Advanced strategies for magnetic sensor integration with biomedical devices

By Dean Williams on June 2, 2017

Lead author Susana Cardoso de Freitas introduces the latest JPhysD Topical Review, Challenges and trends in magnetic sensor integration with microfluidics for biomedical applications S Cardoso et al 2017 J. Phys. D: Appl. Phys. 50 213001.

At INESC Microsistemas e Nanotecnologias (INESC-MN), work on magnetoresistive (MR) sensors started in 1994, with Professor Paulo P Freitas. The motivation was to improve the thin film materials and microfabrication processes to demonstrate sensing capabilities for 1 Gbit/in2 magnetic recording technologies. The competition with industry was enormous and stimulating, and has kept our group at the forefront of the research in magnetic thin film devices since.

When disk head prototypes at 1 Tbit/in2 where being qualified to production by industry in the 2000s, our research on magnetoresistive sensors needed to be redirected to future challenges. INESC-MN identified many unexplored applications in biotechnology and biomedical areas where the advanced magnetic sensors and related electronics for readout could bring additional advantages, compared with the conventional bench-top equipment available in biotechnologies. Following the impressive progress in biotechnology on the past decade, MR sensors could indeed be incorporated in many technological concepts, towards miniaturized devices for bio-research. Two examples are the detection of the magnetic fields created by synaptic currents and the detection of magnetic nanoparticle in cell labelling. One spin-off company (Magnomics) emerged from the INESC group in 2014 to reach the market with a portable magnetic lab-on-chip platform for DNA diagnostics, for animal health applications.

An example of low-cost and large-scale production compatible with semiconductor electronics fabrication at wafer level and the example layout of INESC-MN cytometer with the final device showing an MR chip bonded to the PDMS microﬂuidics. Wafer image reproduced from S Cardoso et al 2017 J. Phys. D: Appl. Phys. 50 213001, © IOP Publishing, All Rights Reserved. Image of cytometer Adapted from [1]. CC BY 4.0.

Many examples have been reported demonstrating the added value when MR sensors are combined with another technology. The increasing number of these reports motivated us to organize them in this Topical Review, using results from INESC-MN as a starting point, and extended to INL, where MR sensors have been qualified in multiple biomedical applications as well, within Professor Paulo Freitas’s team.

We show that magnetic biosensors have benefited greatly from the maturity of MR sensors, not only in the performance (field detectivity, large scale production, reliability), but also in the versatility that MR technology offers while integrating with most of the technologies supporting lab-on-a-chip devices. Three main areas are highlighted: microfluidics, implantable devices and flexible electronics.

Multi-project wafer production, available for CMOS, MEMS, RF or optical components, represent a growing market for biomedical-related applications. Within these, MR sensors have followed a consistent path toward monolithic integration with other components. The handling of the samples and the interaction with biological media (blood, tissues, etc) require specific solutions for the packaging and interfaces, never anticipated by the semiconductor industry. On the other hand, advanced neuroscience can find advantageous features in localized magnetic field sensing probes, for implantable probes. At the same time, the future generation of magnetic biochips will incorporate advanced nanoelectronics and the Internet of Things, following present societal demand. The multidisciplinary team at INESC MN surely demonstrate that smart people can develop smart systems.

About the authors

Susana Cardoso de Freitas

I was born in 1973 and received a PhD degree in Physics Engineering in 2002 from my work at INESC-MN on magnetic tape heads based on GMR and TMR technologies. Since then, I have worked in micro-nanotechnologies, with a special interest on thin film magnetic sensors and integrated devices. Being a professor at the Physics Department of the largest engineering university in Portugal (Instituto Superior Tecnico – Universidade de Lisboa), and also the mother of 5 children, imposes me the social responsibility of establishing a bridge between basic learning, creativity and technologies. I have the privilege to have Professor Paulo Freitas as my mentor for life, and his brilliant leadership in the Magnetics and Spintronics group at INESC-MN. Everyday I embrace work surrounded by very hard-working, creative, highly skilled and energetic young people (many of them women), who are fully engaged with the mission of developing applied research and getting their hands on experimental work. None of us can hide a profound satisfaction whenever a problem is solved, or the microfabricated device shows a good performance. INESC-MN provides an inspiring environment for the young people from many scientific areas that seek us as a platform for a career in Micro-Nanotechnologies, Sensors and Biomedical devices worldwide.

The INESC-MN team includes the researchers Diana C Leitao and Vania Silverio, and PhD students Tomas Dias, Joao Valadeiro and Marilia Silva.

(Left) In the deposition room, Joao Valadeiro, Vania Silverio, Susana Cardoso and Diana Leitao. (right) Tomás Dias, Diana Leitao, Prof. Paulo Freitas and inside the clean-room Marilia Silva accompanied by INESC MN students.

This work is licensed under a Creative Commons Attribution 3.0 Unported License.