Surface modification and wettability of silicone PDMS film

In this work, silicone PDMS (polydimethylsiloxane) films were deposited on 100 mm silicon wafer by spin-coating technique and its surface is modified by plasma CHF₃ and O₂ treatment in a vacuum chamber, respectively. Wettable surface is obtained through subsequent plasma O₂ treatment. Scanning Electron Microscope (SEM) and Energy dispersive x-ray spectroscopy (EDX) indicate that the plasma CHF₃ treatment induces the formation of island-like nano-structures. The chemical composition of the island-like nano-structures is silicon-rich in near surface region. The surface roughness increases from 9 nm to 230 nm as plasma treatment time increases from 0 to 40 minutes. The wettability of the PDMS surface is strongly dependent on its roughness and the time of plasma O₂ treatment. A typical contact angle of 5 μL water droplet after aging 25 hours at room temperature is about 35 ° on the PDMS surface with roughness 230 nm.