Hydrophobic Fully Wearable Piezoelectric WS2 Quantum Dot-Polyaniline-Based Nanogenerator

Abstract

In this work, we report the synthesis and fabrication of a fully wearable piezoelectric nanogenerator based on hydrothermally grown tungsten disulfide (WS₂) quantum dots and dip-coated conductive polyaniline (PANI) on cotton fabrics. WS₂ quantum dots with a hexagonal crystal structure and an average diameter of 7–8 nm were confirmed by X-ray diffraction and a high-resolution transmission electron microscope. A fully wearable nanogenerator was constructed using a poly(methacrylic acid methyl ester) (PMMA) matrix for WS₂ QDs and conductive PANI deposited on the cotton fabric. Conductive PANI coated on cotton fabric was used as the top and bottom electrodes. Functional group and distribution of the WS₂QDs inside PMMA were confirmed through the Fourier transform infrared spectroscopy (FT-IR) and field emission scanning electron microscopy techniques. A fully wearable WS₂ QDs-PMMA-cotton, PANI-based nanogenerator generated a very high output voltage of 60 V and a current density of 302 nA/cm² under vertical mechanical strain. Interestingly, the WS₂ QDs-PMMA-cotton based nanocomposite showed a very dielectric constant (έ) of 799 at 1.5 kHz. The wearable nanogenerator based on the WS₂ QDs-PANI fabric-based nanocomposite exhibits a high power density. Moreover, the device shows a high tensile strength of 60.25 MPa, confirming robust performance of the wearable nanogenerator. The output performance of the wearable WS₂ QDs-PANI nanogenerator is measured under various humid conditions, and a stable output performance was observed even up to 60% relative humidity. Such a stable output performance is due to the hydrophobic nature of the device, and a large water contact angle of 141° is obtained. A real time application of the wearable WS₂QDs-PANI nanocomposite nanogenerator as a piezoelectric touch sensor was also demonstrated under various human body movements.