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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 30: Charged Soft Matter, Polyelectrolytes and Ionic Liquids II

CPP 30.2: Vortrag

Mittwoch, 20. März 2024, 15:15–15:30, H 0107

Ion dynamics and resonance in an electrical double layer undergoing periodic excitation by a surface acoustic wave — Sudeepthi Aremanda, Oles Dubrovsky, and •Ofer Manor — Technion - Israel Institute of Technology, Haifa, Israel

Electrical double layers (EDLs) appear at the interface between charged surfaces and electrolyte solutions and are one of the most fundamental and abundant mechanisms in nature. Steady and quasi-steady measurements of EDL properties are commonplace. However, the EDL Debye length, measured in nanometers, and the ion relaxation time through the Debye length, measured in nanoseconds, have made measurements of ion dynamics inside EDLs elusive.

We capture EDL dynamics by imposing a field effect, an evanescent mechanical wave generated in an electrolyte solution by a MHz-frequency surface acoustic wave (SAW) traveling in a neighboring substrate. Ions in the EDL undergo mechanical vibrations at the SAW frequency and support a same frequency leakage of alternating electrical field off the EDL that we measure. Moreover, a SAW excitation frequency comparable to the inverse of an ion relaxation time supports electro-mechanical ion resonance. The latter maximizes the ion mechanical vibration and the magnitude of the electrical field leakage, rendering ion-specific relaxation times measurable and giving the intrinsic rate of EDL charge and discharge by specific ions. [1]

[1] S. Aremanda and O. Manor, J. Phys. Chem. C, 2023, 127, 20911-20918

Keywords: electrical double layer; electrokinetics; surface acoustic wave; electrolytes; acoustics