The review, led by Premkumar Sharad Bhosale of the Daegu Gyeongbuk Institute of Science and Technology together with colleagues including Swati Panda, Dandugudumula Ramu, Sugato Hajra, Eunjoo Kim, and Hoe Joon Kim, surveys recent progress in TENG-based systems across machine fault detection, vibration monitoring, fluid flow control, air filtration, environmental monitoring, and mining safety. The authors emphasize that TENG devices are attractive for industrial deployment because they are self-powered, sustainable, inexpensive to fabricate, and compatible with flexible and even biodegradable materials. Their architecture can be tuned to many device layouts, and their electrical outputs integrate naturally with artificial intelligence and Internet of Things platforms, opening a path toward next-generation smart factories where sensors generate their own power and communicate autonomously.

At the heart of the technology is a simple physical mechanism. A typical TENG contains two dielectric layers with opposite triboelectric properties and two electrodes. When the layers come into contact, equal and opposite charges build at the surfaces. As the layers separate, electrons flow between the electrodes to balance the potential difference, producing a current. When the layers touch again, electrons flow in the reverse direction. This periodic motion generates an alternating electrical output that can be harvested, stored, and used to power small electronics. Researchers operate TENGs in four principal modes: contact-separation, single-electrode, lateral sliding, and freestanding. The freestanding mode is especially valuable for industrial use because the moving triboelectric layer never makes hard contact with the electrodes, minimizing surface wear and significantly extending device lifetime.

Among the most striking demonstrations is a vibrational TENG network developed by Li and colleagues for machine fault detection. The device stacked four contact-separation units with copper electrodes and polyethylene terephthalate triboelectric layers, producing an open-circuit voltage of 600 volts, a transferred charge of 0.85 microcoulombs, and a power density of 3.33 milliwatts per cubic meter. Connected through a power management module, microcontroller, and wireless transmitter, three self-powered vibration sensor nodes fed temperature and acceleration data into a support vector machine classifier, achieving 83.6 percent accuracy in detecting machine failures. The researchers point to smart factories, intelligent manufacturing, and continuous production monitoring as the most immediate applications for such networks.

Wind energy, often irregular and unpredictable inside industrial facilities, has also been harnessed. Zhang and co-workers built a turbine vent TENG integrating two freestanding-mode units and two contact-sliding-separation units on a conventional turbine vent. At a wind speed of seven meters per second, the device delivered 178.2 volts, a current of 38.2 microamperes, and 2.71 milliwatts of power, enough to light 120 green LEDs, charge a capacitor to drive a thermometer, and power a wireless alarm transmitter for early temperature warnings. In a complementary effort, Li and colleagues created a rotary wind-driven TENG that exploits the thermal response of nickel-titanium shape memory alloy to tune its contact area. At temperatures above 40 degrees Celsius, the alloy flattens and changes the electrical contact configuration, allowing the device to serve as a self-powered airflow temperature alarm for wind-cooled transformers, delivering an average power density of 140 milliwatts per square meter at twelve meters per second and a wind speed sensitivity of 0.526 microamps per meter per second.

Fluid control represents another frontier. Wang and colleagues developed a flapping-film TENG in which a soft fluorinated ethylene propylene film flutters between copper electrodes as air passes through a nozzle chamber, generating up to 32 volts and 2 microamps. Paired with an Arduino microcomputer, stepper motor, and blower, the system sensed and actively regulated airflow, with smoke visualization experiments at a Reynolds number of 8000 confirming precise control over flow fields. The researchers see direct applications in air conditioning, refrigeration, and production processes where real-time flow management matters. Meanwhile, Kisomi and colleagues applied contact-separation TENGs to air filtration, building industrial filters and face masks from polypropylene-polyurethane pairs that generated 10 to 20 kilovolts under airflow velocities between 1 and 5 centimeters per second. The electrostatic charging captured particles as small as PM0.1 with removal efficiencies reaching 99 percent at low airflow velocities, offering self-powered protection against industrial particulate pollution.

