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Su et al. J Cancer Metastasis Treat 2020;6:19 I http://dx.doi.org/10.20517/2394-4722.2020.48 Page 11 of 21

A B

C D

E

Figure 5. The Z-lab device can be connected to multiple types of devices such as cell phones, tablets, laptops, and desktop computers
(A); the Z-Lab platform consists of three parts: a plastic cartridge, an electrical interface connecting the electrodes from GMR chip to
the circuit board, and a handheld device (B); the layout of the GMR sensors (C); schematic illustration of the magnetic immunoassays
on the sensor surface (D); real-time binding curve readout from Z-lab device (E) [50] (reprinted with permission from American Chemical
Society). GMR: giant magnetoresistance

of the GMR-CMOS interface in addition to noise removal circuit for such handheld device, thereby
immensely contributing to the sensitivity of the handheld device [79,80] .

NMR
Origin of NMR signal
1
15
31
17
Elements that contain an odd number of protons and/or neutrons, such as H, N, O, P, etc., show
intrinsic nonzero nuclear spins that give rise to small magnetic moments which can be observed by the
NMR spectroscopy. Under a strong constant magnetic field B , the magnetic moments are in equilibrium
0
states, i.e., aligned either with or against the field denoted as M in Figure 6A [81,82] . A perturbation of the
0
nuclear spins from equilibrium will occur when a weak oscillating magnetic field [referred to as radio
frequency (rf) pulse] is applied whose frequency closely matches the nuclei’s intrinsic Larmor frequency.