Proof of concept of a two-stage GMR sensor-based lab-on-a-chip for early diagnostic tests

The development of rapid, sensitive, portable and inexpensive early diagnostic techniques is a real challenge in the fields of health, defense and in the environment. The current global pandemic has also shown the need for such tests. The World Health Organization has defined ASSURED criteria (affordable, sensitive, specific, user-friendly, rapid and robust, equipment-free and deliverable to end-users) that field diagnostic tests must fulfill, which proves the real need in terms of public health. Giant magnetoresistance (GMR) sensors, which have flourished in a wide variety of spintronic applications (automobile industry, Information Technology, etc.), also have real potential in the field of health, particularly for the development of early diagnostic point-of-care devices. This work presents a new type of innovative biochip, consisting of GMR sensors arranged on both sides of a microfluidic channel which allow on the one hand to count magnetic objects one by one but also to better distinguish false positives (aggregates of beads, etc.) from labelled biological targets of interest by determining their magnetic moment. We present the operating principle of this new tool and its great potential as a versatile diagnostic test.