Short communication Quadrupolar magnetoresistor based on electroconductive magnetorheological elastomer Ioan Bica West University of Timis ¸ oara, Faculty of Physics, Bd. V. Pa ˆrvan, No. 4, 300223 Timis ¸ oara, Romania 1. Introduction Magnetoresistors are passive elements of an electric circuit. Their body is an active magnetic material. In Ref. [1] it is shown that the device made of a nonmagnetic tube which is connected at its ends with two electrodes and which contains the magnetor- heological suspension. We found that its electric resistance depends on the intensity and direction of the applied magnetic field. The change in the electric resistance of the magnetoresistor is due to the electric contact resistances occurring between the magnetic dipoles (directed along the magnetic field lines) in the liquid matrix [1–9]. As in the case of magnetorheological suspensions, aggregates are formed in magnetorheological elas- tomers (MREs) in magnetic field. Their strength depend on the strength of the applied magnetic field and on the magnetic properties of the magnetizable phase embedded in the elastic matrix. The formation of aggregates in the elastic matrix drastically modifies MREs viscoelasticity [10–13], a property used in achieving attenuators or/and absorbers of vibrations and mechan- ical shocks [12,13]. Recent researches [14–16] have shown that along the magnetic field lines the MREs band compresses reversibly. Because of this, the flat condenser with dielectric MRE reversibly modifies its electric capacity in magnetic field, a property which can be used in achieving traductors of pressure and force. Needles to say that electroconductive MREs represent an interesting class of smart materials for which are promising for new applications. One of these applications will be presented bellow. 2. Experimental studies The device consisting of two resistors with shared electro- conductive MRE is called quadrupolar magnetoresistor. The overall scheme of the quadrupolar magnetoresistor ‘‘CM’’ is indicated in Fig. 1. The ‘‘CM’’ body has the shape of a parallelipiped (Fig. 1). Its vat and its lid (Fig. 1a) are made of stratisticlotextolit. The electrodes 3 (Fig. 1a) are made of copper. The surface of the electrodes (Fig. 1a) is 50 mm  5 mm. In the distancers 2 in Fig. 1a, the electrodes are fixed. The dimensions of the electrodes are 15 mm  2 mm. Each electrode is provided with a connection terminal. The electroconductive MRE, is poured, in its liquid phase, into the vat 1 0 , by keeping fixed lid 1. An elastic body results after polymerization (position 5 in Fig. 1a), which adheres to the copper electrodes. The electric resistance of ‘‘CM’’ between the electrodes 3 is R L , while between the electrodes 4, the ‘‘CM’’ resistance is R T . The study of ‘‘CM’’ in magnetic field is achieved by using the experimental device in Fig. 2. The device (Fig. 2) includes an electromagnet consisting of the core 1 and the coil 2. Between the poles of the electromagnet (with the opening of 50 mm and the length of 100 mm) there are the ‘‘CM’’ and the Hall probe (position S in Fig. 2). The electrodes 3–3 0 of the ‘‘CM’’ are coupled to the digital ohmmeter R L , while the electrodes 4–4 0 are connected to the digital ohmmeter R T . Journal of Industrial and Engineering Chemistry 15 (2009) 769–772 ARTICLE INFO Article history: Received 18 May 2009 Accepted 23 June 2009 Keywords: Magnetorheological elastomer (MRE) Silicone rubber Magnetoresistor Magnetic field Electroconductivity ABSTRACT The quadrupolar magnetoresistor presented in this paper is based on the electroconductive magnetorheological elastomer (MRE) such as discussed in this paper. It is shown that the electric resistances on each pair of terminals of the magnetoresistor can be controlled by an external magnetic field. The results obtained are able to serve for several applications. ß 2009 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved. E-mail address: ibica2@yahoo.com. Contents lists available at ScienceDirect Journal of Industrial and Engineering Chemistry journal homepage: www.elsevier.com/locate/jiec 1226-086X/$ – see front matter ß 2009 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.jiec.2009.09.029