Carbon nanofiber-polyelectrolyte triggered piezoelectric polymer-based hydrophilic nanocomposite for high sensing voltage generation

Abstract

Flexible electronic devices with flexible sensors have drawn enormous attention due to their wide variety of applications, such as wearable health monitoring devices, bendable touch screens, flexible storage devices, artificial skins, etc. However, the mechanical and electrical performance of devices should be enhanced by new materials design or an innovative device structure to fulfill the requirements for such applications. Here, a poly(vinylidenefluoride) (PVDF) piezoelectric polymer-based hydrophilic nanocomposite (PHNC) sensing membrane using carbon nanofibers (CNF) and poly-acrylamido-methyl-propane-sulfonic acid (PAMPS) polyelectrolyte exhibiting enhanced mechanical and electrical performance is demonstrated. The hydrophilic PAMPS intruded in the PVDF/CNF composition, triggering microstructural changes and facilitating a strong polar β-phase PVDF formation. A dc conductivity of 0.43 S/cm and high electric current density (3.64 μA/cm2) were achieved from PVDF/CNF/PAMPS (80/2/18) PHNC. The piezoelectric performance of the PHNC was investigated for several bending cycles, and it generates the maximum peak output voltage up to 3.65 V under the repeated bending-releasing test procedure. A wearable sensor application is demonstrated by exposing it to different human body movements. During finger motion and elbow movements, the developed PHNC generated piezoelectric maximum peak output voltage up to 3.58 V at a bending angle of 180° for finger motion and 2.2 V for elbow movement. The fabricated PHNC are highly flexible and exhibit outstanding reproducibility and reliability, making them ideal for energy harvesting, the self-powered sensor in wearable electronic devices, electronic skin (e-skin), and soft robotics applications.