It Really a Microbalance

Is the quartz crystal microbalance really a microbalance For one thing, it should rightly be called a nano-balance, considering that the sensitivity of modern-day devices is on the order of 12 ng/cm and could be pushed further, if necessary. More importantly, calling it a balance implies that the Sauerbrey equation applies strictly, namely that the frequency shift is the sole result of mass loading. It is well known that this is not the case, and the frequency shift observed could more appropriately be expressed by a sum of terms of the form 

It should be evident from the above arguments that the term quartz crystal microbalance is a misnomer, which could (and indeed has) lead to erroneous interpretation of the results obtained by this useful device. It would be helpful to rename it the quartz crystal sensor (QCS), which describes what it really does—it is a sensor that responds to its nearest environment on the nano-scale. However, it may be too late to change the widely used name. The QCM or its analogue in electrochemistry, the EQCM, can each act as a nano-balance under specific conditions, but not in general. 

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