ABSTRACT With the growing demand for flexible, portable and wearable energy sources, polymer/carbon nanotube composites have attracted growing interest for energy harvesting applications. In this study, we present the morphology, structure, and initial piezoelectric behavior of electrospun hybrid fibers comprising recycled expanded polystyrene (rEPS), neat polyvinylidene fluoride (PVDF), and functionalized carbon nanotubes ( f ‐CNTs). Various hybrid fibers, including rEPS/PVDF, rEPS/CNT, and rEPS/PVDF/CNT, were fabricated by optimizing the polymer solutions and operational conditions during electrospinning. Among the fibers, rEPS/CNT exhibited the highest output voltage of 0.39 V under a compressive force of 3.5 N, outperforming both rEPS/PVDF and rEPS/PVDF/CNT composite fibers. While the energy harvesting performance remains moderate, rEPS/CNT composite fibers demonstrated the potential for further development as flexible nanogenerators (NGs). These preliminary results suggest that rEPS‐based fibers, particularly those incorporating f ‐CNTs, may offer a pathway toward the fabrication of lightweight, flexible, and self‐powered devices, although additional work is required to enhance their electrical output and device stability.

Recent advances in polysaccharide-derived piezoelectric nanogenerators for wound healing application.

The rapid evolution of solar panels towards greener energy has paved the way for eco-friendly renewable energy generation. However, the effective management of disposed solar cells is an important factor to consider in reducing adverse environmental and health consequences. Hence, ‎the novel based Triboelectric Nano generators are fabricated from waste solar cells and waste chocolate wrappers. The TENG harnesses ‎frictional energy from the contact between the materials, converting it into useful electrical power. This innovative system promotes the ‎efficient utilization of discarded resources, contributing to both renewable energy generation and waste reduction. As a result, the current work offers a realistic technique for gathering electricity and represents a major step in mitigating the difficulties associated with disposing of solar cell waste. The ‎output voltage generation by the TENG is predicted using various Machine learning algorithms. The predictive model performance is also ‎analyzed through various metrics such as Root Mean Square Error (RMSE) and Mean Absolute Percentage Error (MAPE)‎.

Instantaneous Piezoelectric Nanogenerator for Pacemaker Applications.

Spinal cord injury (SCI) is a severe neurological disease, often accompanied by impaired lower limb motor function and muscle atrophy. Epidural electrical stimulation (EES) has been demonstrated promising for SCI therapy in ways of rehabilitation by facilitating the recovery of lower limb motor abilities. However, EES necessitates a considerable consumption of electrical energy and exhibits large individual differences in treatment. Nanogenerators (NGs) based on a novel power generation technology, are capable of transforming mechanical energy into electrical power. This mechanic‐driven electrical stimulation has been reported effective in several types of neuromodulations, but not in EES to enable SCI rehabilitation. This study explores the efficacy of a hybrid‐NG (H‐NG) to elicit hindlimb locomotion in rats via EES on the spinal cord, in comparison with a commercial stimulus generator (SG). The results reveal that H‐NG can activate the spinal cord and induce hindlimb locomotion with much lower electrical parameters and much smaller individual differences than SG. In addition, benefiting from the miniature size of the H‐NG, an implantable EES system is constructed in vivo, enabling a self‐driven and rational‐controlled EES pattern. The proposed H‐NG‐based EES system provides a new strategy for optimized and personalized treatment for SCI patients.

Biomechanical-to-electrical energy conversion technology rapidly developed with the emergence of nanogenerators (NGs) in 2006, which proves promising in distributed energy management for the Internet of Things, self-powered sensing, and human-computer interaction. Recently, researchers have increasingly integrated inorganic dielectric materials (IDMs) and micro-/nanoarchitectures into various types of NGs (i.e., triboelectric, piezoelectric, and flexoelectric NGs). This strategy significantly enhances the electrical performance, enabling near-theoretical energy harvesting capability and precise multiple physiological information detection. However, because micro-/nanoarchitectured IDMs function differently in each type of NG, numerous studies have focused on a single NG type and lack a unified perspective on their role across all types of biomechanical energy NGs. In this review, from an overall theoretical root of NGs, the performance enhancement mechanisms and effects of designs of IDMs coupling micro-/nanoarchitectures of various kinds of biomechanical energy NGs are systematically summarized. Next, advanced applications in human energy scavenging and physiological signal sensing are delved into. Finally, challenges and rational guidelines for designing future devices are discussed. This work provides researchers with in-depth insight into the development of high-performance personalized high-entropy power supplies and sensor networks via biomechanical-to-electrical energy conversion technologies based on IDMs coupling micro-/nanoarchitectures.

