FFM Optical TipBiasMode Microchannel Regensburg Ptfe Piranha single_layer Optoelectronic Polarization DNAProtein ito_film EFMAmplitude graphene_hybrid temp_control Biology UnivCollegeLondon HafniumDioxide temp Magnetostrictive Polyethylene NUS_Physics AdhesionForce HexagonalBN TappingMode ScanningIon-ConductanceMicroscopy 2d_materials LiIonBattery Chemical_Vapor_Deposition Graphene Semiconductor Ni-FeAlloy Grain Fujian Corrosion