Graphene Oxide Papers in Nanogenerators for Self-Powered Humidity Sensing by Finger Tapping

Faezeh Ejehi,Elham Asadian,Somayeh Fardindoost,Omid Akhavan,Raheleh Mohammadpour,Pezhman Sasanpour

doi:10.1038/s41598-020-64490-7

Abstract

Triboelectric nanogenerators (TENGs) offer an emerging market of self-sufficient power sources, converting the mechanical energy of the environment to electricity. Recently reported high power densities for the TENGs provide new applications opportunities, such as self-powered sensors. Here in this research, a flexible graphene oxide (GO) paper was fabricated through a straightforward method and utilized as the electrode of TENGs. Outstanding power density as high as 1.3 W.m−2, an open-circuit voltage up to 870 V, and a current density of 1.4 µA.cm−2 has been extracted in vertical contact-separation mode. The all-flexible TENG has been employed as a self-powered humidity sensor to investigate the effect of raising humidity on the output voltage and current by applying mechanical agitation in two forms of using a tapping device and finger tapping. Due to the presence of superficial functional groups on the GO paper, water molecules are inclined to be adsorbed, resulting in a considerable reduction in both generated voltage (from 144 V to 14 V) and current (from 23 µA to 3.7 µA) within the range of relative humidity of 20% to 99%. These results provide a promising applicability of the first suggested sensitive self-powered GO TENG humidity sensor in portable/wearable electronics.

Highlights

Among the various energy-related materials, graphene-based materials have been studied extensively in the field of energy harvesting in recent years[12]
graphene oxide (GO) humidity sensors operate on the basis of detecting the variation of impedance or capacitance due to the inclination of the water molecules to adsorb on the surface of GO21–26
Flexibility is a key factor for utilizing a sensor in wearable electronics, which was not considered in many previous studies of Triboelectric nanogenerators (TENGs)-based humidity sensors

Summary

Introduction

Among the various energy-related materials, graphene-based materials have been studied extensively in the field of energy harvesting in recent years[12]. Applying the as-fabricated GO TENG as a self-powered humidity sensor is reported for the first time in this paper. Investigations of humidity sensing were performed on large and small sizes of the electrodes, which present the fabricated TENG as an applicable option for portable devices, as well as industrial implementations.

Results

Conclusion