Carbon fabric coated with nanostructured zinc oxide layers for use in triboelectric self-powered touch sensors

Abstract

An environmentally friendly, low-cost, and lightweight biocompatible textile triboelectric material was made by in situ coating carbon fabric (CF) with nanostructured zinc oxide (ZnO) layers using the automatic Successive Ionic Layer Adsorption and Reaction (SILAR) method. Depending on the deposition mode, we created triboelectric CF/ZnO textiles with multidirectionally intergrown short ZnO nanorods or with arrays of ZnO nanosheets. The Raman spectra confirmed the hexagonal wurtzite structure of both types of ZnO layers and the unique a-axis texture of the nanosheets. In the developed triboelectric CF/ZnO/PET/ITO sensors, the upper tribonegative part was made of a polyethylene terephthalate film coated with a thin layer of indium-tin oxide, and the lower tribopositive part was made of CF/ZnO textile. In tests with repeated hand tapping at low frequency 1.3–13 Hz and a force of ∼ 5 N (pressure of ∼ 33 kPa), the open-circuit voltage pulses were ∼ 15 V for short ZnO nanorods and ∼ 30 V for ZnO nanosheets, their duration did not exceed a few milliseconds. Due to the nanosheet morphology of the ZnO layer, the maximum touch-induced surface charge density for the corresponding triboelectric textile (0.7 µC/m2) was almost twice than for the CF/ZnO textile with intergrown ZnO short nanorods (0.4 µC/m2). The touch sensor with ZnO nanosheets showed an output voltage of 3.6 V, a current density of 1.47 µA/cm2, and a power density of 1.8 µW/cm2. It can be used as a dual-mode sensor due to ability to recognize the hardness of objects by analyzing the output current peaks.