Plasma surface modification of hydrogel thin films

During sensor fabrication, hydrogel thin films of poly(vinylalcohol)/poly(acrylic acid) (PVA/PAA) is exposed to various low pressure plasmas. To conserve the sensing properties of the hydrogel, a precise knowledge of the interaction of the PAA/PVA film with the low-pressure plasmas of the technological cycle is required. In this work, an investigation of the film surface composition, chemical bonding and optical properties of radio-frequency (13.56 MHz) and dual-frequency (13.56 MHz/100 kHz) plasma modified PAA/PVA thin films were carried out. Plasma treatment was performed in a RIE chamber (SF6, CHF3) and a PECVD deposition chamber (SiH4/N2, NH3). To investigate the influence of ion bombardment, a dual-frequency configuration comprising two r.f. power supplies operating in a switched mode was used. The results of this work allow optimizing the fabrication of thin film pH-value sensors.