Vibration monitoring, a cornerstone of predictive maintenance, has been advanced by Jaurker and colleagues, who used laser micro-texturing on fluorinated ethylene propylene and aluminum layers to build a TENG producing 794 volts, 44 microamps, and a power density of 2371.6 microwatts per square centimeter. Mounted with an energy harvesting module charging a small battery, the device powered a Wi-Fi microcontroller that wirelessly transmitted vibration signatures to smart devices, instantly registering when a shaker turned on and off. For broader environmental surveillance, Zhang and co-workers introduced a pulsed TENG architecture that increases internal capacitance through an external capacitor, enhancing charge density while limiting open-circuit voltage. Coupled with a power management circuit and an LTC3588 converter, the platform periodically measured light intensity, temperature, humidity, and atmospheric pressure, transmitting data at intervals of seven minutes and thirty-five seconds. In mining, Liu and colleagues reported a triboelectric self-powered sensing platform in Nature Communications that detected wind speeds as low as 0.32 meters per second using a 3D-printed turbine with PTFE electret and conformal spiral electrodes, outperforming a commercial hot-wire anemometer in signal consistency over three months of field deployment, though cycle times lengthened from 64.9 to 196 seconds as the FEP and copper components degraded.

Despite these successes, the review is candid about the obstacles standing between laboratory prototypes and industrial reality. TENGs still suffer from relatively low power density, and their pulsed alternating output demands sophisticated rectification, storage, and regulation circuits to deliver stable direct-current power. Conventional polymers such as PTFE, PDMS, and Kapton generate strong triboelectric signals but wear down, degrade chemically, and lose charge under high pressure, temperature swings, oil contamination, and corrosive conditions. Humidity and thermal activity promote charge trapping and dissipation, and most durability studies have been confined to controlled laboratory settings rather than the harsh environments where these devices must ultimately survive. The authors call for scalable, low-cost fabrication routes such as soft lithography, laser ablation, roll-to-roll printing, and spray coating to produce industrial-grade devices that combine high output with mechanical robustness, alongside standardized evaluation benchmarks for performance, durability, and environmental resistance.

The path forward, the researchers argue, lies in hybridization and smarter materials. Combining TENGs with piezoelectric, electromagnetic, or photovoltaic harvesters could stabilize energy supply across dynamic industrial conditions, while biodegradable polymers such as silk fibroin, chitosan, polylactic acid, and polycaprolactone, reinforced with carbon nanomaterials, MXenes, or liquid-metal droplets, could raise charge density without sacrificing sustainability. Self-healing elastomers with dynamic covalent or supramolecular bonds promise autonomous recovery from mechanical damage, extending device lifetimes. Machine learning and artificial intelligence are expected to handle adaptive signal processing, predictive energy optimization, and autonomous fault diagnosis, while additive manufacturing and 3D and 4D printing could embed TENGs directly into robotic joints, machinery surfaces, and structural components. If these interdisciplinary threads converge, the authors conclude, triboelectric nanogenerators could become the self-sustaining nervous system of Industry 4.0, sensing, powering, and protecting the factories of the future without drawing a single external watt.

Subject of Research: Triboelectric nanogenerators for self-powered smart industrial sensing applications

Article Title: Triboelectric nanogenerators for smart industrial sensing applications

Article References: Bhosale, P. S., Panda, S., Ramu, D., Hajra, S., Kaja, K. R., Belal, M., Kim, E., & Kim, H. J. (2025). Triboelectric nanogenerators for smart industrial sensing applications. Advances in Industrial and Engineering Chemistry, 1(1), Article 40. https://doi.org/10.1007/s44405-025-00040-x

Image Credits: AI Generated

DOI: 10.1007/s44405-025-00040-x

Keywords: triboelectric nanogenerator, self-powered sensors, smart factory, energy harvesting, industrial IoT, vibration monitoring, machine fault detection, air filtration, power management, mining safety, Industry 4.0, nanogenerators

