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Functional brain imaging has tremendous applications. The existing methods for functional brain imaging include functional Magnetic Resonant Imaging (fMRI), scalp electroencephalography (EEG), implanted EEG, magnetoencephalography (MEG) and Positron Emission Tomography (PET), which have been widely and successfully applied to various brain imaging studies. To develop a new method for functional brain imaging, here we show that the dielectric at a brain functional site has a dynamic nature, varying with local neuronal activation as the permittivity of the dielectric varies with the ion concentration of the extracellular fluid surrounding neurons in activation. Therefore, the neuronal activation can be sensed by a radiofrequency (RF) electromagnetic (EM) wave propagating through the site as the phase change of the EM wave varies with the permittivity. Such a dynamic nature of the dielectric at a brain functional site provides the basis for an RF EM wave approach to detecting and imaging neuronal activation at brain functional sites, leading to an RF EM wave approach to functional brain imaging.

The effect of the magnetic field on the magnetic properties of NiFe/Cu composite wires electroplated under a longitudinal magnetic controlling field is presented. Composite wire samples of 20-μm-diameter Cu electroplated with a layer of Permalloy™ (Ni80Fe20) under the influence of a longitudinal magnetic field of intensities ranging from 0 to 400 Oe were produced, and the microstructure and magnetic properties were measured. The results showed that the longitudinal magnetic field in the composite wire plating makes the packing of the crystals in the plated layer more orderly, and thus increases the uniformity and magnetic softness of the plated material. It also shifts the magnetic anisotropy of the plated layer from circumferential to longitudinal, and increases the critical frequency of the plated composite wire in magnetoimpedance effect testing, at which the magnetoimpedance ratio reaches the maximum.

In this study, for developing microsensors for weak magnetic field, methods for developing high permeability nanocrystalline permalloy by electrodeposition and the relationship between the grain size and magnetic properties of the nanocrystalline permalloy are investigated. By dc plating with and without saccharin added and pulse plating with saccharin added, permalloy samples of grain sizes from 52 nm to 11 nm are obtained. The coercivity and magnetoimpedance (MI) ratio of the samples are tested against the grain size variation. Results show that the coercivity decreases rapidly and MI ratio increases greatly with grain size decrease from 52 nm to 11 nm.