Abstract

The interfacial slip parameter is a complex-valued property of the interface between the solid surface of a quartz sensor and the liquid in contact with the sensor surface. It is introduced in the theory of the quartz-liquid system by generalizing the no-slip boundary condition. The interfacial slip parameter is defined as the displacement of a particle of liquid in contact with the sensor surface divided by the displacement of a particle on the surface of the sensor. The theoretical expression for impedance of the sensor is derived in terms of the interfacial slip parameter. The impedance of the sensor is measured by the network analysis method for hydrophilic and hydrophobic surfaces in water-glycerol solutions. The experimental values of impedance are fitted to the theory by non-linear regression analysis to find the interfacial slip parameter. A mechanical model of interfacial slip is devised which explains the variation of the interfacial slip parameter with viscosity of the liquid. The results indicate that there is considerable slip in low-viscosity liquids, near the viscosity of water, and very little slip in liquids of high viscosity, near that of glycerol.