Acoustic wave resonators have become suitable devices for a broad range of sensing applications due to their sensitivity, low cost, and integration capability, which are all factors that meet the requirements for the resonators to be used as sensing elements for portable point of care (PoC) platforms. In this work, the design, characterization, and validation of a 150 MHz high fundamental frequency quartz crystal microbalance (HFF-QCM) sensor for bio-sensing applications are introduced. Finite element method (FEM) simulations of the proposed design are in good agreement with the electrical characterization of the manufactured resonators. The sensor is also validated for bio-sensing applications. For this purpose, a specific sensor cell was designed and manufactured that addresses the critical requirements associated with this type of sensor and application. Due to the small sensing area and the sensor’s fragility, these requirements include a low-volume flow chamber in the nanoliter range, and a system approach that provides the appropriate pressure control for assuring liquid confinement while maintaining the integrity of the sensor with a good base line stability and easy sensor replacement. The sensor characteristics make it suitable for consideration as the elemental part of a sensor matrix in a multichannel platform for point of care applications.

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AT-cut quartz crystals have been driven with the so-called lateral field excitation. When applying a voltage to the two electrodes placed on one crystal surface and separated by a small gap an electric field is generated, which is mainly confined in the lateral direction. Extraordinary changes can be observed in the conductance spectrum when applying a liquid to the other (bare) surface of the crystal. In contrast to traditional quartz crystal sensors, these changes must be attributed to electrical properties of the adjacent medium. It is suggested that a redistribution of the exciting electric field from the lateral toward the thickness direction occurs. The assumption is supported by simulations which allow insights into the piezoelectric excitation and transduction mechanism of the acoustic device under varied electrical boundary conditions at the bare surface as well as the shear displacement patterns involved. Results from 10 MHz plano–plano and 6 MHz plano–convex sensors which have been exposed to liquids of varying permittivity show the strong dependence of the sensor response on liquid permittivity which overlies the known dependence on density–viscosity.

Miniaturized, high-throughput, cost-effective sensing devices are needed to advance lab-on-a-chip technologies for healthcare, security, environmental monitoring, food safety, and research application. Quartz crystal microbalance with dissipation (QCMD) is a promising technology for the design of such sensing devices, but its applications have been limited, until now, by low throughput and significant costs. In this work, we present the design and characterization of 24-element monolithic QCMD arrays for high-throughput and low-volume sensing applications in liquid. Physical properties such as geometry and roughness, and electrical properties such as resonance frequency, quality factor, spurious mode suppression, and interactions between array elements (crosstalk), are investigated in detail. In particular, we show that the scattering parameter, S21, commonly measured experimentally to investigate crosstalk, contains contributions from the parasitic grounding effects associated with the acquisition circuitry. Finite element method simulations do not take grounding effects into account explicitly. However, these effects can be effectively modelled with appropriate equivalent circuit models, providing clear physical interpretation of the different contributions. We show that our array design avoids unwanted interactions between elements and discuss in detail aspects of measuring these interactions that are often-overlooked.

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