Microstructural, interfacial, biological and electrical activity in sputtered Hydroxyapatite-Barium strontium titanate bilayered thin films

The article reports bilayered thin films of Ca10(PO4)6(OH)2, and Ba0.5Sr0.5TiO3 as coatings for implants in biomedical use. The films are fabricated using radio frequency magnetron sputtering, and two deposition conditions: Ba0.5Sr0.5TiO3 layer on top, Ca10(PO4)6(OH)2 beneath (both of same thickness), and Ca10(PO4)6(OH)2 layer on top and Ba0.5Sr0.5TiO3 beneath are considered in the study. The deposited films are then analyzed for their microstructural, surface, and electrical properties, along with their biocompatibility. In the microstructural analysis, the top layer of the films showed dominance in the X-ray diffraction pattern, and the scanning electron micrographs revealed highly dense uniform coverage over the substrates, a characteristic of sputtered films. Furthermore, the bilayers displayed hydrophobicity and are manifested in their excellent cell viability (>100%) that improved substantially with time. The dielectric properties revealed a modest dielectric constant in the range of 35–45, which can generate an internal polarized field that can assist the fracture healing process in the absence of the external stimulation. These insights help understand the role of electrical properties for healing wounds, which are scarcely studied but are found to play a dominant role in biomedical applications. In conclusion, the loss mechanisms in the films (leakage current) are analyzed to determine the parameters regulating the decay of polarized fields that can delay the healing process. The article essentially blends two critical phenomena: the hydrophobicity and electrical properties that are sparsely considered for understanding their biological implications that may aid in generating smart and advanced biomedical devices.