Advances in 3D nano/microfabrication using two-photon initiated polymerization

In recent years considerable efforts have been put forth in two-photon initiated polymerization (TPP)-based two- and three-dimensional (2D and 3D) nano/microfabrication for the development of novel nano/microdevices. In less than two decades of research, TPP has been employed in the fabrication of a great number of diverse micro-objects through the use of a wide variety of effective two-photon absorbing chromophores. In TPP, when a near-infrared ultrashort-pulsed laser is closely focused into a volume of photocurable resins, real 3D microstructures can be fabricated using a layer-by-layer accumulating technique making it a promising technique for 3D nano/microfabrication. More recently, a spatial resolution of sub-100 nm scale was achieved with TPP by employing a radical quenching mechanism. There also have been many studies that aimed at improving the fabrication efficiency and precision of TPP. Focus of ongoing research is the development of efficient two-photon absorbing chromophores. In this article, we discuss recent efforts in developing two-photon absorbing chromophores with focus on their structure property relationship and some recent outstanding attempts at improving the fabrication efficiency of 3D nano/microfabrications based on TPP.