Lithography: Fabrication of Hierarchical Pillar Arrays from Thermoplastic and Photosensitive SU‐8 Small 6/2010

Abstract

The cover image illustrates an array of high-aspect-ratio (up to 7.7) polymer pillars from SU-8 photoresists imprinted by capillary force lithography (CFL), followed by photopatterning and a thermal reflow process. Because of the thermoplastic nature of SU-8, pillars with variable aspect ratios are created through CFL using a single poly(dimethylsiloxane) membrane as the mold, simply by tuning the initial film thickness of SU-8 on a substrate. The pillars are subsequently photopatterned through a photomask with a square dot array, followed by post-exposure bake above the glass-transition temperature (Tg) of SU-8. The pillars in the exposed region become highly crosslinked, and thus neither soluble nor reflowable, whereas the pillars in the unexposed regions can reflow and flatten out above Tg. In this way, a single-level, dual-scaled, high-aspect-ratio SU-8 pillar array is “developed” in the exposed region without the use of solvent. Such high-aspect-ratio pillar arrays may find applications in biomimetic superhydrophobic surfaces and dry adhesion, microfluidics, diagnosis, tissue engineering, force sensing, and actuation. For more information, please read the Full Paper “Fabrication of Hierarchical Pillar Arrays from Thermoplastic and Photosensitive SU-8” by S. Yang et al., beginning on page 768.