Detection of $130\mathrm{nm}$ magnetic particles by a portable electronic platform using spin valve and magnetic tunnel junction sensors

An integrated biosensor with magnetic tunnel juntions (MTJs) and spin valve (SV) sensor was used for $130\mathrm{nm}$ particle detection. A platform drives an external magnet generating an in-plane $\mathrm{dc}+\mathrm{ac}$ magnetic field on the sensor at frequencies up to $375\mathrm{Hz}$, provides a current to bias the sensor, and performs the signal acquisition and treatment. The signal-to-noise ratio of the SV and MTJ was characterized. Bead detection ($130\mathrm{nm}$ in diameter) was performed using both sensors leading to a detection limit of $3\times {10}^8\text{particles}∕\mathrm{ml}$ for SV and $3\times {10}^{10}\text{particles}∕\mathrm{ml}$ for MTJ.