flakes Chromium Sio2 BaTiO3 CP-AFM NUS_Physics DNAProtein F14H20 WS2 single_layer PolyvinylideneFluoride C36H74 PVAC Spincast Piezoelectric SICM TipBiasMode pinpoint mode Graphite Biofilm OpticalWaveguide Fe_film Resistance Flake Current PECurve Lanthanum_aluminate thermoplastic_elastomers Conducting Insulator SrO hetero_structure neodymium_magnets AIN PvdfBead