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Fabrication of Hierarchical Pillar Arrays from Thermoplastic and Photosensitive SU‐8
Author(s) -
Zhang Ying,
Lin ChiaTai,
Yang Shu
Publication year - 2010
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.200901843
Subject(s) - pillar , materials science , fabrication , thermoplastic , photomask , lithography , aspect ratio (aeronautics) , mold , substrate (aquarium) , thermoforming , nanotechnology , composite material , photolithography , resist , optoelectronics , layer (electronics) , mechanical engineering , medicine , oceanography , alternative medicine , pathology , geology , engineering
By exploiting the thermoplastic and photosensitive nature of SU‐8 photoresists, different types of hierarchical pillar arrays with variable aspect ratios are fabricated through capillary force lithography (CFL), followed by photopatterning. The thermoplastic nature of SU‐8 enables the imprinting of micropillar arrays with variable aspect ratios by CFL using a single poly(dimethylsiloxane) mold, simply by tuning the initial film thickness of SU‐8 on a substrate. The pillar array is subsequently photopatterned through a photomask, followed by post‐exposure baking above the glass transition temperature ( T g ) of SU‐8. The pillars in the exposed region become highly crosslinked and, therefore, neither soluble nor able to reflow above T g , whereas the pillars in the unexposed regions can reflow and flatten out. Two developing strategies are investigated after UV exposure of the SU‐8 pillar arrays including i) solvent development and drying and ii) thermal reflow to create bilevel hierarchical structures with short pillars and single‐level, dual‐scaled, high‐aspect‐ratio (up to 7.7) pillars in a microdot array, respectively.