Giant magneto resistance sensor: (a) test card, (b) multilayer structure of the test card, (c) GMR chip and the connection between the GMR chip and PCB, (d) structure of the microchannel system, and (e) reaction process of the GMR multibiomarker immunoassay. Reprinted from Biosensors and Bioelectronics, Vol. 123, Gao, Y.; Huo, W.; Zhang, L.; Lian, J.; Tao, W.; Song, C.; Tang, J.; Shi, S.; Gao, Y. Multiplexed measurement of 12 tumor markers using a GMR multibiomarker immunoassay biosensor, pp. 204–210 (ref 61). Copyright 2019, with permission from Elsevier.