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      https://www.ias.ac.in/article/fulltext/boms/043/0186

    • Keywords

       

      PDMS; hydrophobicity; UVO exposure; soft lithography; patterning.

    • Abstract

       

      Cross-linked polydimethylsiloxane (PDMS) films and surfaces obtained by thermal cross-linking of commercially available Sylgard 184 are widely utilized in many areas of science, due to superior thermal stability, low dielectric constant, transparency and biocompatibility. Cross-linked PDMS surfaces are weakly hydrophobic and several experiments, particularly the ones that utilize capillary-driven microscale flow require the modulation of the surface wettability. A well-known strategy to achieve the same is by exposing the Sylgard 184 surface to UV/ozone (UVO) treatment at room temperature. Depending on the duration of exposure, the wettability drops from hydrophobic to a nearcompletewetting (water contact angle $\sim$10$^{\circ}$), due to the formation of a surface oxide layer. However, under normal atmospheric conditions, these surfaces recover their hydrophobicity over a period of time due to diffusive migration of the uncrosslinked oligomers to the surface, and formation of a hydrophobic dimethyl silicone layer. We explore the hydrophobic recovery process as a function of cross-linker concentration and UVO exposure time and show how a partially or fully recovered PDMS stamp may influence subsequent nanopatterning, including the possible creation of features with different morphology using a single stamp.

    • Author Affiliations

       

      NANDINI BHANDARU1 2 NEHA AGRAWAL1 MENEKA BANIK1 RABIBRATA MUKHERJEE1 ASHUTOSH SHARMA3

      1. Instability and Soft Patterning Laboratory, Department of Chemical Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
      2. Department of Chemical Engineering, BITS Pilani, Hyderabad Campus, Hyderabad 500078, India
      3. Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India
    • Dates

       
  • Bulletin of Materials Science | News

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