Hierarchical Micro/Nano Structures by Combined Self-Organized Dewetting and Photopatterning of Photoresist Thin Films

Abstract

Photoresists are the materials of choice for micro/nanopatterning and device fabrication but are rarely used as a self-assembly material. We report for the first time a novel interplay of self-assembly and photolithography for fabrication of hierarchical and ordered micro/nano structures. We create self-organized structures by the intensified dewetting of unstable thin (∼10 nm to 1 μm) photoresist films by annealing them in an optimal solvent and nonsolvent liquid mixture that allows spontaneous dewetting to form micro/nano smooth dome-like structures. The density, size (∼100 nm to millimeters), and curvature/contact angle of the dome/droplet structures are controlled by the film thickness, composition of the dewetting liquid, and time of annealing. Ordered dewetted structures are obtained simply by creating spatial variation of viscosity by ultraviolet exposure or by photopatterning before dewetting. Further, the structures thus fabricated are readily photopatterned again on the finer length scales after dewetting. We illustrate the approach by fabricating several three-dimensional structures of varying complexity with secondary and tertiary features.

Droplet Microarrays: From Surface Patterning to High‐Throughput Applications

“…The method of polymer film dewetting has been used for polymer deposition. [74][75][76][77] As an example, a vapor-induced dewetting of SU-8 thin film on hydrophobic-hydrophilic patterned PDMS substrates was reported by Bi et al [77] The cyclopentanone vapor broke up the spin-coated SU-8 film where the defect positions existed and initiated dewetting, while dewetted SU-8 droplets spontaneously organized on hydrophilic spots to form well-aligned polymer arrays. Upon miniaturization, these types of methods, based on bottom-up self-assembly driven effects rather than on top-down pipetting into microwells, become important.…”

Dewetting Metal Nanofilms—Effect of Substrate on Refractive Index Sensitivity of Nanoplasmonic Gold

“…The thickness of Au film was confirmed with atomic force microscopy (AFM) after establishing the tooling factors of the evaporator as also described in literature reports [27,28]. The Au thin films were then annealed at 560 °C for 3 h to produce AuNI on these supporting substrates [4,29]. The fabricated AuNI nanoplasmonic substrates were integrated with Polydimethylsiloxane (PDMS) wells.…”

Dewetting of Thin Lubricating Films Underneath Aqueous Drops on Slippery Surfaces

“…Thin polymer film used as the lubricating fluid in slippery surfaces often becomes unstable (dewetting) on solid surfaces due to its interaction with the substrate and test liquid by long-range interaction, short-range polar interaction, and other molecular forces [14,15]. Despite the * kcharya@iitk.ac.in large applications of the system when drop floats, instability pattern arises by rupturing of the film when the drop sinks, used in many applications like protein patterning, cell culture, contact lens production, and water harvesting [16][17][18][19][20][21][22][23][24].…”