Electronic Platforms and Signal Processing for Magnetoresistive-Based Biochips

Abstract

Due to nanotechnology advancements, very high sensitivity and low-noise magnetoresistive (MR) sensors have been fabricated at the nanoscale, thus allowing a high spatial resolution for magnetic field measurements. Due to such characteristics, they have been used in the last decade for biochip applications, such as biomolecular recognition, and, more recently, neuronal magnetic recording. In the biomolecular recognition application, MR sensors provide a much higher performance solution when compared to common fluorescence-based systems, decreasing the limit of detection in several orders of magnitude, into the femtomolar range. In the neuronal recording field, MR sensors are capable of detecting the magnetic field generated by the flow of ionic currents in the neurons with excellent spatial resolution, which can bring new and valuable information about the way neurons communicate with each other, complementing the typical microelectrode arrays, which measure the extracellular voltage of neurons. In addition, MR sensors are galvanically isolated from the brain, thus avoiding problems related to cicatrization that results from electrode implantation. In order to take advantage of the MR sensor characteristics described above, very high-performance electronics must be developed in order to extract the information from the MR sensors. In addition, proper software tools should also be engaged, with the purpose of providing further signal processing and allowing signal visualization adapted to the respective application. This chapter describes examples of the integration of MR sensors in biochip platforms and the specific interface electronics for these platforms.