2-vinylpyridine CalciumHydroxyapatite OpticalWaveguides MechanicalProperties BiVO4 kelvin probe force microscopy Tapping Au111 norganic Polypropylene Battery Ptfe Piezoresponse Copolymer Phthalocyanine Varistor BariumTitanate PECurve PetruPoni bias_mode MonoLayer Polyvinylidene Thermoplastic_polyurethane Vortex Korea Magnetic FFM Tin sulfide EPFL Vinylpyridine AnodizedAluminumOxide AAO Potential Water self-assembly