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Self-powered sensor development is moving towards miniaturization and requires a suitable power source for its operation. The piezoelectric nanogenerator (PENG) is a potential candidate to act as a partial solution to suppress the burgeoning energy demand. The present work is focused on the development of the PENG based on flexible polymer-ceramic composite films. The X-ray spectra suggest that the BTO particles have tetragonal symmetry and the PVDF-BTO composite films (CF) have a mixed phase. The dielectric constant increases with the introduction of the particles in the PVDF polymer and the loss of the CF is much less for all compositions. The BTO particles have a wide structural diversity and are lead-free, which can be further employed to make a CF. An attempt was made to design a robust, scalable, and cost-effective piezoelectric nanogenerator based on the PVDF-BTO CFs. The solvent casting route was a facile approach, with respect to spin coating, electrospinning, or sonication routes. The introduction of the BTO particles into PVDF enhanced the dielectric constant and polarization of the composite film. Furthermore, the single-layered device output could be increased by strategies such as internal polarization amplification, which was confirmed with the help of the polarization-electric field loop of the PVDF-BTO composite film. The piezoelectric nanogenerator with 10 wt% BTO-PVDF CF gives a high electrical output of voltage 7.2 V, current 38 nA, and power density of 0.8 μW/cm2 at 100 MΩ. Finally, the energy harvesting using the fabricated PENG is done by various actives like coin dropping, under air blowing, and finger tapping. Finally, low-power electronics such as calculator is successfully powered by charging a 10 μF capacitor using the PENG device.

This study aims to explore usability issues of watch‐type wearable devices and to suggest guidelines for improved operation of smartwatches. To do so, we conducted a series of surveys, interviews, and task performance experiments. Thirty smartwatch users from ages 20 to 43 years were recruited. Users’ experiences of smartwatches were collected via a weeklong, online‐based diary study, which consisted of various tasks to be completed while smartwatches were in use. Our study assessed usability problems associated with those tasks, concurrent tasks conducted while interacting with smartwatches, pain points/discomfort that users had while interacting with their devices, and requirements/requests of the smartwatch users. During the week of tracking, participants were asked to complete the usability evaluation three times a day using usability principles we designed for the study: information display, control, learnability, interoperability, and preference. In addition, task performance tests were conducted for the tasks most frequently conducted on touch‐based displays: number entry, swiping, and scrolling. Specific usability issues of smartwatches were identified and summarized for each usability principle by triangulating survey, interview, and task performance evaluation results. Based on the insights from the results of the study, we conclude by suggesting guidelines for further enhancing users’ experience of future smartwatches.

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The piezoelectric nanogenerator (PENG) depends upon the piezoelectric material for the conversion of mechanical stress into useful electrical energy. Development of piezoelectric material compositions starting from ceramic oxides, polymer, and...