Schematic illustration of the preparation of capturing antibodies biofunctionalized MTJ sensor. (a) One droplet of antibody solution was introduced onto the sensor sensing area surface. (b) Capturing antibodies were passively attached to the surface of MTJ sensor by incubation in buffer. (c) Blocking buffer was added to eliminate non-specific binding effect and block the remaining active area (blocking areas are represented by red color). (d) A biofunctionalized MTJ sensor was achieved.