This study presents an AlN based Lamb wave (A0 mode) liquid sensing device that can be used for biomedical applications. The Lamb wave device features a 1.5 μm composite membrane consisting of a 500 nm LPCVD SiN and a 1 μm of a c-axis oriented AlN film. A 45° rotated design was also considered for this project to reduce the reflections from the edges towards the output IDT. A liquid testing experiment involving IPA, DI water, and D-PBS was performed to see if the devices were able to differentiate between these liquids. The results showed that the fabricated Lamb wave devices exhibited sensitivity to mass loading and were able to distinguish between the liquids based on their phase, frequency, and gain characteristics. Notably, devices with the rotated design have shown a substantial increase in resonance by 15 dB, as well as enhanced sensitivity, when compared to the devices with the normal design. Furthermore, the devices featuring the normal design had a Q factor of 450, whereas devices with the rotated design exhibited a Q factor of 680, indicating superior performance of the latter. These findings suggest that a Lamb wave device with the 45° rotated IDT design holds considerable potential for liquid sensing, particularly in biomedical applications.

This review offers a detailed examination of the current landscape of radio frequency (RF) electromagnetic field (EMF) assessment tools, ranging from spectrum analyzers and broadband field meters to area monitors and custom-built devices. The discussion encompasses both standardized and non-standardized measurement protocols, shedding light on the various methods employed in this domain. Furthermore, the review highlights the prevalent use of mobile apps for characterizing 5G NR radio network data. A growing need for low-cost measurement devices is observed, commonly referred to as “sensors” or “sensor nodes”, that are capable of enduring diverse environmental conditions. These sensors play a crucial role in both microenvironmental surveys and individual exposures, enabling stationary, mobile, and personal exposure assessments based on body-worn sensors, across wider geographical areas. This review revealed a notable need for cost-effective and long-lasting sensors, whether for individual exposure assessments, mobile (vehicle-integrated) measurements, or incorporation into distributed sensor networks. However, there is a lack of comprehensive information on existing custom-developed RF-EMF measurement tools, especially in terms of measuring uncertainty. Additionally, there is a need for real-time, fast-sampling solutions to understand the highly irregular temporal variations EMF distribution in next-generation networks. Given the diversity of tools and methods, a comprehensive comparison is crucial to determine the necessary statistical tools for aggregating the available measurement data.