Design and fabrication of high-dielectric BaTiO₃/polyimide composite film with impedance gradient

The dielectric constant of human skin and air have a large mismatch. The materials used for wearable devices need to have a great matching performance with human shin, which can not be achieved by solo material and structure. By using the in-situ polymerization method, a series of barium titanate (BaTiO₃)/polyimide(PI) mixed solutions were synthesized. Then, by means of casting method step by step, a multilayer BaTiO₃/PI composite film with impedance gradient was designed and fabricated. The results show that BaTiO₃ nano-particles can distribute in the composite film uniformly. By adjusting the content of inorganic particles, the dielectric constant of prepared BaTiO₃/PI composite film can be controlled in the range of 2.5-34.0. Besides, BaTiO₃/PI composite film is insensible to the frequency of electric field and also has a good mechanical property, which can meet the requirements of wearable device materials.