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

We present the modification of polydimethylsiloxane (PDMS) surface by titanium dioxide (TiO2) thin film coating and subsequent oxygen plasma treatment. TiO2 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, TiO2 coated PDMS structures were treated by O2 plasma at a low plasma power of 6.8 Watt with different treatment times. The micro crack of TiO2 thin film observed by optical microscope was found to be uniformly distributed on the PDMS surface. The crystal structure of TiO2 investigated by X-ray diffraction (XRD) confirms that the structure TiO2 thin film on PDMS is amorphous. To characterize the hydrophilic property, the contact angle of PDMS and TiO2 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 TiO2 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 TiO2 thin film coating and subsequent oxygen plasma treatment.