GHz). The highly directional far-field beam radiation and efficient beam steering capabilities highlight the potential of ceramic GRIN metalenses for applications in satellite communications, radar systems, and other high-frequency technologies.

Organohydrogel-based strain sensors are gaining attention for real-time health services and human-machine interactions due to their flexibility, stretchability, and skin-like compliance. However, these sensors often have limited sensitivity and poor stability due to their bulk structure and strain concentration during stretching. In this study, we designed and fabricated diamond-, grid-, and peanut-shaped organohydrogel based on positive, near-zero, and negative Poisson’s ratios using digital light processing (DLP)-based 3D printing technology. Through structural design and optimization, the grid-shaped organohydrogel exhibited record sensitivity with gauge factors of 4.5 (0–200% strain, ionic mode) and 13.5/1.5 × 10⁶ (0−2%/2%−100% strain, electronic mode), alongside full resistance recovery for enhanced stability. The 3D-printed grid structure enabled direct wearability and breathability, overcoming traditional sensor limitations. Integrated with a robotic hand system, this sensor demonstrated clinical potential through precise monitoring of paralyzed patients’ grasping movements (with a minimum monitoring angle of 5°). This structural design paradigm advanced flexible electronics by synergizing high sensitivity, stability, wearability, and breathability for healthcare, and human-machine interfaces.

Multimaterial (MM) 3D printing shows great potential for application in metamaterials, flexible electronics, biomedical devices and robots, since it can seamlessly integrate distinctive materials into one printed structure. Among numerous MM 3D printing technologies, digital light processing (DLP) MM 3D printing is compatible with a wide range of materials from hydrogels to ceramics, and can print MM 3D structures with high resolution, high complexity and fast speed. This paper introduces the fundamental mechanisms of DLP 3D printing, and reviews the recent advances of DLP MM 3D printing technologies with emphasis on material switching methods and material contamination issues. It also summarizes a number of typical examples of DLP MM 3D printing systems developed in the past decade, and introduces their system structures, working principles, material switching methods, residual resin removal methods, printing steps, as well as the representative structures and applications. Finally, we provide perspectives on the directions of the further development of DLP MM 3D printing technology.

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.

Projection micro stereolithography (PμSL) is a high-resolution (up to 0.6 μm) 3D printing technology based on area projection triggered photopolymerization, and capable of fabricating complex 3D architectures covering multiple scales and with multiple materials. This paper reviews the recent development of the PμSL based 3D printing technologies, together with the related applications. It introduces the working principle, the commercialized products, and the recent multiscale, multimaterial printing capability of PμSL as well as some functional photopolymers that are suitable to PμSL. This review paper also summarizes a few typical applications of PμSL including mechanical metamaterials, optical components, 4D printing, bioinspired materials and biomedical applications, and offers perspectives on the directions of the further development of PμSL based 3D printing technology.