Microfluidic microsystem for magnetic sensing of nanoparticles with Giant Magneto-Impedance technology

We have fabricated a microfluidic microsystem integrating a Giant Magneto-Impedance wire sensor that successfully detected the passage of magnetic nanoparticules in liquid medium. Giant Magneto-Impedance microwire sensors consisted in CoFeSiBNb alloy, 40 μm diameter and 1 cm long wires. By magnetizing the magnetic nanoparticles in the liquid perpendicularly to the sensitive axis of the Giant Magneto-Impedance microwire sensor, we have observed magneto-impedance signal variations induced by the magnetic dipole field from the magnetic nanoparticles. A peak detector was used to measure the voltage signal due to the magneto-impedance variations. The voltage signal was subsequently demodulated by a lock-in amplifier.