Creating 3D printed magnetic devices with ferrofluids and liquid metals

Abstract

Combining electrical and magnetic materials in the same part has been a challenge in 3D printing due to difficulties co-printing complex materials in many additive manufacturing processes. Past 3D printed inductors and other similar magnetic devices have therefore either lacked the magnetic materials necessary for improved performance, or required sintering at high temperatures for extended periods, beyond the capability of most 3D printable polymers. In this work, we demonstrate a room temperature process for incorporating conductive and magnetic materials into the same 3D printed device. A multi-stage fabrication process based on 3D printing followed by fill with magnetic and conductive fluids is proposed. Multi-layer microfluidic channels for magnetic passives are first printed in a stereolithography process. The microfluidic systems are then filled with room temperature liquid metal, a gallium alloy liquid at room temperature, and ferrofluid to create inductors, transformers and wireless power coils. Through the addition of ferrofluid as a magnetic material, increases in inductance density by nearly a factor of three were demonstrated, in addition to coupling improvements for transformer and wireless power coils compared to the devices before magnetic fill.