Zinc oxide nanorods and nanotubes arrays grown on carbon fabric by microwave hydrothermal method for self-powered piezoelectric/triboelectric sensors

Abstract

The development of efficient piezoelectric/triboelectric textile materials for highly sensitive wearable autonomous pressure, shock and vibration sensors holds promise for use in health monitoring, motion detection, human-machine interaction, and active touch matrices for electronic skin of soft robots. In this work, arrays of zinc oxide nanorods (ZnONR) and nanotubes (ZnONT) oriented vertically on the surface of carbon fabric (CF) were grown from aqueous solutions with concentrations of zinc nitrate and hexamethylenetetramine (HMTA) in the range of 50–100 mM using a seed-mediated microwave hydrothermal method. The results of tests of experimental samples of pressure and impact sensors based on various compositions of double-electrode and single-electrode piezoelectric/triboelectric nanogenerators (PTENGs) of contact-separation mode with textile parts of CF/ZnONR and CF/ZnONT confirmed the coupling of piezoelectric and triboelectric effects. The tests have shown that the efficiency of all developed PTENGs increases with increasing contact area of nanostructured zinc oxide arrays, and therefore ZnO nanorods have proven to be more promising for use in all types of PTENGs. The best responses were recorded for pressure, impact and vibration sensors based on PTENG with a piezoelectric/triboelectric textile part CF/ZnONR obtained by the microwave hydrothermal method in the solution of 100 mM Zn(NO₃)₂ and 100 mM HMTA. Comparison of their sensitivity with the sensitivity data of wearable triboelectric pressure and strain sensors, as well as hybrid piezotriboelectric and triboelectric flexible vibration sensors, showed that the sensitivity data obtained in this work is on the same level or superior to the best state-of-the-art.