Nanotechnology-Enabled Sensors

Fig. 2.15 The Hall effect.
2.3 Physical Effects Employed for Signal Transduction 37
Commercial Hall effect sensors are utilized in sensing fluid flow, power,
and pressure sensing, yet they are most often employed for the measurement
of magnetic fields. In fact, planar Hall sensors have been used to
monitor magnetic fields in the nano-tesla range. 49 Being able to detect such
low magnetic fields, the Hall effect can be implemented in the development
of sensing systems which utilize nano-magnetic beads which generate
very small magnetic fields. A good example of this is provide by
Ejsing et al who have developed nano-magnetic bead sensors with sensitivities
in the order of 3 µV/Oe mA. Their sensor response to an applied
magnetic field of 250 nm magnetic beads which are commonly used for
biological applications 50,51