Two-photon polymerization-assisted 3D laser nanoprinting: from fundamentals to modern applications

A key aspiration of modern science is to precisely control and arrange matter on a nanoscale level, creating 3D microstructures with specific functions. Microstereolithography technology has significantly pushed the frontiers of this aspiration, facilitating the manufacture of microdevices that offer innovative solutions in various sectors. Among different microstereolithography techniques, 3D laser nanoprinting based on two-photon polymerization (2PP) has emerged as a powerful tool for addressing complex challenges in a variety of scientific and industrial fields, with capabilities far exceeding those of traditional lithography techniques. Its unique ability to fabricate complex 3D microdevices with nanometer-scale precision has opened up new applications in a wide range of fields, including optics, electronics, and medicine. However, 2PP technology is still in its infancy, and many challenges have yet to be overcome, underscoring the need for further research and development to maximize the potential of 2PP lithography (2PL). This review aims to provide a comprehensive overview of 2PL, highlighting its fundamental background, experimental aspects, and various functional photoresists. Moreover, we review the fundamental principles underlying the exceptional spatial resolution and the key factors enhancing the feature resolution and surface accuracy of 2PP-printed microstructures. Finally, we explore diverse potential applications of 2PL across various disciplines and share current challenges, innovations, and future prospects in this field.