Design And Research Of Cell-level Micro-magnetic Stimulation Coil Based On MEMS Structur

Micro-magnetic stimulation(μMS)is a novel neuromodulation technique that can realize targeted modulation of neural activity in the brain.It has the advantages of small size and high spatial resolution.Currently,μMS primarily use commercial micro inductors,but their single structure limits the functionality of magnetic stimulation.Therefore,a cell-level micro-magnetic stimulation coil based on MEMS(MicroElectro-Mechanical System)structure is proposed in this paper.The primary critical work accomplished is the theoretical analysis,MEMS process design,and biological experiments.The main contents are as follows:Firstly,an improved F/C(Film/Coil)structure micro magnetic stimulation coil with an additional cap structure magnetic shielding layer was designed.The magnetic layer pattern,the spacing between the magnetic layer and the micro-coil,and the thickness and width of the magnetic layer were optimized.The MEMS structure and processing of this micro coil were investigated.The inductance improved compared to the existing MEMS structure with a single coil.Secondly,a new MEMS structured 4×4 array micro-magnetic stimulation coil was developed.The spatial distribution of the electromagnetic field in the arraystructured micro coil was investigated when multidirectional currents were applied.An algorithm for predicting the area of focus of the electromagnetic field of a 4×4 array structured micromagnetic stimulator is presented.It enables the selection of a directional movement of the stimulation target and improves the focus and effectiveness of magnetic stimulation.Thirdly,a measurement device for millimeter-sized planar square spiral coils was designed for magnetic field strength.A theoretical model of mutual inductance was developed for different locations and sizes.The physical model was constructed using finite element analysis to verify the correctness of the mutual inductance model.Experimental results showed that the device enables the measurement of highfrequency weak magnetic fields in millimeter-sized micro-coils.The challenge of accurate dose control of magnetic field strength for micromagnetic stimulation is solved.Fourthly,a cell-level passive micromagnetic stimulator for isolated hippocampal brain slices was invented.The magnetic coupling resonance wireless power transmission(WPT)theory and finite element analysis model were established.The magnetic field intensity distribution pattern at the stimulation target of hippocampal brain slices was investigated.Bio-experimental validation of the micro-magnetic stimulator was performed on isolated hippocampal brain slices.The experimental results showed that the cell-level passive micromagnetic stimulator enhanced synaptic plasticity long-term potentiation(LTP)in the hippocampal CA1 region.The accuracy of micro-coil localization in the CA1 region of the hippocampal slice was improved.