A novel quartz crystal resonator (QCR) sensor with a printed-on-crystal conductive coil, named sensor coil, is presented. The sensor coil electromagnetically coupled to an external readout coil allow to perform contactless interrogation of the QCR working as a stand-alone sensor unit. A frequency-domain readout technique is adopted that allows dual-harmonic operation by detecting the QCR frequencies of the fundamental and third harmonic, and offers first-order independence from the stand-off distance between the sensor and the readout unit. The QCR electrodes and sensor coil have been printed on a 330- ${\mu }\text{m}$ -thick bare AT-cut quartz crystal exploiting the aerosol jet printing technology. The fabricated QCR sensor has reference values of the fundamental and third harmonic frequencies at 4.77 and 14.22 MHz, respectively. Distance-independent contactless operation has been demonstrated for distances up to 12 mm. The readout frequencies deviate from reference values less than 10 and 90 ppm for the fundamental and third harmonic, respectively, thus validating the proposed principle.

中文翻译：

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石英晶体谐振器，带有印制在晶体上的线圈，用于双谐波电磁非接触式询问。

提出了一种新型的石英晶体谐振器（QCR）传感器，该传感器带有一个印在晶体上的导电线圈，称为传感器线圈。电磁耦合到外部读出线圈的传感器线圈允许执行作为独立传感器单元的QCR的非接触式询问。采用了一种频域读出技术，该技术可通过检测基波和三次谐波的QCR频率来实现双谐波操作，并提供与传感器和读出单元之间的隔离距离的一阶独立性。QCR电极和传感器线圈已印刷在330- $ {\ mu} \ text {m} $ 利用气溶胶喷射印刷技术的超薄裸露AT切割石英晶体。所制造的QCR传感器分别具有4.77 MHz和14.22 MHz的基波和三次谐波频率的参考值。距离无关的非接触式操作已被证明适用于最大12 mm的距离。对于基波和三次谐波，读出频率分别偏离小于10 ppm和90 ppm的参考值，从而验证了所提出的原理。