A New Synthesis Method for Complex Electric Field Patterning using a Multichannel Dense Array System with Applications in Low-Intensity Noninvasive Neuromodulation
Multichannel coil array systems offer precise spatiotemporal electronic steering and patterning of electric and magnetic fields without the physical movement of coils or magnets. This capability could potentially benefit a wide range of biomagnetic applications such as low-intensity noninvasive neuromodulation or magnetic drug delivery. In this regard, the objective of this work is to develop a unique synthesis method, that enabled by a multichannel dense array system, generates complex current pattern distributions not previously reported in the literature. Simulations and experimental results verify that highly curved or irregular (e.g., zig - zag) patterns at singular and multiple sites can be efficiently formed using this method. The synthesis method is composed of three primary components; a pixel cell (basic unit of pattern formation), a template array (“virtual array”: code that disseminates the coil current weights to the “physical” dense array), and a hexagonal coordinate system. Additionally, we demonstrate that the depth of penetration of the magnetic field can be controlled by varying coil current weights (magnitude and phase, 0 and π) of the smaller coil diameters in the array to achieve the same decay profile performance of a larger diameter coil. Only simulations exist in the literature to date, to the best of our knowledge, we report the first measurements of hexagonal shaped coils in multi-coil arrays have increased depth of penetration over circular shaped coil-based arrays. Finally, a method for localizing or reducing extraneous excitation around a user-defined E-field pattern is proposed and simulated. Low Intensity or Low-Field Magnetic Stimulation is identified as a potential application that could benefit from this work in the future and as such is used as an example to frame the research.