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Self-Organized Wrinkling in Thin Polymer Films under Solvent–Nonsolvent Solutions: Patterning Strategy for Microfluidic Applications

Research output: Contribution to Journal/MagazineJournal articlepeer-review

Published
  • Naval Singh
  • Ankur Verma
  • Priyanka Sachan
  • Ashutosh Sharma
  • Manish M. Kulkarni
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<mark>Journal publication date</mark>10/12/2021
<mark>Journal</mark>ACS Applied Polymer Materials
Issue number12
Volume3
Number of pages9
Pages (from-to)6198-6206
Publication StatusPublished
Early online date15/11/21
<mark>Original language</mark>English

Abstract

Self-organized wrinkling instabilities in thin polymer films have instigated a field of versatile surface patterning and have spurred several research efforts in developing micro- and nanopatterned templates for a wide range of applications. Here, we report for the first time a distinct class of wrinkles in a thin polymer (polystyrene, PS) film coated on a substrate under a mixture of organic solvent and aqueous nonsolvent. The solvent (dimethyl formamide, DMF) softens and swells the polymer and paves the way for wetting of the hydrophilic substrate (≥46 mJ/m2) by the solvent–nonsolvent (S-NS) mixture, leading to wrinkle formation. It is investigated that selective delamination-induced wrinkling is a generic phenomenon and takes place in various polymers as well as different combinations of solvent–nonsolvent mixtures. The surface energy of the substrate and the composition of the solvent–nonsolvent mixture play a critical role as wrinkling is not observed on substrates with lower surface energy (<46 mJ/m2). An isotropically distributed yet disordered self-organized wrinkle network of hollow buried channels is formed, and it is illustrated that these can be exploited to generate a mesh of microwires and harnessed to form highly directional patterns using electron beam lithography, which can turn the new leaf for nano- and microfluidic device fabrication platforms.