Design and Optimization of Resonance-Based Wireless Power Transmission for Millimeter-sized Planar Square Inductors Micro-magnetic Stimulation

In this article, a wireless passive micro-magnetic stimulation (WP-μMS) for isolated hippocampal slices is designed. Wireless power transmission (WPT) is used to couple the energy from the transmitting coil into the micro-coil to achieve magnetic stimulation for the cell. However, the critical issue involved here is to improve the signal-to-noise ratio (SNR) of the micro-coil stimulation target and reach the threshold of effective magnetic stimulation. First, the magnetic coupling resonance WPT theory and finite element analysis model of the WP-μMS are established. The transmission efficiency and mutual inductance of the WP-μMS are measured at different resonant frequencies. Second, the magnetic field strength and magnetic field distribution regularity of the stimulated targets in hippocampal brain slices are analyzed. The system achieves a WPT efficiency of 39.58% at a resonance frequency of 920 kHz with a guaranteed threshold of 1 mT effective magnetic field strength generated by the micro-coil. Last, biological experiments based on isolated hippocampal brain slices are performed for validation. The results show that the WP-μMS enhances the synaptic plasticity long-term potentiation (LTP) in the hippocampal CA1 region.