The need for technological innovation in competitive sports is crucial for self-monitoring and smart decision making. In this work, we demonstrate how intelligent sports and smart decision making can be achieved in cricket and boxing using lithium-modified zinc titanium oxide (LZTO) nanofibers based on piezoelectric nanogenerators (PENGs) and triboelectric nanogenerators (TENGs). Zinc titanium oxide (ZTO) nanofibers synthesized using electrospinning followed by a calcination technique are modified with lithium to increase the output of the nanogenerator. An optimized PENG is fabricated using 25 wt % loading of LZTO (d 33 = 214 pm/V) in a poly(vinylidene fluoride) (PVDF) matrix as a double-layered structure and yields an open-circuit voltage (V oc) of 35 V and a short-circuit current (I sc) of 1.6 μA by manual tapping. To fabricate the TENG, Kapton and LZTO are used as negative and positive tribolayers, while Cu and adhesive polymer tape are used as the electrode and spacer, respectively. Furthermore, a hybrid nanogenerator (HNG) is fabricated by combining the PENG and TENG to produce a rectified voltage, current, and power density of up to 75 V, 3.2 μA, and 240 μW/cm2, respectively. These HNGs are integrated with a punching bag and demonstrated to differentiate among the six types of punches in boxing. Furthermore, PENGs are used in cricket to monitor the number of balls middled on the bat during practice and the contact of the ball with the bat and stumps for smart decision making. All kinds of lab-scale testing are done for these applications, which pave a way for exploring the frontiers in nanogenerator applications in sports as maintenance-free and self-powered sensing technology.

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Recent advancements in printing technologies have led to new fabrication techniques for the development of various flexible, compact, wearable, and portable energy harvesters and self-powered devices. In particular, the three-dimensional printing (3DP) technology for a nanogenerator has become advantageous due to its low cost, simplicity, and high precision in fabricating complicated structures. Therefore, we report a 3DP-based photoinduced triboelectric nanogenerator (PTNG) fabrication, a hybrid version of a conventional triboelectric nanogenerator. Here, a 3D printed poly­(vinyl alcohol) (PVA) nanocomposite hydrogel (3DPH) with photoactive SnS2/SnS nanoflakes is used as a tribo-positive material and copper foil as a tribo-negative material for PTNG application. Under light illumination, the as-fabricated PTNG with an optimized weight percentage of SnS2/SnS displays the open-circuit voltage (V oc) enhancement from 29 to 37.5 V and short-circuit current (I sc) enhancement from 1.23 to 1.58 μA. In addition, the power density of the device is observed at 5.4 μW/cm2 under illumination conditions at the external load of 60 MΩ. This enhanced performance of the as-fabricated PTNG is attributed to the mutual coupling effect and improved interfacial interactions between the SnS2/SnS nanoflakes and PVA under the influence of light illumination, leading to a charge-trapping mechanism. The outstanding performance and stability of the as-fabricated PTNG surpassing all similar recent reports, establish it as an effective hybrid platform for constructing multifunctional self-powered devices.

With technological advancements in healthcare, the demand for wearable sensors to monitor human movements has become increasingly popular. However, the limited lifetime of the energy sources that power these devices remains a challenge. In this work, we report on a low-cost, flexible, and skin-conformal wearable piezoelectric nanogenerator (PENG) based on hydrothermally grown zinc ferrite nanoparticles, i.e., ZnFe 2 O 4 (ZFO nanoparticles), and poly-(dimethylsiloxane) (PDMS) composite as a self-powered sensor to monitor patients' activities. The FCC cubic spinel crystal structure of ZFO nanoparticles with Fd3̅ m space group is confirmed by X-ray spectroscopy (XRD) and Raman spectroscopy. The non-centrosymmetric structured ZFO nanoparticles exhibit exceptional piezo-properties, including a d 33 value of 333 pm/V obtained from the piezoresponse force microscopy (PFM) study, which is significantly higher than that of similar class of oxide-based piezoelectric materials. To fabricate the device, the ZFO nanoparticles and PDMS-based composite solution is spin coated on a Cu foil and sandwiched between a pair of Cu foils after drying it. The as-fabricated PENG with an optimized 5 wt % of ZFO nanoparticles exhibits an opencircuit voltage (V oc ) of 40 V and a short-circuit current (I sc ) of 0.6 μA upon finger tapping. Further, the PENG is used as a selfpowered sensor to monitor various human activities, including human gait, fall detection, and joint movement. The fabricated PENG demonstrates excellent stability with 95% voltage output retention after 60 days. The work demonstrated here has enormous potential in the healthcare sector, which involves patient rehabilitation for musculoskeletal abnormalities, leg injuries, and elderly assistance including geriatric rehabilitation, etc.