mechanical property Mobile Ni81Fe19 MagneticForce molecule NTU SiWafer kelvin probe force microscopy Memory Step FM-KPFM EFM LDPE Ferrite KAIST Permalloy MeltingPoint CopperFoil Sio2 InsulatorFilm align Moire Pipette CuFoil PyroelectricDetector LateralForceMicroscopy PDMS Crystal Potential 2dMaterials PUR MolecularSelfAssembly doped PetruPoni_Institute TipBiasMode