In this contribution, we reply to comments made by Tkach et al. in our publication J. Materiomics 2023; 9:609. The main interest of our work is to synthesize a lead-free material, SrTi₂O₅ (STO), and then utilize it in the formation of composites and finally design the piezoelectric nanogenerator (PENG) for self-powered sensor applications. The authors have observed the presence of piezoelectric voltage and current output from the PENG. The authors humbly indicate that the PENG devices were poled using a DC poling setup as conditions mentioned in J. Materiomics 2023; 9:609 (Panda et al., 2023) [1]. The doping of STO into the PDMS increased from 2% to 20% (in mass). In this process, the piezoelectric output of the PENG device was observed to be highest for 15% (in mass) STO-PDMS composite. Besides, we agree with the comment raised by Tkach et al., and further we have addressed the issues in a step-by-step response as follows.

Morphotropic phase boundary (MPB)-based ceramics are excellent for energy harvesting due to their enhanced physical properties at phase boundaries, broad operating temperature range, and ability to customize properties for efficient conversion of mechanical energy into electrical energy. In this work, Bi_1-xNa_xFe_1-xNb_xO₃ (x = 0.20, 0.30, 0.32 and 0.40, BNFNO abbreviation) based ceramics were synthesized using a solid-state route and blended with Polydimethylsiloxane (PDMS) to achieve flexible composites. Various material characterization and energy harvesting were performed by designing a hybrid piezoelectric (PENG)-triboelectric (TENG) device. The voltage and current of PENG, TENG, and hybrid bearing same device area (2 cm × 2 cm) were recorded as 11 V/0.3 μA; 60 V/0.7 μA; 110 V/2.2 μA. The strategies for enhancing the output performance of the hybrid device were evaluated, such as increased surface area (creating micro-roughness and porous morphology) and increasing electrode size and multi-layer hybrid device formation. The self-powered acceleration monitoring was demonstrated using the hybrid device. Further, the low-frequency-based wave energy is converted into electrical energy, confirming the usage of hybrid PENG-TENG devices as a base for battery-free sensors and blue energy harvesting.

Lead-free piezoelectric ceramic is a promising material for energy harvesters, as they have superior electromechanical, ferroelectric, and piezoelectric properties. In addition, piezoelectric ceramics can be blended with polymer to achieve high-flexibility polymer-ceramic composites, providing mechanical robustness and stability. In this context, a new lead-free ferroelectric material, having the chemical formula SrTi₂O₅ (STO), was synthesized using a high-temperature solid-state reaction. Detailed analyses of the structural, morphological, and electrical properties of the synthesized material were performed. STO crystallizes with orthorhombic symmetry and space group of Cmm2. The frequency and temperature-dependent dielectric parameters were evaluated, and impedance spectroscopy shed light on the charge dynamics. The PDMS-STO composites at different mass fraction of the STO were prepared using a solvent casting route, and a corresponding piezoelectric nanogenerator (PENG) was developed. The electrical output of the different PENG by varying massfractions of STO in PDMS and varying force were investigated. The 15% (in mass) PENG device delivered the highest peak-to-peak voltage, current, and power density of 25 V, 92 nA, and 0.64 μW @ 500 MΩ, respectively. The biomechanical energy harvesting using the PENG device by daily human motions, bending of the device, and attaching the device to laboratory equipment was demonstrated. Later the PENG device was attached to the human throat region, and snoring signals were recorded. A classification model was designed employing the convolutional neural network (CNN) model. Efforts have been laid to differentiate between normal and abnormal snores, which could help the patient with screening and early disease detection, contributing to self-powered healthcare applications.