An Improved F/C Structure for Cell-Scale Micro-Magnetic Coil

Cell-scale micro-magnetic stimulation is the process of stimulating neuronal tissues using a sub-millimeter coil. During the process, a time-varying current is fed to the micro-coil, and the micro-coil generates a dispersed magnetic field in the focal region of the tissue to create the effect of magnetic stimulation. The micro-magnetic coil has the drawbacks of small inductance, large power consumption, low-quality factor, and uneven distribution of magnetic induction. In this article, we designed an improved F/C structure, which was surrounded by a magnetic film/planar coil, and developed a method for determining the geometric parameters of the structure based on an investigation of how the pattern, thickness, spacing, and width of the magnetic shielding layer (MSL) affect the micro-coil inductance
$L$
and the magnetic induction
$B$
. The experimental results show: when the magnetic permeability
$\mu _{r}$
of the micro-magnetic coil with the improved F/C structure is 10
⁶
H/m, the inductance reaches 1149.3 nH, the maximum value of magnetic induction
$B$
on the
$Z = 800$
nm tangential surface reaches 11.33 mT, and the average value of
$B$
is 5.5 mT (the
$B$
value exceeds 4.28 mT in 92.6% of the area of the
$100\,\,\mu \text{m}\,\,\times 100\,\,\mu \text{m}$
micro-coil); the range of action of magnetic induction is approximately
$20~\mu \text{m}$
in the
$Z$
-direction. It can be concluded that the micro-magnetic coil with the improved F/C structure is superior to the existing micro-coils in terms of magnetic field uniformity, action strength, and inductance value, and the increased inductance value improves the quality factor
$Q$
of the coil and reduces the power consumption of the micro-magnetic coil.