Great carbon nano materials based composites for electronic skin: Intelligent sensing, and self-powered nano generators

Metal–organic frameworks (MOFs) are known for their high porosity and stability, making them ideal for various applications, including energy harvesting. A simple synthesis method was used to synthesize zinc‐based metal–organic frameworks (Zn‐MOFs) and introduce them into an ultra‐stretchable Ecoflex polymer as functional fillers. We developed triboelectric nano generator (TENG) devices using Ecoflex, both pristine and modified with different Zn‐MOF concentrations, to evaluate their performance. The output voltage, current, and instantaneous power of Zn‐MOF‐modified Ecoflex TENG devices were 3, 4, and 5 times higher than pristine Ecoflex TENGs. This improvement is due to Zn‐MOF's large surface area, porous structure, charge trapping sites, improved surface roughness, and electron cloud conduction. The improved TENG device achieved 36 mW of maximum power and 40 mW m−2 power density. The Flexible TENG device powered LEDs and stored energy in capacitors by converting mechanical energy into electrical energy. We integrated flexible TENG device into cardiac patients' shoes to monitor running speeds and identify dangerous velocities using wireless IoT cloud monitoring. Real‐time notifications and wireless data transmission to families and emergency personnel allowed immediate assistance.

Harnessing energy from low-frequency and low-amplitude vibrating sources using triboelectric nano generator

The use of piezoelectric devices as wireless electrical stimulators is an emerging research topic. In this study, piezoelectric microdevices, consisting of ZnO nanosheets (NSs) functioning as piezoelectric nanogenerators (NGs) grown on top of silicon microparticles, to electrically stimulate cell are designed. The morphology of the ZnO NSs is optimized by tuning the thickness of the aluminum nitride (AlN) catalyst layer and adjusting the growth duration. ZnO NSs grown on thinner AlN layers (≤ 200 nm) and subjected to 9 h of hydrothermal growth exhibit the most suitable characteristics for cell stimulation, balancing crystal size, and electric field generation. The generation of a local electric field capable of exciting osteoblast cells is inferred from finite element simulations and intracellular calcium influx measurements. The internalization rate of silicon microdevices of varying sizes (3 × 3, 6 × 10, 12 × 18 µm2) by osteosarcoma (Saos‐2) and primary human osteoblast (hOB) cells is assessed. The results show that smaller devices have higher internalization rates, particularly in tumoral Saos‐2 cells, while primary cells exhibit minimal internalization (< 10%) across all particle sizes. This study presents an optimized piezoelectric microdevice, based on a scalable and customizable fabrication process, for minimally invasive bioelectronic applications, offering accurate electrical cell stimulation while minimizing unwanted internalization.

Piezoelectric polymer textiles offer distinct advantages in the fabrication of wearable nanogenerators (NGs). One effective strategy to enhance the output capacity of NGs is to modulate the piezoelectric performance of the textiles. This paper focuses on further improving the piezoelectric properties of nylon-11,11 textiles through post-drawing and annealing treatments. We elucidate the evolution of morphology and the ferroelectric phase in the submicron/nanoscale fibers during post processing as well as the corresponding changes in performance. The drawing process primarily enhances the orientation of the crystalline phase and reduces the fiber diameter, while the annealing process more effectively promotes the crystal size and crystallinity. Afterward, we propose an optimal postdrawing and annealing assisted-electrostatic spinning process. Under the synergistic effects of these post-treatments, the remanent polarization (Pr) of nylon-11,11 textile increased to 4.7 times that of the untreated textile, resulting in amplified piezoelectric outputs. The output voltage, current, and power density of the prepared PENG reached 21.5 V, 800 nA, and 1.88 mW·m-2 (80 MΩ), respectively. Notably, at pressures exceeding 8 kPa, the mechano-voltage and current sensitivity reached as high as 266 mV/kPa and 13.99 nA/kPa, respectively, which is extraordinary compared to other piezoelectric NGs and comparable to the performance of nylon-based triboelectric NGs. Furthermore, we investigated the potential application of the prepared PENG in biomechanical energy harvesting and human movement monitoring. Experiments demonstrated its effectiveness in powering light bulbs, tracking walking status, and monitoring finger/hand/wrist gestures.

Gas sensors are now widely employed in many industries due to the rapid speed of industrialization and the growth of the Internet of Things. However, the wearability and mobility of traditional gas sensors are limited by their high reliance on external power sources. Nanogenerators (NGs) can compensate for their power source limitations when paired with gas sensors by transforming the environment's widely dispersed low-frequency energy into electrical energy, allowing for self-powered gas detection. The paper thoroughly examines the advancements made in the field of NG-based self-powered gas sensor research in recent years. A systematic description is given of the two main types of NG-based self-powered gas sensors. Lastly, the evolution of sensor use in a few typical gas sensing applications is highlighted, and the field's future development trend is anticipated.

