Fabrication and characterization of ultra-soft PDMS based magnetorheological elastomers*

Magnetorheological elastomers (MREs) are composite materials consisting of elastomer matrix with embedded micro- or nano- sized ferromagnetic entities. Ultra-soft PDMS based MREs are promising candidates for dynamic cell culture substrata. In this work, we report the fabrication and magnetic characterization of PDMS based MREs. Sylgard 527 and carbonyl iron powder were mixed together at various ratios and cured at 60⁰C for 24 hours without applied magnetic field and with applied magnetic field of various field strength. Angular dependent magnetic hysteresis loops of MREs were measured using a vibrating sample magnetometer. MREs cured without magnetic field show no angular dependence in the major hysteresis loop, consistent with the isotropic distribution of iron particles in the MREs. Instead, hysteresis loops for MREs cured in magnetic field clearly display anisotropy as expected. The different first order reversal curve (FORC) distribution characteristics of the isotropic and anisotropic MREs agree with the structural difference of these two types of MREs.