Abstract :
The paper describes a wet process for modifying the surface of polydimethylsiloxane (PDMS) using H2SO4/HNO3 solutions. The oxidation on
the surface of PDMS was confirmed by the examinations of Fourier transform infrared spectrometry (FTIR), contact angle of water drop and X-ray
photoelectron spectroscopy (XPS). The hydrophobic surface of pristine PDMS was not only changed to hydrophilic, but also formed wrinkles on it
after chemical modification. Bilayer systems, stiff oxidized PDMS layers were capped on soft PDMS foundations, would generate easily
compressive stresses due to the large difference in volumetric contraction rates and led to form wrinkles on the surface. Experimental results
demonstrated the periodicity of wrinkles was controllable by controlling the duration of oxidation. Therefore, wrinkles could be arranged orderly
by the guidance of external forces before oxidization. The potential technology for generating and ordering wrinkles on the PDMS surface is
valuable in the applications of pressure sensors, biology, micro-optics and nano-/micro-fabrication in the future
