As electronics get smaller and smaller – and use more and more components – microchip development is in a never-ending battle for minimization. Now, researchers at the University of Illinois have developed a new inductor fabrication technique that could use up to a hundred times less chip space.

Typical microchip inductors are 2D wire spirals and occupy a significant portion of microchips. But recently, a team of researchers led by Xiuling Li (interim director of the Holonyak Micro and Nanotechnology Laboratory and an electrical and computer engineering professor at the University of Illinois) managed to create a 3D inductor that could still fit on a microchip.

To do this, they switched to a “rolled membrane paradigm,” which let them spiral the wires on top of each other (with a thin insulating film between layers), creating a self-rolling, magnetic, nano-particle filled tube. A previous iteration of this research managed to create rolled inductors with a wire length of 1 mm, but the researchers have announced that a new tweak to the process allows wire lengths of 1 cm, increasing the spatial efficiency even further.

“A longer membrane means more unruly rolling if not controlled,” Li said. “Previously, the self-rolling process was triggered and took place in a liquid solution. However, we found that while working with longer membranes, allowing the process to occur in a vapor phase gave us much better control to form tighter, more even rolls.”

The researchers also sought to add a solid iron core, which, Li explained, is a characteristic feature of the most efficient inductors. “But that does not work at the microchip level,” she said, “nor is it conducive to the self-rolling process, so we needed to find a different way.” So instead of wrapping the wire around an iron core, the researchers reversed the process: they filled the rolled wire with an iron oxide solution.

“We take advantage of capillary pressure, which sucks droplets of the solution into the cores,” Li said. “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.”

Of course, there are still challenges to address.

“As with any miniaturized electronic device, the grand challenge is heat dissipation,” she said. “We 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.”

Header image: some of the new inductors mid-roll. Image courtesy of the University of Illinois.

To read the University of Illinois’ article discussing this research, click here.