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.

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.