Image of microinductor architecture
A scanning electron microscope micrograph of a rolled microinductor architecture, approximately 80 micrometers in diameter and viewed from one end looking inward. (Reprinted with permission from X. Li et al., Science Advances 2020).

A team of engineers at University of Illinois at Urbana-Champaign has boosted the performance of its previously developed 3D inductor technology by adding as much as three orders of magnitudes more induction to meet the performance demands of modern electronic devices. The microchip inductor is capable of tens of millitesla-level magnetic induction. Using fully integrated, self-rolling magnetic nanoparticle-filled tubes, the technology ensures a condensed magnetic field distribution and energy storage in 3D space — all while keeping the tiny footprint needed to fit on a chip.

Traditional microchip inductors are relatively large 2D spirals of wire, with each turn of the wire producing stronger inductance. The research group developed 3D inductors using 2D processing by switching to a rolled membrane paradigm, which allows for wire spiraling out of plane and is separated by an insulating thin film from turn to turn. When unrolled, the previous wire membranes were 1 millimeter long but took up 100 times less space than the traditional 2D inductors. The wire membranes are 10 times the length, at 1 centimeter, allowing for even more turns — and higher inductance — while taking up about the same amount of chip space.

Another key development in the new microchip inductors is the addition of a solid iron core. That was achieved by taking advantage of capillary pressure, which sucks droplets of the solution into the cores. The solution dries, leaving iron deposited inside the tube. This adds properties that are favorable compared to industry-standard solid cores, allowing these devices to operate at higher frequency with less performance loss.

As with any miniaturized electronic device, however, the grand challenge is heat dissipation. The engineers are addressing this by working with collaborators to find materials that are better at dissipating the heat generated during induction. If properly addressed, the magnetic induction of these devices could be as large as hundreds to thousands of millitesla, making them useful in a wide range of applications including power electronics, magnetic resonance imaging, and communications.

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