Actuating properties of soft gels with ordered iron particles: basis for a shear actuator

Soft electrorheological (ER) gels were prepared by arranging iron particles in silicone prepolymers within magnetic fields and crosslinking the obtained structure. The gap between the particles, and consequently the conductivity, was controlled by swelling the crosslinked material with additional silicone prepolymer. Iron-particle chains were made with as little as 0.5% particles and at angles from 0degrees to 60degrees to the normal of the sample surface. The ER, transducing and actuating properties of these materials were explored using rheometry and dielectrometry. In general, the dynamic shear moduli of the aligned ER gels increased quadratically with the electric field intensity. With only 1 vol% particles, the modulus doubled to an electrical field of around 2 kV mm(-1). Transducer and actuator properties were noted. With particle chain alignment of 30degrees, shear stresses of around 150 Pa were measured with a special sandwich-type shear fixture. The influence of tilt angle on the shear stress was found to be qualitatively consistent with the calculation based on the point-dipole approximation.