Oxygen plasma treatment of sputtered TiO2 thin film for surface modification of PDMS

We present the modification of polydimethylsiloxane (PDMS) surface by titanium dioxide (TiO
₂
) thin film coating and subsequent oxygen plasma treatment. TiO
₂
thin film was deposited on the prepared PDMS samples by reactive dc sputtering. Pure Ti target was sputtered under a mixture of argon and oxygen plasma, in which the argon to oxygen flow rate ratio is 1:4. Finally, TiO
₂
coated PDMS structures were treated by O
₂
plasma at a low plasma power of 6.8 Watt with different treatment times. The micro crack of TiO
₂
thin film observed by optical microscope was found to be uniformly distributed on the PDMS surface. The crystal structure of TiO
₂
investigated by X-ray diffraction (XRD) confirms that the structure TiO
₂
thin film on PDMS is amorphous. To characterize the hydrophilic property, the contact angle of PDMS and TiO
₂
coated PDMS were measured as a function of oxygen plasma treatment time. It was found that the contact angle of treated PDMS is dropped from 117 to 9 degrees after oxygen plasma treatment for 1 minute. While the contact angle of TiO
₂
coated PDMS is sharply dropped from 88 to 7.8 degrees after oxygen plasma treatment for 1 minute. Therefore, the improvement of hydrophilicity surface properties of PDMS is successfully obtained by TiO
₂
thin film coating and subsequent oxygen plasma treatment.