An innovative method for the preparation of elastomeric magnetic films with increased magneto-responsivity is presented. Polymeric films containing aligned magnetic microchains throughout their thickness are formed upon the magnetophoretic transport and assembly of microparticles during polymer curing. The obtained films are subsequently magnetized at a high magnetic field of 3 T directed parallel to the orientation of the microchains. We prove that the combination of both alignment of the particles along a favorable direction during curing and the subsequent magnetization of the solid films induces an impressive increase of the films' deflection. Specifically, the displacements reach few millimeters, up to 85 times higher than those of the nontreated films with the same particle concentration. Such a process can improve the performance of the magnetic films without increasing the amount of magnetic fillers and, thus, without compromising the mechanical properties of the resulting composites. The proposed method can be used for the fabrication of magnetic films suitable as components in systems in which large displacements at relatively low magnetic fields are required, such as sensors and drug delivery or microfluidic systems, especially where remote control of valves is requested to achieve appropriate flow and mixing of liquids.
Keywords: PDMS; ferromagnetism; magnetic actuation; magnetic assembly; microparticles.