基于胶体微球模板制备微透镜阵列

Abstract

A simple and efficient templating method in combination with hot embossing technique is developed for fabricating large-area two-dimensional (2D) microlens arrays (MLAs) with uniform shape. By utilizing a modified microchannel method, a 2D large-area hexagonal close-packed (HCP) array of silica colloidal microspheres is prepared and serves as a template in the following hot embossing treatment to create a polycarbonate (PC) microcavity array. Then, with the obtained PC microcavity structure serving as a mold, a hot embossing process is applied to finally achieve a polymethylmethacrylate (PMMA) MLA. The effect of annealing time during the mold preparation process on the dimensions and shapes of the prepared microlens is investigated. The imaging performances of the prepared PC concave microcavities and PMMA convex microlenses are characterized by carrying out projection experiments. Our method provides a rapid and low cost approach to prepare large-area MLAs.OCIS Microlens has been studied for decades due to its important applications in imaging, optic communication, and biochemical detection [1−7] . For example, compact all-fiber zone plate microlens fabricated at the end of a mode-expanded hybrid fiber can help focus emergent light remarkably [8,9] . With a pair of microlens arrays (MLAs), pupil densification can be achieved with improving the imaging performance of the hyper telescope [10] . Moreover, multidirectional asymmetrical MLAs have been fabricated and served as light-control films for enhancing the imaging quality of refractive liquid-crystal displays [11] . Up to now, many different approaches have been reported to fabricate MLAs with particular shape and dimension, including lithography-assisted thermal reflow process [12−19] , gray-scale lithography [20,21] , allliquid techniques [22−24] , and mask-assisted focus-ionbeam lithography [25,26] . However, the aforementioned methods more or less require complex experimental processes or expensive equipments. By contrast, the selforganization technique, commonly used for preparing masks or templates [27−29] , has provided a new way for fabricating MLAs with low cost and simple procedure. For example, Yabu et al. [30] have reported the preparation of hexagonally packed micropores structure by using self-assembled condensed water droplets as templates. Spherical MLAs have been successfully fabricated by directly molding from the resulting 'honeycomb' structure.In this letter, we present a simple and efficient templating method to fabricate large-area MLAs with uniform shape. Our method comprises two processes which are mold preparation and subsequent hot embossing. We show that the size control of the fabricated microlens can be achieved by varying the annealing time during mold preparation process or the size of the colloidal particles. Imaging performances of both polycarbonate (PC) concave and polymethylmethacrylate (PMMA) convex microlens prepared are further characterized and the image resolution is improved through tuning the dimensions of microl...