Inkjet-printed flexible piezoelectric sensor for self-powered biomedical monitoring

Printed electronics has enabled fabrication of electronic components and devices with low cost and more manufacturing and design freedom. This manufacturing technique has been successfully employed as a complementary fabrication approach to conventional nanolithography and microfabrication processes to create flexible and stretchable electronics. Fluoropolymers are crucial components in electronic devices and components, owing to their piezoelectric, triboelectric, pyroelectric, ferroelectric, and dielectric properties. In this research, we report fabrication of an inkjet-printed piezoelectric sensor based on poly (vinylidenefluoride trifluoroethylene) (PVDF-TrFE) and amine functionalized graphene oxide (AGO) for biomedical monitoring. The piezoelectric inkjet ink was obtained by optimizing the fluid mechanic properties based on Reynold and Weber numbers. The inkjet-printed freestanding film was characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), wide-angle X-Ray scattering (WAXS), and differential scanning calorimetry (DSC). The piezoelectric sensor was fabricated by deposition of silver electrodes on each side of the piezoelectric film, followed by wiring and encapsulation. The sensor was subjected to an electric field of 1500 kV/cm to align the internal dipoles and induce net polarization. The fabricated flexible piezoelectric sensor was employed for monitoring biomedical signals such as finger tapping, joint bending, and swallowing. The sensor demonstrated outstanding sensitivity of 0.1 V/kPa and excellent repeatability and stability over 1000 cycles.