Investigating the Mass Sensitivity of Quartz Crystal Microbalances with Circularly Symmetric Electrodes in the Third Overtone Mode

This study investigates the mass sensitivity of a quartz crystal microbalance (QCM) with a circular symmetric electrode (M-M type) operating in the third overtone mode and finds that its central mass sensitivity is nearly five times greater than that of the fundamental mode, as determined through a deposition experiment, rather than the three times greater central mass sensitivity predicted by classical theory. The reasons for this phenomenon were determined through a combination of theoretical calculation and finite element simulation. The results revealed that (1) compared with the fundamental mode, the third overtone mode exhibits a more pronounced energy trapping effect, leading to a sharper mass sensitivity distribution and a more concentrated sensitivity in the central region and (2) the third overtone resonance frequency is slightly higher than three times the fundamental resonance frequency. This study indicates that operating the QCM in the third overtone mode significantly enhances its mass sensitivity, making it particularly suitable for applications requiring precise detection.