More than Magnetic: Iron Magnetoresistors
Nok Yin Noreen Chan
University Transition Program
Floor Location : J 201 D

This project began with an inquiry into the applications of magnetoresistive biosensors. The biosensor determines the amount of a pathogen or toxin present in a sample area. It does this by sensing the resistance of Super Paramagnetic Iron Oxide (SPIO) nanoparticles that have attached to a target species under the application of an external magnetic field. I designed my own experiment to test a magnetic field’s effect on the resistance of paramagnetic objects.

In the experiment, several iron filing mixtures were made by adding increments of filings into suspending fluids taken from a stock mixture of cornstarch and water. Each iron filing mixture was then poured into a container with two metal strips attached to the sides (for the multimeter probes to rest on), and the mixture’s resistances were measured twice: once with and once without an external magnetic field. Based on these measurements, the percentage decrease of the fluid’s resistance after applying the magnetic field was found to be around 6.9 ± 0.2 kΩ. This proved my first hypothesis, which was that the ratio of the resistances between magnetized and unmagnetized iron filing mixtures will remain constant as the percentage of iron filings increases. However, my second hypothesis (the resistance of the iron filing mixture will decrease as the percentage of iron in the mixture increases) was disproven as there was no trend between the resistance and the amount of filings. This may be due to the imprecision of the measurement instrument (multimeter) or the fact that the experiment was done over several hours, allowing water to evaporate from the stock mixture.

Afterward, applications of paramagnetic particles and magnetoresistance were researched, especially one which involved the use of magnetoresistive sensors and SPIO nanoparticles. As this method of measuring species on the nano scale does not require expensive lab equipment or a long analysis time, it can reach many patients. The beads’ production process and an explanation of how they allow a biosensor to determine the amount of a target species were also investigated.

The results of the experiment and the research in this project can be further investigated to develop future biomedical tools for analyzing diseases, cancers, and toxins.