Remote Focused Encoding and Decoding of Electric Fields through Acoustoelectric Heterodyning

Jean L. Rintoul, Esra Neufeld, Chris Butler, Robin O. Cleveland, and Nir Grossman, Nature Communications Physics 2023, Volume 6, Article No. 79, online 20 April 2023; doi: https://doi.org/10.1038/s42005-023-01198-w

Although heterodyning of signals through physical multiplication is the building block of numerous modern technologies, it has so far been limited mostly to interactions between electromagnetic fields (EMF). Here, we report that heterodyning occurs also between acoustic and electric fields in liquid electrolytes. We used computational field modeling, which accounts for the vector nature of the electrolytic acoustoelectric interaction to predict acoustoelectric heterodyning. We then experimentally validated the spatiotemporal characteristics of the fields emerging from the acoustoelectric heterodyning effect. The electric field distribution generated by the applied fields can be controlled by the propagating acoustic field and the orientation of the applied electric field, enabling the resulting electric field to be focused at remote locations. Finally, we demonstrated detection of multi-frequency ionic currents at a distant focal location via signal demodulation using pressure waves in electrolytic liquids. As such, acoustoelectric heterodyning could open possibilities for non-invasive biomedical and bioelectronics applications.

The scientific and technical impact of the study can be summarized as:

• The acoustoelectric effect can be exploited to remotely generate and manipulate highly localized EMF within ionic solutions or living tissue and to perform non-linear operations
• A newly developed vectorial theory of the acoustoelectric effect and hybrid electromagneto-acoustic simulations forms the basis for our findings
• The validity of the new theory, as well as the practical feasibility of the approach, was experimentally demonstrated by implementation of remote heterodyning in a tissue-like liquid medium
• The results open up exciting possibilities for applications ranging from non-invasive bioelectronics, to highly focused temporal interference brain stimulation and electric lensing