self_healing thermoplastic_elastomers DomainSwitching Ca10(PO4)6(OH)2 Growth StyreneBeads Pzt ItoGlass Gold SPMLabs NUS Forevision MBE HexagonalBoronNitride CopperFoil Pvdf Graphite IISCBangalore cross section Sio2 LateralPFM NUS_Physics PDMS VerticalPFM Sic Thermal Topography align Pinpoint piezoelectric force microscopy UnivMaryland India Inorganic_Compound Led Fe_film