Published online by Cambridge University Press: 15 February 2011
We have investigated regional variations of elastic properties using a magnetic force controlled AFM. A piece of small magnet was fixed at the end of the backside of the AFM cantilever so as to apply forces directly to the tip through the external magnetic field of an electromagnet. By modulating the applied forces to the tip and measuring the resulting amplitude of oscillation, a sensitive measurement of the local contact stiffness can be made. We have applied this technique to phase-separated films of polystyrene/polymethylmethacrylate (PS-PMMA) which have almost identical Young's moduli.