Recent Advances in Two-Photon Lithography of 3D Inorganic Microstructures: Glass, Ceramics, Metals, and Carbon

The fabrication of intricate three-dimensional (3D) inorganic microstructures - including glass, ceramics, metals, and carbon - is essential for next-generation devices in MEMS, photonics, energy storage, and biointerfaces. However, simultaneously achieving sub-micron resolution, true 3D geometric complexity, and high-performance inorganic material conversion remains a major manufacturing challenge for conventional additive and subtractive techniques. In the past two decades, two-photon lithography (TPL) has emerged as a powerful solution to this fabrication bottleneck. By leveraging nonlinear two-photon absorption, TPL enables voxel-level fabrication of intricate precursor scaffolds with remarkable geometric freedom and resolution, which can then be transformed into functional inorganic microstructures through controlled pyrolysis, annealing, or sintering. This review provides a comprehensive overview of TPL as a promising platform for 3D inorganic microfabrication. We systematically analyze precursor design principles, photochemical mechanisms, and the chemical and structural evolution during thermal processing. Representative applications in optics, mechanical metamaterials, micro electrodes, and biomedical interfaces are highlighted. Finally, we discuss current challenges, including shrinkage control, throughput limitations, and material diversity, and outline future opportunities such as low-temperature post-treatment, multi-material integration, artificial intelligence-assisted design and manufacturing, and cross-scale manufacturing strategies.