kelvin probe force microscopy Edwin self-assembly Biofilm BariumTitanate PetruPoni food Worcester_Polytechnic_Institute Bmp TungstenThinFilmDeposition TappingMode conductive VortexCore nanomechanical mono_layer SAM Ceramic margarine FrequencyModulation Polymer Steps LiftMode Copper CompactDisk SelfAssembly DiffractiveOpticalElements Bacteria Strontium polymeric_arrays Floppy light_emitting Genetic Heating AM-KPFM high_resolution