Leppin Christian, Hampel Sven, Meyer Frederick Sebastian, Langhoff Arne, Fittschen Ursula Elisabeth Adriane, Johannsmann Diethelm
Institute of Physical Chemistry, Clausthal University of Technology, Arnold-Sommerfeld-Str. 4, D-38678 Clausthal-Zellerfeld, Germany.
Institute of Inorganic and Analytical Chemistry, Clausthal University of Technology, Arnold-Sommerfeld-Str. 4, D-38678 Clausthal-Zellerfeld, Germany.
Sensors (Basel). 2020 Oct 20;20(20):5915. doi: 10.3390/s20205915.
A quartz crystal microbalance (QCM) is described, which simultaneously determines resonance frequency and bandwidth on four different overtones. The time resolution is 10 milliseconds. This fast, multi-overtone QCM is based on multi-frequency lockin amplification. Synchronous interrogation of overtones is needed, when the sample changes quickly and when information on the sample is to be extracted from the comparison between overtones. The application example is thermal inkjet-printing. At impact, the resonance frequencies change over a time shorter than 10 milliseconds. There is a further increase in the contact area, evidenced by an increasing common prefactor to the shifts in frequency, Δ, and half-bandwidth, ΔΓ. The ratio ΔΓ/(-Δ), which quantifies the energy dissipated per time and unit area, decreases with time. Often, there is a fast initial decrease, lasting for about 100 milliseconds, followed by a slower decrease, persisting over the entire drying time (a few seconds). Fitting the overtone dependence of Δ() and ΔΓ() with power laws, one finds power-law exponents of about 1/2, characteristic of semi-infinite Newtonian liquids. The power-law exponents corresponding to Δ() slightly increase with time. The decrease of ΔΓ/(-Δ) and the increase of the exponents are explained by evaporation and formation of a solid film at the resonator surface.
本文描述了一种石英晶体微天平（QCM），它能同时测定四种不同泛音的共振频率和带宽。时间分辨率为10毫秒。这种快速的多泛音QCM基于多频锁定放大技术。当样品变化迅速以及需要从泛音之间的比较中提取样品信息时，就需要对泛音进行同步询问。应用实例是热喷墨打印。在冲击时，共振频率在短于10毫秒的时间内发生变化。接触面积进一步增加，这可由频率偏移量Δ和半带宽ΔΓ的共同前置因子增加来证明。量化单位时间和单位面积耗散能量的ΔΓ/(-Δ)比值随时间降低。通常，最初会有一个快速下降，持续约100毫秒，随后是一个较慢的下降，贯穿整个干燥时间（几秒）。用幂律拟合Δ()和ΔΓ()的泛音依赖性，发现幂律指数约为1/2，这是半无限牛顿液体的特征。对应于Δ()的幂律指数随时间略有增加。ΔΓ/(-Δ)的降低和指数的增加是由谐振器表面的蒸发和固体薄膜的形成所解释的。
