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 (∼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.