A Low Noise CMOS Sensor Frontend for a TMR-based Biosensing Platform

In this paper, we propose a low noise CMOS frontend for a Point-of-Care (PoC) biosensing platform based on tunnel magnetoresistance (TMR) as sensors. The integration of a low noise and low power integrated circuit (IC) with the TMR sensors reduces power consumption compared to a realization with discrete electronics, and thereby paves the way towards a portable diagnostic system. The proposed chip uses a DC-coupled fully differential difference amplifier (FDDA) to amplify the minute signals generated by magnetic nanotags (MNTs) that will be used as biomarkers in the target biosensing application. The FDDA features a gain of around 60dB with a suitable offset calibration scheme to deal with the large DC offsets caused by TMR and/or magnetic field variations. The ability to deal with changing DC fields is crucial for a portable setup that is intended to be used in unshielded environments outside the lab. The offset cancellation is achieved by two on-chip current steering DACs that can accommodate TMR resistances between 535Ω and 4.7kΩ. The presented chip is manufactured in a 180nm SOI CMOS technology and features a thermal noise floor of 7nV/√Hz. It consumes a total of 7.7mA from a 1.8V supply

Magnetoresistive biosensors with on-chip pulsed excitation and magnetic correlated double sampling.

Giant magnetoresistive (GMR) sensors have been shown to be among the most sensitive biosensors reported. While high-density and scalable sensor arrays are desirable for achieving multiplex detection, scalability remains challenging because of long data acquisition time using conventional readout methods. In this paper, we present a scalable magnetoresistive biosensor array with an on-chip magnetic field generator and a high-speed data acquisition method. The on-chip field generators enable magnetic correlated double sampling (MCDS) and global chopper stabilization to suppress 1/f noise and offset. A measurement with the proposed system takes only 20 ms, approximately 50× faster than conventional frequency domain analysis. A corresponding time domain temperature correction technique is also presented and shown to be able to remove temperature dependence from the measured signal without extra measurements or reference sensors. Measurements demonstrate detection of magnetic nanoparticles (MNPs) at a signal level as low as 6.92 ppm. The small form factor enables the proposed platform to be portable as well as having high sensitivity and rapid readout, desirable features for next generation diagnostic systems, especially in point-of-care (POC) settings

Magnetic biosensors: modelling and simulation

In the past few years, magnetoelectronics has emerged as a promising new platform technology in various biosensors for detection, identification, localisation and manipulation of a wide spectrum of biological, physical and chemical agents. The methods are based on the exposure of the magnetic field of a magnetically labelled biomolecule interacting with a complementary biomolecule bound to a magnetic field sensor. This Review presents various schemes of magnetic biosensor techniques from both simulation and modelling as well as analytical and numerical analysis points of view, and the performance variations under magnetic fields at steady and nonstationary states. This is followed by magnetic sensors modelling and simulations using advanced Multiphysics modelling software (e.g. Finite Element Method (FEM) etc.) and home-made developed tools. Furthermore, outlook and future directions of modelling and simulations of magnetic biosensors in different technologies and materials are critically discussed