Unconventional Protocol for SAW Sensor: Multi-Physic Response Enrichment in Liquid Medium

This paper presents a new paradigm in the analysis and methodology for Surface Acoustic Wave (SAW) devices for sensing application in a liquid medium. This new protocol encourages the analysis of the electrical and electro-acoustic behavior of the sensor rather than limiting the measurement interest to mechanical interactions between the sensor and the adjacent medium. This work focuses on a “holistic” approach, mainly seeking to achieve an improved understanding of the sensing phenomena and to enrich the global response and its analysis. Even though this work does not aim to enhance the general sensitivity, it could be used to improve the design of the sensor for a specific target. Our methodology is based on the separation of electrical and mechanical mechanisms with post-treatment analysis of experimental responses, using jointly frequency and time domains analysis. It is supported by an unconventional energy flow chart of the acoustic wave propagation in the SAW device which helped us extracting a few hypotheses. This new paradigm allows us to get information related to both dielectric and mechanical parameters of a liquid sample using a single sensor, thus enriching the response at no cost. In this paper, we applied the method to Love wave sensors with different technological characteristics influencing the electric and acoustic response, and numerous fluid solutions for a large diversity of dielectric constants and mechanical properties. The large set of measurement allows the extraction of both dielectric and mechanical parameters of a liquid medium on the Love wave sensor surface.