Open AccessLarge-area fabrication of microlens arrays by using self-pinning effects during the thermal reflow process
Author(s) -
Seong Gil Heo,
Dong Kee Jang,
HyungJun Koo,
Hyunsik Yoon
Publication year - 2019
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.27.003439
Subject(s) - microlens , materials science , fabrication , optics , nanoimprint lithography , lithography , resist , curvature , substrate (aquarium) , lens (geology) , thermal , optoelectronics , photolithography , nanolithography , focal length , nanotechnology , medicine , oceanography , physics , alternative medicine , geometry , mathematics , pathology , layer (electronics) , geology , meteorology
Generally, the fabrication of curved structures such as microlens arrays has been regarded as an expensive and complicated process. Here, we propose a facile method to form a microlens array with controlled lens curvature by combining residue-free nanoimprint lithography (NIL) with V-shaped molds and the successive thermal reflow procedure of the printed polymeric structures. The V-shaped molds used in this study enable the bottom substrate to be exposed after the NIL process when the initial thickness is controlled. Then, we use the thermal reflow to realize hemi-cylindrical curved lenses by applying heat. The polymers are self-pinned on the exposed substrate, which is strong enough to fix the boundary to not dewet or be flattened in the broad temperature range of the reflow process, which is essential for a large-area fabrication. Furthermore, we demonstrate the modulation of the focal lengths of the lenses by controlling the initial polymer thickness coated on a substrate.