epitaxy ring shape Annealing Wang norganic FrictionalForce NeodymiumMagnets TPU KPFM Neodymium Chungnam_National_University HafniumDioxide Wildtype Polymer Zhi Singapore ForceVolumeMapping Battery light_emitting AM-KPFM Yeditepe_University lithography LifeScience PMNPT HDD Polydimethylsiloxane TiO2 MultiferroicMaterials ElectroChemical HanyangUniv PS_LDPE Polyurethane self-assembly OxideLayer Silicon