Development of a Three-Axis Planar Hall Magnetoresistance Sensor Using a Superparamagnetic Nanoparticle-Based Flux Guide

Abstract

Accurate perception of 3D magnetic fields is essential for advanced spatial awareness in motion tracking and robotics. However, conventional magnetoresistance sensors typically lack out-of-plane sensitivity. Magnetic flux guides have been employed to redirect out-of-plane fields into the sensor plane, yet ferromagnetic flux guides introduce unwanted hysteresis, necessitating complex reset mechanisms that hinder miniaturization. Here, we present a highly sensitive 3D planar Hall magnetoresistance (PHMR) sensor integrated with a superparamagnetic nanoparticle-based flux guide (SPMFG). Crucially, microstructural tunability via field-assisted curing allows for application-specific optimization between precision and sensitivity. Randomly dispersed configurations provide strictly hysteresis-free operation (similar to 0 mT), whereas vertically aligned nanoparticle chains (Chain MFG) significantly amplify flux redirection efficiency. Although chain alignment introduces a small but finite residual hysteresis (0.3 mT), it achieves a 40% magnetic field conversion ratio and a threefold enhancement in z-axis sensitivity. This architectural flexibility bypasses the need for auxiliary coils, enabling a compact, power-efficient system realized through scalable inkjet printing. The platform's versatility is further demonstrated by a multi-axis force-sensing module capable of independently resolving normal and shear forces. This work establishes a practical platform bridging vector magnetometry and tactile sensing for next-generation wearable and human-machine interface applications.