Two-photon stereolithography for realizing ultraprecise three-dimensional nano/microdevices

Two-photon stereolithography (TPS) provides many advantages for achieving two-dimensional (2D) and three-dimensional (3D) micrometer-scale polymeric, ceramic and metallic structures applicable to complicated optical and neoelectronic microdevices. In the fabrication of high-resolution 3D microstructures, TPS has significant advantages over conventional microelectromechanical system (MEMS) processing, which involves time-consuming multistep indirect fabrication processes. Many studies have recently been made to develop and improve the TPS process, focusing on creating greater efficiency, higher resolution, and greater productivity, which are essential requirements of a practical TPS process. For the first time, an artistic microstructure has recently been successfully produced with an ultraprecise spatial resolution, sub-30 nm nanofibers, 3D multilayer imprint stamps for mass production, and ceramic 3D microstructures. In this review, we report the progress of two-photon polymerization based on 3D micro fabrication, including the results obtained from the original research. This report is presented in three sections: improvement of resolution, precise design schemes, and applications of 3D microstructures.