The performance of a filtering facepiece respirator is judged by two competing quantities: filtration efficiency, the fraction of incident aerosol particles it captures, and pressure drop, the resistance the filter poses to airflow. The NIOSH N95 standard, comparable to FFP2 in Europe and KN95 in China, requires filtration efficiency above 95 percent for a specified sodium chloride challenge aerosol, along with pressure drops below 245.2 pascals for exhalation and 343.2 pascals for inhalation at a flow rate of 85 liters per minute. The tension between these requirements is captured by the quality factor, defined as the negative logarithm of penetration divided by pressure drop; a higher quality factor means a filter collects more particles while breathing stays easier. Conventional N95s achieve their numbers with meltblown polypropylene fibers one to ten micrometers in diameter, made effective by embedded electrostatic charges that boost particle capture beyond what the fiber geometry alone could deliver.

That electrostatic crutch, the authors note, is also the conventional respirator’s Achilles heel. Surface charges decay with time, heat, moisture and liquid exposure, which is why manufacturers recommend limited shelf lives and limited periods of use. During the pandemic, testing of pristine commercial N95 and KN95 respirators revealed wide variability in performance, often falling below specification, because charge application and retention during production and distribution were inconsistent. And because polypropylene is not environmentally degradable, every retired respirator adds to the accumulating tide of plastic waste. Electrospun nanofiber filters offer a way out: their fibers are roughly an order of magnitude smaller than meltblown fibers, and that alone provides a favorable tradeoff between capture efficiency and air resistance, enough to reach N95 targets purely through mechanical filtration mechanisms such as diffusion and interception.

The MIT team chose poly(ε-caprolactone), or PCL, as their polymer, a synthetic polyester long used in biomedical applications and generally considered biocompatible. Previous studies have shown PCL degrades faster in soil and compost than other degradable polyesters such as polylactic acid, polyhydroxybutyrate and polybutylene succinate, and it also breaks down in natural aquatic environments. Earlier work had produced electrospun PCL air filters, but none had been specifically designed or tested against NIOSH N95 performance targets. Equally important was the choice of solvent. The researchers electrospun their fibers from a one-to-one mixture of acetic acid and formic acid, both classified by the FDA as biologically benign Class 3 solvents and rated favorably by green-chemistry solvent guides, in contrast to the dimethylformamide and dichloromethane common in the electrospinning literature. Because formic acid contains water that can catalyze hydrolysis of the polymer, the team added it to the solution only minutes before spinning, a trick that kept the process stable for hours and could be adapted to continuous manufacturing with inline mixing.

By tuning the polymer concentration of the spinning solution from 6 to 14 percent by weight, the researchers produced smooth, mostly bead-free fiber mats with average diameters spanning 60 to 300 nanometers. They then measured filtration efficiency and pressure drop for each mat across a range of basis weights, controlled simply by spinning time. Plotting the negative logarithm of penetration against pressure drop revealed a striking regularity: each set of filters fell on a straight line through the origin, the slope of which is the quality factor. This graphical construction doubles as a design tool. Choosing the fiber diameter and solidity sets the slope of the line, while adjusting basis weight moves the design along it, and a filter meets N95 requirements whenever its line passes through the target region defined by the efficiency and pressure-drop limits. All but the thickest-fiber media, spun from 14 percent solutions, crossed the target region, and every set met the less stringent inhalation limit.

The data showed a steep rise in quality factor for fibers thinner than 100 nanometers, consistent with purely mechanical filtration. Smaller fibers also shifted the most penetrating particle size downward, from just under 80 nanometers for the largest fibers studied to around 60 nanometers for the smallest, and because count-based measurements weight the smallest, hardest-to-capture particles equally, media achieving 95 percent efficiency by count are expected to meet or exceed that threshold under the photometric methods used in official NIOSH testing. The design analysis carried a practical bonus: filters made of finer fibers not only required less material to hit the efficiency target, they also tolerated larger manufacturing deviations in basis weight before falling out of specification, a meaningful advantage for real production lines where fiber deposition varies across a web and over time.

