In-line monitoring of magnetic nanoparticles synthesis using reactor integrated on-chip magnetometer

The excellent multifunctional properties of magnetic nanoparticles (MNPs) allow them to be used in a wide range of applications. However, the required processes for the MNPs synthesis and characterization are still time-consuming and laborious, which further delays the research and development of the synthesis of MNPs. To overcome these difficulties, an on-chip magnetometer consisting of a planar Hall magnetoresistive (PHMR) sensor with a reactor was developed to optimize synthesis conditions for MNPs effectively. The microreactor was fabricated on the PHMR sensor, and the induced field from the synthesized magnetic particles was directly detected in the form of an output signal. Since the on-chip magnetometer enables simultaneous synthesis and measurement, it successfully monitored from the start point to the endpoint of the MNPs synthesis reaction. We studied the effect of the reagent ratio on the particle with iron chloride and aqueous ammonia solution, and we found the most suitable combination using a multi-array on-chip magnetometer. Experiments under various conditions were conducted simultaneously, and the experimental conditions were optimized in a short duration of time. Even though the synthesis reaction took place in a short time, the sensor's fast measurement rate and sensitivity allowed in-line measurement of the particle formation process. In addition, the developed on-chip magnetometer can be flexibly combined according to the desired configuration. Therefore, it is expected to be widely used as a new device for the simultaneous synthesis and analysis of MNPs.