Oscillating frequency response of a langasite crystal microbalance in liquid phases

Langasite (La3Ga5SiO14) crystal is one of the perspective crystalline materials for various applications in acoustoelectron and piezoelectric devices. In this work, the frequency responses of resonators made from Y-cut langasite crystal in a liquid phase were investigated. It was shown that the oscillating frequency of the langasite resonator decreased with increasing the surface mass loading, viscosity (η) and density (ρ) of the liquid phase. The correlation of the frequency shift and the mass loading was similar to the Sauerbrey equation. A linear dependence of the frequency shift on the surface mass loading was obtained within 3% of the intrinsic frequency of the langasite resonator. The frequency–mass coefficient of the langasite crystal microbalance (LCM) was 71.7% of that of the classical quartz crystal microbalance (QCM). The frequency of the LCM decreased linearly with increasing (ρη)1/2 The LCM had a low frequency–temperature coefficient in water in the temperature range of 30–50 °C. The LCM possessed excellent oscillating ability in the oscillator method, especially in high viscosity liquids. It could be operated in pure glycerol with two faces in contact with the liquid phase. The LCM was applied to monitor the coagulation process of whole blood.