Sphere Photovoltaics cooling ScanningKelvinProbeMicroscopy Flake Graphene Foil PS_PVAC Polyvinylidene NUS_Physics PolyimideFilm Blend FM_SKPM kelvin probe force microscopy CeNSE_IISc self_assembly Hexylthiophene FFM PhaseChange BiVO4 lithography Melt MagneticPhase PolyvinylideneFluoride LMF dielectric_trench DNAProtein PolyvinylAcetate H-BN temp Ptfe HydroGel INSP Roughness Aluminum