Stiffening of polydimethylsiloxane surface as result of exposure to low-pressure argon discharge plasma

Polydimethylsiloxane (PDMS) surface has been exposed to negative glow discharge plasma of a low-pressure discharge in pure argon for a duration varying from 10 s to 2 min. Shallow atomic force microscopy indentation experiments were performed to investigate the effect of plasma treatment on PDMS surface stiffness and adhesion energy to the silicon nitride indenter surface. The results showed an important increase in Young's modulus and a slight increase of work of adhesion. X-ray photoelectron spectroscopy investigation of plasma-treated PDMS surface showed a decrease of atomic content of carbon accompanied by an increase of oxygen content and suggests that the stiffening of PDMS surface can be attributed to generation of new cross-linking Si-O-Si and Si-CH2-CH2-Si bonds between PDMS molecules.