Fabrication of three-dimensional nanostructures within microfluidic chips by prism holographic lithography

Abstract

Holographic lithography (HL) based on the interference of multiple coherent laser beams has been used to fabricate a large variety of three-dimensional (3D) photonic crystal (PC) templates with defect free, submicrometer scale structures over large area. However, this fabrication strategy can introduce alignment complexity and inaccuracies due to the differences in the optical path length and angles among the interfering beams as well as vibrational instabilities in the optical setup, which results in the distortion and blur of the 3D structure. In order to improve optical setup, a single optical element, such as a specially-designed prism and a phase mask has been introduced to create interference pattern of the multiple interfering beams from a single laser beam through refraction, diffraction, or total internal reflection. Here, I describe the fabrication of 3D periodic structures with face-centered-cubic (FCC) and diamondlike woodpile symmetry by using single prism holographic lithography. Holographic lithography in combination with photolithography provides a novel optofluidic platform through incorporation of periodic photonic units inside the microfluidic chips in a highly compatible and facile way. Mixing units of 3D interconnected pore network inside microfluidic channels are also incorporated by combining single prism holographic lithography and photolithography. The detailed fabrication process and the modulation of photonic band gap in response to the change in the refractive indices of the flowing media in the microfluidic chips are discussed in Chapter 2.1. Also, the mixing performance of the 3D porous structures in the microfluidic chips is studied in Chapter 2.2. In Chapter 3, I present an intriguing method for fabricating polymeric superhydrophobic surfaces by reactive-ion etching of holographically featured 3D structures. Using the proposed strategy, I generate both lotus (high contact angle and weak adhesion force) and gecko (high contac...