Reliable plasmonic biosensing with atmospheric pressure dielectric barrier discharge oxygen plasma treated polydimethylsiloxane microfluidic channels

Polydimethylsiloxane (PDMS) has emerged as a popular choice of material for many microfluidic and flexible sensing devices despite its inherent hydrophobic nature. Here, we report on the use of atmospheric pressure dielectric barrier discharge (APDBD) oxygen (O-2) plasma in the development of hydrophilic and protein repulsive PDMS microchannels for plasmonic sensing application. The effect of plasma treatment on the wettability, surface energy and hydrophilicity retention capacity of PDMS was determined using contact angle measurements. The PDMS sample exposed to low-power DBD O-2 plasma for 6 min demonstrated lowest contact angle of 35.15 & ring;, surface energy of 62.83 mN/m and hydrophilicity retention capacity of more than 50 days in Phosphate Buffered Saline (PBS). The treatment of PDMS with plasma induces surface hydrophilicity due to the introduction of polar functional groups as evinced by Fourier Transform Infrared (FTIR) analysis without compromising the bulk structure and optical properties of PDMS which were confirmed by X-Ray Diffraction (XRD) and Ultraviolet-visible (UV-Vis) Spectroscopic measurements. The plasma treated PDMS was used in the construction of a microfluidic Surface Plasmon Resonance (SPR) biosensor which demonstrated very low detection limits of 7.13 ng/ml, 5.91 ng/ml and 1.47 ng/ml and high sensitivities of 16.8 & ring;/(mu g/ml), 13.5 & ring;/(mu g/ml) and 16.65 & ring;/(mu g/ml) against anti-Human Immunoglobulin-G protein raised in mouse, goat and rabbit respectively. The obtained results infer that APDBD O-2 plasma is a promising technique to render PDMS hydrophilic suited for reliable microfluidic based plasmonic biosensing applications.