A copper strip just 6 micrometers thick sits between magnetic layers in a tiny device built at the University of Florida. The stripline microinductor, made with nickel and iron oxide nanoparticles, produced about 1.6 nanohenries of inductance—more than twice the amount measured in a similar device without a magnetic core.
Inductors help control the flow of power inside electronic circuits. In a switching voltage regulator, they briefly store energy in a magnetic field and help smooth out rapid changes in current. That steadier supply matters to computer chips, whose transistors need power at the right voltage. But shrinking an inductor can also reduce its inductance, making it harder to fit useful power-control hardware close to the circuits it serves.
The Florida team set out to add magnetic material in a form that could fit into a microfabricated device. The researchers combined iron oxide nanoparticles with nickel, using a process called electroinfiltration. They first placed the nanoparticles, then electrochemically grew nickel into the gaps between them. The result was a metal matrix with tiny magnetic particles embedded throughout it.
They built the composite into a stripline microinductor. An insulated copper conductor runs between magnetic layers above and below it. Those layers create a path for magnetic flux around the conductor, increasing the inductance it can provide. The researchers compared their device with an air-core version, which has no added magnetic core, and measured more than twice the inductance.
Making the layers fit together was a practical challenge. The insulation over the copper initially had steep sides, which made it difficult to form a continuous upper magnetic layer. The team softened and reshaped the photoresist—the material used to define parts of the device during fabrication—to give it a rounded profile. That allowed them to increase the copper thickness from about 2 to 6 micrometers while keeping the magnetic layer in place. The thicker copper also reduced winding resistance.
The work, conducted at the University of Florida by Sai Pranesh Amirisetti and coauthors Brenden M. Mears, Noah Morgan, Jennifer S. Andrew and David P. Arnold, was published in the Journal of Micromechanics and Microengineering. It joins materials science with the detailed work of building and testing small electrical structures.
The result is a demonstration, not a finished chip component ready for widespread use. The team’s measurements show that a magnetic nanocomposite can raise inductance in a compact, fabricated device, addressing one obstacle to shrinking power-management hardware. Higher switching frequencies can also help regulators use smaller inductors, but magnetic materials must respond quickly without losing too much energy. The study points to a route for placing magnetic materials inside small structures; further work will be needed to establish how the devices perform in practical chip power systems.