Hydrophobicity Recovery of Polydimethylsiloxane Treated with Oxygen Plasma and Ion Implantation

Abstract

One of a few disadvantage properties of polymethylsiloxane (PDMS) is its hydrophobicity which can hinder its fluidic applications. Oxygen plasma treatment on PDMS surfaces is a conventional method in rendering them hydrophilic, however hydrophobicity returns within days after treatment. This study proposes oxygen ion implantation at the micrometer scale inside PDMS structures to ensure lasting hydrophilicity. The PDMS slabs were treated with 20 keV oxygen ion with 1 × 1015 ions/cm2 fluence and inductively coupled oxygen plasma generated at a power of 28 W and frequency of 13.56 MHz. The chemical composition of the treated PDMS surface was monitored by X-ray photoelectron spectroscopy (XPS) and it was found that oxygen concentration remain high after three days of oxygen plasma treatment on the PDMS. Although the surface oxygen concentration in the oxygen ion implanted PDMS was not as high as that oxygen plasma treated PDMS, the oxygen concentration level was remained higher than that of the untreated PDMS surface for four weeks.