Characterizing piezoelectric materials under mechanical stress in liquid media: An electrokinetic approach

Abstract

Piezoelectric materials are an integral part of the modern world, as they find wide-ranging applications in various advanced domains such as telecommunications, automotive, electronics, and aerospace. Recently, these materials gained interest also for applications in liquid environments across diverse fields, including biomedical engineering, purification systems, electrocatalysis, fluid characterizations and micro/nano electromechanical systems (MEMS/NEMS). Despite their growing importance, many questions remain unanswered regarding their characterization and the evaluation of their performance in liquid media. It is critical to understand how these materials interact with surrounding ionic species under mechanical stress application. To address these questions, a novel experimental setup has been designed to characterize piezoelectric materials through electrokinetic measurements in a liquid environment. A polarized piezoelectric sample (lead zirconate titanate) is subjected to a mechanical stress, which is known to influence the piezoelectric surface charge state. This change in surface charge state can be monitored through measurement of the streaming potential. The results indicate that there is a strong correlation between the applied mechanical stress and the electrokinetic response of the piezoelectric sample. When the sample is subjected to a dynamic stress variation, its electrokinetic response closely follows the profile of the applied stress. In addition, the stress applied to the piezoelectric sample directly impacts the flow cell’s resistance. A non-piezoelectric material (alumina) is also subjected to similar stress conditions. Both electrokinetics and resistance of the flow cell remain almost unchanged for the non-piezoelectric alumina sample during the stress application. Finite element modeling is employed to model variation of surface charge on the piezoelectric sample due to stress application. The piezoelectric model is then coupled with electrokinetic and resistance models to explore the effect of stress on the electrical responses of the system. The modeling results exhibit high degree of consistency with the experimental observations.