Large-area sensing devices open up great potential to trigger continuous self-powering, multifunctional sensors with responses to multiple stimuli. Herein, we report a self-powered flexible hybrid piezo- and pyro-electric nanogenerator (NG) based on Te-reinforced poly(vinylidene fluoride) (PVDF) electrospun nanofibers. It is tested to generate electricity from waste mechanical and thermal energies at room temperature. An electroactive phase (∼94%) is built in along the interface (an electrified jet) of dipoles poled perpendicular to the PVDF backbone '-C-C-' chains. As a proof-of-concept, the fabricated NG generates remarkable electricity, reaching a power density of 4.2 μW cm-2 under periodic mechanical stimulation, showcasing its potential for the efficient conversion of ambient mechanical energy into electricity. The intrinsic photothermal heat-localization effect of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as an organic electrode enhances the pyroelectric response, yielding a pyroelectric coefficient of 40 μC m-2 K-1 (which is 4 times higher than that of the undoped fibers), making it capable of detecting low thermal oscillations. Therefore, it has the potential to monitor physiological conditions and body temperature, making it suitable for remote infectious disease surveillance.

Flexible piezoelectric Nano Generator based on PVDF

Diverse forms of mechanical energy are available in environmental routine activities. These energy forms can be harvested, measured and converted to produce electricity at nanogenerator (NG) and micro-scale levels based on the phenomenon of triboelectrification. These motivate this work to develop a self-powered sensing device to detect and monitor static and dynamic processes associated with mechanical activities. The significance is to study the output characteristics of freestanding mode triboelectric nanogenerator (TENG) with multiple units of metal and dielectric electrodes. The integrated modeling environment of COMSOL Multiphysics software was employed for the simulation study of the proposed TENG. The system output responses considered for analysis includes, open circuit electric potential and short circuit surface charge density. For the open circuit, the electric potential was achieved at maximum value of 10kV, while for short circuit surface charge density, the electric potential was achieved at maximum value of 27 Cm-2. The study results revealed that the input parameter of contact displacement of electrodes is proportional to the output electrical potential of the system. Hence, the efficiency of TENG can be deployed for energy harvesting and sensing of mechanical variables.

Inspired by camouflage-colored organisms, the development of bio-camouflage systems using electrochromic (EC) technology has gained significant interest. However, existing EC systems struggle with achieving a wide color gamut, noniridescent colors, and self-sustainability. Herein, a self-sustainable color-adaptive bio-camouflage system integrating EC and nanogenerator (NG) technologies, enabling environmental color adaptation, and thermal regulation without an external power source is proposed. The system is based on a zinc-anode EC device (ZECD) with an asymmetric structure, incorporating flexible tungsten oxide and vanadium oxide electrodes. During the EC process, tungsten oxide shifts between blue and transparent, allowing near-infrared thermal modulation, while the vanadium oxide transitions from yellow to transparent. This design enables reversible near-infrared modulation and noniridescent color conversion among black, blue, green, yellow, and transparent. For the self-sustainability of the system, an electromagnetic and triboelectric hybrid NG that collects biomechanical energy is developed. In a typical driven cycle, the integrated system transitions colors and achieves significant near-infrared spectral modulation, demonstrating environmental adaptability and thermal regulation. Experiments on human skin and simulated chameleon color changes further confirm the system's effectiveness. This work highlights the potential of integrating EC and NG technologies to advance color-adaptive camouflage systems, opening new an avenue for bio-camouflage design.

In this review, we introduce recently developed plasma-based approaches for depositing and treating piezoelectric nanoparticles (NPs) and piezoelectric polymer films for nanogenerator (NG) and sensor applications. We also present the properties and an overview of recently synthesized or modified piezoelectric materials on piezoelectric polymers to highlight the existing challenges and future directions of plasma methods under vacuum, low pressure, and ambient air conditions. The various plasma processes involved in piezoelectric NGs and sensors, including plasma-based vapor deposition, dielectric barrier discharge, and surface modification, are introduced and summarized for controlling various surface properties (etching, roughening, crosslinking, functionalization, and crystallinity).

Flexible hybrid nanogenerator coupling of triboelectric and photovoltaic effects based on fluoride dielectric regulation for energy harvesting

Dual regulation of osteosarcoma hypoxia microenvironment by a bioinspired oxygen nanogenerator for precise single-laser synergistic photodynamic/photothermal/induced antitumor immunity therapy

A smart mRNA-initiated DNAzyme nanogenerator for precise imaging and gene therapy in vivo