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

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.