Self-powered wearable sensors exhibiting high sensitivity and flexibility have attracted widespread interest in the field of wearable electronics. Herein, a 3D printing technique was employed to fabricate a fully printed, flexible self-powered sensor with high piezoelectric performance. This printing technique is based on the hydrophobic surface-functionalized barium titanate (FD-BTO)/polyvinylidene fluoride (PVDF) composite film. To strengthen the interface bond between BTO and PVDF, the BTO nanoparticles were surface functionalized using hydrophobic 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTES). As a result, there was an increase in the content of the β-phase in the PFDTES modified BTO (FD-BTO) nanoparticle composite film. The 3D-printed self-powered sensor based on the optimum FD-BTO/PVDF composite film exhibited excellent sensitivity (61.6 mV kPa⁻¹) with a piezoelectric coefficient (d₃₃) of 69.1 pC/N, which is two-fold higher than that of the unfunctionalized BTO/PVDF counterpart. Additionally, the power sensor displayed excellent mechanical durability in the 20 000 cyclic force tests. In practice, the printed devices were used as a sports wearable device to monitor and analyze athlete motion, and a self-powered printed sensor array (5 × 5), which could effectively detect the pattern image of the external pressure input. The 3D-printed self-powered sensor demonstrated herein can contribute significantly to the applications and the development of printed electronic wearable devices.

Conductive MWCNT/PSS composites have been directly patterned via electrohydrodynamic printing for application as source/drain electrodes in organic field-effect transistors.

Nanogenerators are the backbone of self-powered systems and they have been explored for application in miniaturized biomedical devices, such as pacemakers. Piezoelectric nanogenerators (PENGs) have several advantages, including their high efficiency, low cost, and facile fabrication processes, which have made them one of the most promising nano power sources for converting mechanical energy into electrical energy. In this study, we review the recent major progress in the field of PENGs. Various approaches, such as morphology tuning, doping, and compositing active materials, which have been explored to improve the efficiency of PENGs, are discussed in depth. Major emphasis is given to material tailoring strategies and PENG fabrication approaches, such as 3D printing, and their applications in the biomedical field. Moreover, hybrid nanogenerators (HNG), which have evolved over the last few years, are discussed. Finally, the current key challenges and future directions in this field are presented.

Piezoelectric nanogenerators with excellent electromechanical coupling effects are in great demand for self-powered Internet-of-Things (IoT) devices. In this work, a novel solid–liquid nanocomposite-based piezoelectric nanogenerator (SL-PENG) with unprecedented properties was developed by employing 1H,1H,2H,2H-perfluorodecyltriethoxysilane (FDTS) droplets as liquid fillers. Through the combination of solvent selection and solvent evaporation protocols, highly deformable FDTS nanodroplets with a controllable droplet size were uniformly distributed in a polyvinylidene fluoride (PVDF) matrix, thereby improving the toughness of the polymer matrix. FDTS nanodroplets form strong intermolecular hydrogen bonds with PVDF chains to promote the transformation of α-phase to polar β-phase, while stabilizing the liquid phase that prevents FDTS nanodroplets from fracture and exudation to a polymer network. The synergistic contribution of the β-phase content and stress transfer ability significantly improves the output performance of SL-PENG, which is proved by the experimental results and COMSOL simulation. Remarkably, this SL-PENG generates a maximum peak-to-peak voltage and current as high as 62 V and 3.2 μA, respectively, corresponding to a power density of 35 μW cm⁻², which demonstrates remarkable superiority to other PENGs. Moreover, this SL-PENG is demonstrated as part of a monitoring device for the wireless sensor network, realizing the detection and response of physiological signals, and showing broad potential application prospects in the field of IoT.