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31 March 2009Electrical and magneto-resistance of Co/CNT/Epoxy thin film for strain and magnetic field sensing
Cobalt and iron nanoparticles are doped in carbon nanotube (CNT)/polymer matrix composites and studied
for strain and magnetic field sensing properties. Characterization of these samples is done for various volume
fractions of each constituent (Co and Fe nanoparticles and CNTs) and also for cases when only either of the
metallic components is present. The relation between the magnetic field and polarization-induced strain are
exploited. The electronic bandgap change in the CNTs is obtained by a simplified tight-binding formulation in
terms of strain and magnetic field. A nonlinear constitutive model of glassy polymer is employed to account for
(1) electric bias field dependent softening/hardening (2) CNT orientations as a statistical ensemble and (3) CNT
volume fraction. An effective medium theory is then employed where the CNTs and nanoparticles are treated
as inclusions. The intensity of the applied magnetic field is read indirectly as the change in resistance of the
sample. Very small magnetic fields can be detected using this technique since the resistance is highly sensitive to
strain. Its sensitivity due to the CNT volume fraction is also discussed. The advantage of this sensor lies in the
fact that it can be molded into desirable shape and can be used in fabrication of embedded sensors where the
material can detect external magnetic fields on its own. Besides, the stress-controlled hysteresis of the sample
can be used in designing memory devices. These composites have potential for use in magnetic encoders, which
are made of a magnetic field sensor and a barcode.
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Sandeep V. Anand, Rejin Isaac, D. Roy Mahapatra, "Electrical and magneto-resistance of Co/CNT/Epoxy thin film for strain and magnetic field sensing," Proc. SPIE 7291, Nanosensors, Biosensors, and Info-Tech Sensors and Systems 2009, 72910O (31 March 2009);