A theoretical model for the field-dependent conductivity of magneto-rheological gels and experimental verification

• A theoretical model of magneto-rheological gel was developed to precisely predict the magnetic field-dependent conductivity of MRG.
• Several samples of magneto-rheological gel were fabricated and their magneto-resistance properties were explored at different magnetic fields.
• The effectiveness of the proposed model was validated through a comparative work between measured results and theoretically obtained results.
• It is shown that the proposed model can reproduce well experimental results without causing significant difference.
• This theoretically model is expected to provide guidance for magneto-rheological gel applied to many potential fields, such as the magnetic sensor.

A magneto-rheological gel (MRG) is a kind of smart material fabricated by dispersing ferromagnetic particles in high viscosity polymer gel. The internal particles of MRG are uniformly dispersed under off-state. While with the precondition of an external applied magnetic field, the particles will form a reversible chain-like structure, in which process the electrical resistivity of MRG has an immense change. In order to deeply understand the changing mechanism of the magneto-resistance of MRG, a theoretical model based on both the magnetic-dipole behavior and the percolation theory was proposed in this work. This model incorporates the parameters of the magnetic field intensity and carbonyl iron powder (CIP) volume fraction. As a further effort to explore the magneto-resistance properties of MRG, a series of experimental testing were conducted. The magneto-resistance properties of MRG with different CIP volume fractions and under different magnetic fields were investigated. The experimental results indicated that the conductivity of MRG was significantly increased with the increasing magnetic field and CIP volume fraction. In addition, in order to verify the effectiveness of the proposed theoretical model, the experimental measured results and theoretically obtained results were compared. The validation results demonstrated that the theoretical model proposed in this work is capable of reproducing the field-dependent magneto-resistance properties of MRG.