Piezoresponse Friction Battery SurfaceChange Polyvinylidene HDD exfoliate SelfAssembly MoS2 BFO Step Treatment KPFM Polyethylene Logo chemical_compound CancerCell HumanHair Beads Non-ContactMode AdhesionForce Conductive AFM Optoelectonics ForceVolume gallium_nitride Anneal FM_SKPM Tungsten_disulfide ScanningSpreadingResistanceMicroscopy ContactMode UnivCollegeLondon Electical&Electronics DataStorage Tin disulfide FM-KPFM