Fabrication of strain responsive microlens array by confined buckling of poly(dimethylsiloxane) bilayer structure

PMSE 148

Dinesh Chandra1, Pei-Chun Lin2, and Shu Yang, shuyang@seas.upenn.edu1. (1) Department of Materials Science and Engineering, University of Pennsylvania, 3231 Walnut Street, Philadelphia, PA 19104, (2) Department of Mechanical Engineering, National Taiwan University, No. 1 Roosevelt Rd. Sec. 4, Taipei, Taiwan
Variable-focus microlens arrays are of interest for optical communication, MEMS devices and sensors. Most of the existing tunable microlens arrays are multi-component systems, and require complex fabrication and assembly processes. Here, we report fabrication of single-component, strain responsive, variable-focus microlens array (concave and convex) with real-time tunability. The concave microlens array was created by mechanical force induced confined buckling of a soft elastomer, poly(dimethylsiloxane) (PDMS), coated with a thin layer of hard layer oxide. Convex microlens array was replica-molded from the concave microlens array in PDMS. We demonstrate continuous change of focal length (up to 1.6 times) of the microlens arrays, dependent on the applied mechanical strain to the lenses and the pre-strain in lens fabrication. Because of the mechanistic difference in formation of the two types of lenses, much larger focal length tunability is obtained from buckled concave microlens array in comparison to that from replica-molded convex microlens array.