Composite polymer gels responsive to magnetic fields pp.447-476
Authors: (Tetsu Mitsumata, Department of Polymer Science and Engineering, Graduate School of Engineering, Yamagata University, Yonezawa, Japan)
Abstract: Magnetorheological properties of composite polymer gels and magnetic-gel actuators using the composite gels are described. Effects of magnetization on Young’s modulus of natural polymers gels and polyurethane elastomers containing magnetic particles have been investigated. These composite gels and elastomers demonstrated that the dynamic modulus remarkably decreased upon magnetization. In the case of the carrageenan magnetic gel, the modulus reduction exceeded 107 Pa. Both of the nonlinear viscoelasticity and the magnetostriction was observed in the composite gel, and is considered to be an important factor of the dynamic-modulus reduction. In the studies of the actuator, we fabricated a flexible fluid pump, high-power actuator, and drug delivery system using the magnetic composite gel. The pump consisting of sodium alginate and barium ferrite particles demonstrated rotational motion in response to rotational magnetic fields, and was achieved the maximum flow rates of 34 ml/min. The high-power actuator consisting of poly(vinyl alcohol) (PVA) and magnetic particles demonstrated elongation under non-uniform magnetic fields. We have fabricated a high-power actuator made of magnetic gels consisting of a thin magnetic-gel phase and a thick PVA-gel phase. A maximum strain of 33 % was achieved while sustaining a constant stress of 1.3 kPa using a magnetic field of 900 mT. The magnetic gel showed a maximum stress of 6.8 kPa and a strain of approximately 10 %. Magnetic gels consisting of two gel phases have great potential for application in practical actuators that can be driven by a magnetic field.