Investigation into nano-stereolithography process for fabrication of precise three-dimensional microstructures

Abstract

Fabrication techniques of nano-patterns and three-dimensional (3D) microstructures are of great importance in diverse fields of modern technology, such as nanotechnology (NT), biotechnology (BT), and information technology (IT), for the development of highly functional applications: micro/nanofluidic devices, biochips, photonic crystals, and nano/micro-electromechanical systems (N/MEMS). For these purposes, many novel 3D microfabrication techniques have been developed, for examples, microstereolithography, nano-imprint lithography, soft-lithography, electrochemical fabrication (EFAB), localized electrochemical deposition, LIGA process, and many others. Using these techniques, diverse micro-devices can be built with various engineering materials such as polymers, metals, and ceramics. However, most of the existing microfabrication processes, except the microstereolithography, were developed for two-dimensional (2D) based microfabrication, thus they do not have the ability to build completely real 3D microstructures which are applicable to neo-conceptive devices. Recently, considerable efforts focusing on two-photon polymerization (TPP) have been put forth in the area of 2D and 3D nano/microfabrication. Since TPP first came out as a novel technique over a decade ago, a great number of micro-objects have been fabricated using TPP with a variety of effective two-photon 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; therefore, TPP is considered to be a promising technique for real 3D nano/microfabrication. Recent reports have shown that the spatial resolution of TPP is achieved at approximately sub-100 nm scale employing a radical quenching mechanism, and a few studies have been carried out especially based on improving the fabrication efficiency and precision of TPP. In addition, many research wor...