A cost-effective two-step method for enhancing the hydrophilicity of PDMS surfaces

Abstract

Poly(dimethylsiloxane) (PDMS) is commonly used for fabricating micro- and nanofluidic devices due to its low cost and ease of fabrication. The major disadvantage to using PDMS for these applications is its hydrophobic properties. The current methods that enhance the hydrophilicity of elastomers used for micro- and nanofluidic applications are intricate and cost-inefficient. This contribution demonstrates how the hydrophobic PDMS surface can be chemically modified in 5 minutes using a two-step silanization method in an oxygen-saturated environment to provide a highly stable hydrophilic surface for irreversible PDMS to PDMS bonding and PDMS to borosilicate glass bonding. The surface wettabilities of the modified and pristine PDMS were characterized over a wide range of time using static contact angle measurements. The modified PDMS surfaces exhibit enhanced stable hydrophilicity with a contact angle of 87° for 5 days. Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectra of the modified and pristine PDMS surfaces confirmed the presence of hydroxyl groups of water molecules in the modified PDMS at 3150 cm−1 in addition to the characteristic peaks of pristine PDMS. This reliable silane beaker chemistry-based method allows easy bonding of the PDMS surfaces for liquid containment and irreversible bonding to borosilicate glass. This approach can effectively be adapted for enhancing the hydrophilicity of PDMS, which ensure relevance for current and future micro- and nanofluidic applications.