title: Fabrication of 3-D curved microstructures by constrained gas expansion and photopolymerization.
abstract: This paper describes a novel method of fabricating three-dimensional (3-D) curved microstructures with continuous relief through controlled argon gas expansion into a photocurable resin. A microstructured stamp is placed on top of a nonwetting photopolymerizable liquid resin. The setup is heated, and the argon gas in the blind holes of the stamp expands. The expanded gas displaces the resin at the mouth of the microcavities to form 3-D curved indentations in the liquid resin which is subsequently rapidly solidified by photopolymerization. By changing the duration of the preheating, different curvatures can be produced. Arrays of homogeneous 3-D curved microstructures having different cross-sectional geometries and heights were fabricated using various shapes of the blind holes and preheating times, respectively. As a demonstration of applications, high-quality and uniform polydimethylsiloxane microlens arrays were produced. In addition, thorough investigation was carried out to study the factors influencing the fabricated 3-D curved microstructures. Curved microstructures with diameters as small as 2 microm were demonstrated. A simple model was developed, and such a model allows for predicting the curvatures of indentations with different preheating times. It has been found that the predicted curvatures are in good agreement with experimental data.
authors.affiliation: School of Chemical and Biomedical Engineering, Nanyang Technological University, 50 Nanyang Ave, Singapore 639798. mbechan@ntu.edu.sg
authors.forename: Mary B
authors.initials: MB
authors.lastname: Chan-Park
authors.forename: Chun
authors.initials: C
authors.lastname: Yang
authors.forename: Xun
authors.initials: X
authors.lastname: Guo
authors.forename: Lq
authors.initials: L
authors.lastname: Chen
authors.forename: Soon Fatt
authors.initials: SF
authors.lastname: Yoon
authors.forename: Jung-Hoon
authors.initials: JH
authors.lastname: Chun
mesh_terms: D001128:Argon / Q000737:chemistry; D001672:Biocompatible Materials; D004129:Dimethylpolysiloxanes / Q000737:chemistry; D005740:Gases; D008422:Materials Testing; D044085:Microfluidics; D008855:Microscopy, Electron, Scanning; D015233:Models, Statistical; D009757:Nylons / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D012826:Silicone Elastomers / Q000737:chemistry; D012828:Silicones / Q000737:chemistry; D013499:Surface Properties; D013696:Temperature; D014466:Ultraviolet Rays; D017155:Wettability
chemical_list: D001672:Biocompatible Materials; D004129:Dimethylpolysiloxanes; D005740:Gases; D009757:Nylons; D011108:Polymers; D012826:Silicone Elastomers; D012828:Silicones; C085707:poly(dimethylsiloxane)-polyamide copolymer; C013830:baysilon; D001128:Argon