Monitoring magnetostriction by a quantum tunnelling strain sensor

Hybrid materials offer the unique possibility to combine different functionalities of each component to obtain new classes of actuators or sensors. The hybrid material presented here consists of a macroscopic Terfenol-D crystal and a functional nanocomposite layer attached to its surface. The functional nanocomposite layer is made of polymer and Au nanoparticles in a regime near to the percolation threshold and embedded just below the polymer surface. Magnetically induced strain in the highly magnetostrictive Terfenol-D crystal leads to a change in interparticle distance between the metal nanoparticles and hence a change in quantum tunnelling properties through the two dimensional network of the Au nanoparticles. The electrical resistance of the nanocomposite layer allows direct measurement of the magnetically induced strain with a maximum change of 6% and can thus be used as a feedback sensor for the magnetostrictive actuator.