Abhinav Mahapatra

The rapid growth of wearable electronics, smart textiles, and the Internet of Things (IoT) has increased the demand for sustainable, self‐powered energy solutions. Textile‐based triboelectric nanogenerators (T‐TENGs) have emerged as a promising technology by combining efficient mechanical energy harvesting with the flexibility, breathability, stretchability, washability, and wearability of textiles. This review provides a comprehensive overview of recent advances in T‐TENGs, covering the complete design hierarchy from fundamental mechanisms to wearable applications. The operating principles of alternating‐current and emerging direct‐current TENGs, including contact electrification, electrostatic induction, electrostatic breakdown, and tribovoltaic effects, are discussed. Recent progress in triboelectric material engineering, fiber and yarn design, and textile architectures—including woven, knitted, braided, embroidered, multilayer, and 3D structures—is systematically reviewed with emphasis on performance enhancement and scalability. Applications in biomechanical sensing, wearable healthcare, human–machine interaction, smart textiles, and self‐powered wearable systems are summarized, highlighting the distinction between self‐powered sensing and fully autonomous wearable platforms. Finally, key challenges, including low current output, environmental stability, washability, durability, scalable manufacturing, performance standardization, and commercialization, are critically analyzed, and future research directions toward intelligent, fully autonomous, and commercially viable self‐powered wearable systems are outlined.

Scalable and highly efficient electrocatalysts are essential for hydrogen production via the hydrogen evolution reaction (HER). In this study, we demonstrate a simple CO ₂ laser‐scribing method to prepare a new laser‐induced graphene (LIG)‐WS ₂ hybrid electrocatalyst, where liquid‐phase‐exfoliated WS ₂ nanosheets are embedded into a porous graphene network. Structural and spectroscopic characterizations confirm the few‐layer WS ₂ , defective LIG, and the interfacial coupling without any oxide formation. The LIG‐WS ₂ hybrid demonstrates significantly improved HER activity in seawater, alkaline seawater, and alkaline media, especially in 1M KOH, with a low overpotential of 163 mV at 10 mA cm ^{− 2} , a small Tafel slope of 63 mV dec ^{− 1} , a lower charge‐transfer resistance, and a higher mass activity (13.26 A/g) than the pristine components. This exceptional performance is attributed to the synergistic effects of rapid electron transport through LIG and the efficient hydrogen adsorption ability of WS ₂ edge sites. This study demonstrates CO ₂ laser scribing as a scalable platform to develop high‐performance graphene‐based HER electrocatalysts in alkaline and seawater environments.

Single-electrode triboelectric nanogenerators (STENGs) are promising candidates for biomechanical energy harvesting and self-powered sensing due to their simple structure and compatibility with wearable systems. However, their performance is often limited by the intrinsic tribonegativity of polymer friction layers. In this study, we report a facile surface chemistry approach to enhance the triboelectric performance of polydimethylsiloxane (PDMS) by fluorinated silane functionalization. PDMS films spin-coated on ITO/PET substrates were surface-functionalized using 1H, 1H, 2H, 2H-perfluorooctyl-trichloroethoxysilane (FOTES), introducing fluorine-rich –CF2 and –CF3 groups at the outermost surface. X-ray photoelectron spectroscopy confirmed successful fluorination, while Kelvin probe force microscopy revealed a significant reduction in surface potential, indicating enhanced electron-accepting capability and increased tribonegativity. As a result, the FOTES-functionalized PDMS STENG exhibited a substantial improvement in output performance, with the open-circuit voltage and short-circuit current increasing from ∼91.5 and ∼10 to ∼390 V and ∼65 μA, respectively, under hand-tapping conditions. The enhanced performance was further validated under controlled excitation (30 N, 4 Hz). The device demonstrated practical energy-harvesting capability through efficient rectification, capacitor charging, and instantaneous lighting of 240 commercial LEDs, achieving a maximum power density of 5.53 mW cm−2. In addition, the STENG functioned as a self-powered biomechanical motion sensor, capable of distinguishing different human motions such as clapping, clicking, and hammering based on distinct voltage signatures. This study demonstrates that fluorinated surface functionalization is an effective and scalable strategy to enhance triboelectric performance without increasing device complexity, offering strong potential for wearable energy harvesting and self-powered sensing applications.

Synergistic integration of Al-doped ZnO, a SiO ₂ electron-blocking interlayer, and a MoS ₂ –PDMS nanocomposite results in a flexible high-output triboelectric nanogenerator capable of lighting 400 LEDs and maintaining long-term operational stability.

In recent years, ZnO based piezoelectric nanogenerators (PENGs) have gained considerable attention for vibration energy harvesting and self-powered applications. This study reports the development and optimization of flexible ZnO based PENGs (ITO/ZnO/Al) through vanadium (V) doping and the insertion of a SiO ₂ interlayer. When V concentration was increased to 3% the open-circuit voltage and short-circuit current of the PENG increased from ~0.9 V/0.1 μA to 2.2 V/0.3 μA. However, further increasing the V doping to 5% reduced the output to ~1.9 V/0.2 μA. X-ray photoelectron spectroscopy (XPS) analysis showed that at low to moderate V doping levels (1%-3%), the V ⁵⁺ /V ³⁺ ratio increases, leading to enhanced internal polarization and, consequently, an improved piezoelectric output performance. At higher V doping levels (5%), excess vanadium introduces structural defects in ZnO, increasing oxygen vacancies and thereby deteriorating the output performance of the PENG. A 100 nm SiO ₂ interlayer was inserted between the 3% V-doped ZnO (VZO) and the Al electrode which introduces a conduction band offset of ~6.4 eV as evaluated from band offset studies. This band offset effectively reduces the leakage current in VZO piezoelectric layer and enhanced the output to ~4.4 V/0.6 μA. The optimized PENG generated an instantaneous power density of ~0.1 μW/cm ² with normalized power density per unit force and frequency ~8.3 × 10 ^-4 μW·cm ² /(N·Hz) which was successfully powered commercial capacitors (1 μF to 10 μF), stopwatch LCD screen and LEDs. This work highlights the role of vanadium states, oxygen vacancies and SiO ₂ interlayer in tuning ZnO based PENG performance and demonstrates its potential for powering micro/nanoelectronic devices in self-powered applications.

