EFFECT OF UV RADIATION DURATION AND MOLECULAR WEIGHT TO HYDROPHOBICITY AND SURFACE ROUGHNESS OF POLYSTYRENE COATING ON QCM SENSOR

Abstract

Hydrophobicity is one of important solid surface properties for the development of Quartz Crystal Microbalance (QCM) biosensor. Hydrophobicity plays a role in the biomolecule immobilisation. Polystyrene is one of the coating materials used in the QCM biosensor, where the sensitive biomolecule material is immobilised. Hydrophobicity and surface roughness can be controlled by many methods. In this work, we investigated the effect of the polymer molecular weight and UV radiation on the surface roughness and hydrophobicity. The polystyrene with a molecular weight of 35,000 g/mol, 192,000 g/mol, and 280.000 g/mol were solved in toluene with a concentration of 3%, 5%, and 7% and coated using spin coating method on top of the QCM sensor. The coated polystyrene on QCM sensor was irradiated using UV lamp with a wavelength of 254 nm. The contact angle of water before and after UV irradiated was measured using contact angle instrument and the surface roughness is measured using non-contact optical profilometer. The result shows that the higher molecular weight of polystyrene led to more hydrophobic surface. Radiation under UV light increases the hydrophobicity of polystyrene surface. The surface roughness of the polystyrene on top of the sensor is not affected by UV irradiation.