Increasing the selectivity of QCM sensors

10. 12. 2014

A team of scientists from the BUT Faculty of Electrical Engineering and Communication Technologies focused on improving the method of finding the presence of other substances in a gaseous environment, which is used e.g. in a range of industrial branches, military technology, toxicology, pharmaceutical technology, food industry, etc.

In detecting the presence of biological and/or chemical substances in a gaseous environment a piezoelectric sensor is used (a quartz crystal provided with a layer of substances absorbing gas molecules and a surface-absorbing molecule of other substances from the surrounding gaseous environment). Such a sensor (QCM – Quartz Crystal Microbalance – the same name is used for the overall measuring method) registers the deposition of extraneous substances on its surface via a change of weight and reacts to this by a change of its resonance frequency. The change is monitored and results of the measurement are obtained through an analysis of the measured data.

However, a certain problem with this procedure lies in physical effects in volume and on the surface of the active layer of the sensor, due to which the measured frequency fluctuates. Molecules of different substances may cause the same response of this mass sensor, i.e. increase the weight of the active layer to the same degree or with a non-discernible deviation and thus cause the same change of resonance frequency. In such a case, these substances cannot be distinguished unambiguously based on the standard measurement.

The principle of this innovative procedure developed by the BUT scientists (Prof. RNDr. Ing. Josef Šikula, DrSc., Doc. Ing. Vlasta Sedláková, Ph.D., Ing. Petr Sedlák, Ph.D., and Ing. Jiří Majzner, Ph.D., all from the BUT Faculty of Electrical Engineering and Communication Technologies) is extending the monitored parameters and fluctuations of the resonance frequency. The discovered values are then used for deriving the mean time of capturing the gas molecules on the sensor surface, and this data will enable the differentiation of gaseous substances which otherwise cause the same frequency deviation (detected by the classical measuring method). Therefore, the result of the new procedure is a significantly more precise identification of biological or chemical substances present in a gaseous environment than from identification enabled by current procedures and equipment.

With support from the Technology Transfer Office of BUT, the above-mentioned procedure was granted patent protection. Details are available here.

Source of the picture: archives of the Patent authors

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