ZnO based piezoelectric nanogenerators (PENG) hold immense potential for harvesting ambient vibrational mechanical energy into electrical energy, offering sustainable solutions in the field of self-powered sensors, wearable electronics, human–machine interactions etc. In this study, we have developed flexible ZnO-based PENGs by incorporating ZnO microparticles into PDMS matrix, with ZnO concentration ranging from 5 to 25 wt%. Among these, the PENG containing 15 wt% ZnO exhibited the best performance with an open-circuit output voltage/short-circuit current of ~ 42.4 V/2.4 µA. To further enhance the output performance of PENG, p-type NiO was interfaced with ZnO in a bulk hetero-junction geometry. The concentration of NiO was varied from 5 to 20 wt% with respect to ZnO and incorporated into the PDMS matrix to fabricate the PENGs. The PENG containing 10 wt% NiO exhibits the best performance with an open-circuit output voltage/short-circuit current of ~ 65 V/4.1 µA under loading conditions of 30 N and 4 Hz. The PENG exhibiting the best performance demonstrates a maximum instantaneous output power density ~ 37.9 µW/cm² across a load resistance of 20 MΩ under loading conditions of 30 N and 4 Hz, with a power density per unit force and Hertz of about ~ 0.32 µW/cm²·N·Hz. The enhanced output performance of the PENG is attributed to the reduction in free electron concentration, which suppresses the internal screening effect of the piezopotential. To assess the practical utility of the optimized PENG, we tested the powering capability by charging various commercial capacitors and used the stored energy to illuminate 10 LEDs and to power a stopwatch displays. This work not only presents a straightforward, cost-effective, and scalable technique for enhancing the output performance of ZnO-based PENGs but also sheds light on its underlying mechanism.

A self-powered UV sensor with high responsivity was developed by coupling ZnO based piezoelectric nanogenerator and photodetector for uninterrupted real-time monitoring of UV radiation. Unlike conventional UV photodetectors, our approach couples a ZnO based metal-semiconductor-metal photodetector as a variable load resistor with a flexible ZnO:PVDF piezoelectric nanogenerator through impedance matching to realize self-powering of photodetector. The as fabricated UV photodetector exhibits a dark resistance of approximately 55 MΩ and change of resistance from 12 to 2 MΩ in response to UV illumination ranging from 1.5 to 14.5 mW/cm2. Under UV exposure of 1.5 mW/cm2, the output voltage of self-powered UV sensor drops from ∼14.6 V (dark) to ∼3.88 V. With increasing UV intensity from 1.5 to 14.5 mW/cm2, the output voltage gradually decreases from ∼3.88 to ∼1.04 V due to reduced ZnO photodetector resistance. This self-powered UV sensor exhibits excellent performance with a sensitivity of ∼93%, a voltage responsivity of 7.14 V (mW−1 cm−2), a response time of 0.67 s, and a recovery time of 4 s, which are better than the previous reports. The environmentally stable and biocompatible nature of ZnO based system makes it a promising candidate for self-powered real time ultraviolet remote sensing applications.

In the past decade resistance-based memory devices, or the resistive random access memory Devices (RRAM) have emerged as a potential candidate for multi-state memory storage and non-conventional computing applications. Reports on conduction quantization (QC) have added an interesting layer to the utility of these RRAM devices for ultra-dense memory and neuromorphic computing applications due to the occurrence of integral and half-integral conduction (resistive) states. Since the first reports of QC phenomena in RRAM devices, there have been detailed studies on the nature of the conducting filaments, switching mechanisms, and tunability of the QC states, but there exists a scarcity of studies exploring controllability of QC phenomena in scalable device geometries. In this work, we report compliance current controlled tunable QC phenomena in crossbar RRAM cells based on electrochemical metallization switching mechanism. The devices exhibited robust bipolar resistive switching, with well separated high and low resistance states.  The magnitude and number of the QC states were found to increase from ~2.5 to 3.5 and from 4 to 6, respectively as the IC increased from 50 to 200μA. The Cu/Ta2O5/Pt device structure was chosen to strategically govern the metallic nature of the conduction filament (CF) formation, which helped postulating factors contributing to the tunability of the states via compliance current. We report the lateral dimension variability as the main factor governing the magnitude and number of quantized steps observed in RRAM devices, where we also discuss a numerical method to approximate the diameter of the CFs. The increase in number and magnitude of QC steps with IC was explained considering the fact that thicker CF obtained at higher ICC , when undergoes a gradual rupture during reset process, results in larger number of QC steps compared to a thinner CF.