INVESTIGADORES
NEGRI Ricardo Martin
artículos
Título:
Superparamagnetic anisotropic elastomer connectors exhibiting reversible magneto-piezoresistivity
Autor/es:
MIETTA, J.L.; JORGE, G.; PÉREZ, O.E.; MAEDER, T.; NEGRI, R.M.
Revista:
SENSORS AND ACTUATORS A-PHYSICAL
Editorial:
ELSEVIER SCIENCE SA
Referencias:
Lugar: Amsterdam; Año: 2013 vol. 192 p. 34 - 41
ISSN:
0924-4247
Resumen:
An anisotropic magnetorheological composite formed by dispersions of silver-covered magnetite microparticles
(Fe3O4@Ag) in polydimethylsiloxane (PDMS) displaying electrical conduction only in one
preferred direction is presented. A set-up for applying and detecting electrical conduction through the
composite is described and applied to characterize the behavior of the system in onoff commutation
cycles. The composite is obtained by loading the polymer with relatively low concentration of fillers (5%,
w/w of the total weight) and curing it in the presence of a uniform magnetic field. The fillers appear in
the final composite as an array of needles, i.e. pseudo-chains of particles aligned in the direction of the
magnetic field. Using Fe3O4 nanoparticles (13 nm) it is possible to obtain cured composites in a superparamagnetic
state, that is, without magnetic hysteresis at room temperature. Hysteresis is not found in
the elastic properties either; in particular, Mullins effects (change of physical properties after the first
strainstress cycle) were not observed.
No measurable transversal electrical conduction was detected (transversal resistivity larger than
62 M cm). Thus, significant electrical conductivity is present only between contact points that are
exactly facing each other at both sides of the composites in the direction parallel to the needles. The IV
curves in that direction have ohmic behavior and exhibit both piezoresistance and magnetoresistance,
that is, the electrical conductivity in the direction parallel to the pseudo-chains increases when a pressure
(i.e. compressive stress) is applied at constant magnetic field and/or when a magnetic field is applied
at constant pressure. The materials do not exhibit magnetoelectric or piezoresistive hysteresis. These
characteristics illustrate the high potentiality of these systems in elastic connectors where electrical
conduction can be varied by external mechanical or magnetic forces.
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