Magneto-acousto-electric effects based on focused acoustic-vortex beams in a coaxial magnetic field.

As an innovative neural modulation technique, the transcranial magneto-acousto-electric (MAE) stimulation (TMAES) realizes the synergistic regulation of neuronal discharge through the ultrasonic mechanical and inductive electric effects, offering significant prospects in biomedical applications. However, the stimulation accuracy is still limited by the unidirectional distribution of MAE field intensity. A method of constructing center-converging MAE field by coupling the helical wave fronts of focused acoustic-vortex (FAV) beams with a coaxial magnetic field is proposed. By describing FAVs with Laguerre–Gaussian functions, the theory of MAE field construction is derived in explicit formulae and the spatiotemporal characteristics of MAE fields in the focal region are analyzed. It is theoretically and experimentally demonstrated that the MAE field generated by the FAV of lth order is determined by those of (l − 1)th and (l + 1)th orders. The center-converging phase-rotating MAE field can only be generated by the FAV of first order, maintaining a constant peak intensity at the vortex center. Experimental distributions of MAE fields for FAVs of different orders show good agreements with numerical simulations. With the peak pressure of 0.86 MPa and the magnetic intensity of 0.3 T, the peak intensity of 62.1 mV/m reaching the electric stimulation threshold is achieved. The center-converging MAE field constructed by FAV may develop a new synergistic neural modulation scheme for TMAES with enhanced precision and flexibility while ensuring safety and efficacy, thereby exhibiting significant scientific and practical implications. [ABSTRACT FROM AUTHOR]