The development of quartz crystal microbalance

Abstract

Quartz crystal microbalance (QCM), which is a sensitive and practical tool for measurement of the changes of interface, has got certain applications in the study of interface problems in physical, chemical, biological, pharmaceutical, clinical medicine and environmental science. However, the application and promotion of QCM in liquid phase has been limited by the difficulties of quantitative interpretation of QCM data. To solve this problem, researchers have developed a variety of advanced QCM, such as the QCM with the impedance analysis (impedance QCM, i-QCM) or the QCM that can monitor the energy dissipation (QCM with dissipation, QCM-D). At the same time, many corresponding theoretical models also have been developed. However, for most biological and chemical researchers, these theories are too complicated, which greatly limits the potential of QCM study. This review classified the reported methods, models and equations of QCM into five categories by application conditions with a clue of our groups research work in the QCM and provided a clear definition of criteria: i) solid-gas interface; ii) Newtonian fluid; iii) solid-liquid interface of thin film studies; iv) solid-liquid interface of thick film studies; v) solid-liquid interface of ultra-thick film studies. For each type of situation, we will describe how to simplify the QCM data and ensure the accuracy of quantitative analysis in simple language that chemists and biologist can understand. For QCM data analysis in liquid environment, we emphatically introduce the “solidified liquid” model, which allows QCM become a molecular ruler under certain conditions with the working range from nanometers to micrometers. The molecular ruler has a good application in some innovative interface researches. Finally, we theoretically analyze the defects of QCM as a biosensor -- the sensitivity of protein concentration detection is limited by the “detection of surface average mass” at only 1 μg mL^-1. Furthermore, we propose the development direction and potential applications of QCM, and hope that QCM can be extended in various problems of the interface application.