Comparing measured pressure drops against classical theory exposed an intriguing gap in the literature. For larger fibers, the slip-flow-modified Kuwabara model, Pich’s adaptation for small Knudsen numbers, predicted air resistance accurately. But for the finest fibers, with average diameters near 60 nanometers and Knudsen numbers around 2.2, well beyond the conventional slip regime, the model increasingly overpredicted resistance, meaning the real filters breathed even more easily than theory suggested. The deviation followed an empirical power law in the Knudsen number, with a fitted exponent of about minus 1.27. The authors stress this relationship is an observation, not a theory, and note that no validated model yet exists for either pressure drop or filtration efficiency in this transition regime, despite the considerable practical value of sub-100-nanometer fibers.

To test the concept end to end, the team fabricated prototype duckbill-style respirators by electrospinning a PCL filtration layer, with average fiber diameter of 103 nanometers, directly onto a polylactic acid spunbond substrate, then laminating a second spunbond layer to form a spunbond-nanofiber-spunbond sandwich. Panels were laser-cut and ultrasonically welded along the edges. When tested on a TSI 8130 automated filter tester under NIOSH-specified conditions, all three prototypes exceeded 95 percent filtration efficiency and stayed below the inhalation pressure-drop limit, with two of the three also clearing the stricter exhalation limit. Because mechanical filters generally gain efficiency as particles load onto them, unlike electret filters that can lose their charge and fail under loading, the pristine prototypes likely represent a floor rather than a ceiling for performance, though rising pressure drop during loading means service-life studies remain an important next step.

The biodegradability promise was put to a quantitative test as well. Incubating the nanofiber mats in a lipase solution, the researchers found that degradation rate scaled inversely with fiber diameter, exactly what is expected when hydrolysis is confined to the fiber surface, and the smallest fibers converted completely to soluble products within roughly eight hours while bulk PCL pellets lost only 13 percent of their mass over twelve days under the same conditions. The authors estimate their accelerated enzyme test runs roughly five to ten times faster than degradation in compost or soil, and they caution that real-world breakdown involves complex microbial communities and variable conditions. The results nonetheless reinforce a single design principle with triple payoffs: fibers below 100 nanometers deliver higher filtration quality factors, need less material, forgive more manufacturing variability, and vanish faster after disposal. The remaining bottleneck, they note, is the spunbond support layers, whose fibers are an order of magnitude larger and dominate the mass of the finished respirator, and a systematic shelf-life study for the moisture-sensitive nanofiber media is still needed before biodegradable N95-class respirators can leave the laboratory for the factory floor.

The choice of polycaprolactone reflects decades of industrial familiarity. The polymer, first synthesized in the 1930s, is produced by ring-opening polymerization of ε-caprolactone and is processed commercially into packaging films, adhesives, and medical devices, meaning a respirator supply chain would not depend on novel synthesis routes. Its low melting point of roughly 60 degrees Celsius, however, could constrain sterilization methods and storage conditions, a consideration the authors’ planned shelf-life work will need to address.

The electrospinning setup itself remains close to industrial practice. The researchers used a multi-needle lab-scale spinner feeding solution at half a milliliter per hour onto a rotating drum collector under modest voltage, conditions compatible with the roll-to-roll nanofiber production lines already used for commercial filtration products. Depositing fibers directly onto a spunbond substrate, rather than onto a foil that requires a separate transfer step, further simplifies scaling.

Regulatory context matters as well. NIOSH certification of a biodegradable respirator would require testing beyond the filtration bench work reported here, including exhalation valve leakage where applicable and breathing-machine evaluations of complete facepieces. The prototype duckbill respirators, assembled by ultrasonic welding without adhesives, represent an early but concrete step toward that certification pathway.

Subject of Research: Biodegradable electrospun polycaprolactone nanofiber filter media designed to meet N95 respirator filtration and breathing-resistance standards

Article Title: Electrospun biodegradable polycaprolactone filter media for filtering facepiece respirators

Article References: Ewell, N., Fleishman, S., Mulherin, K., & Rutledge, G. C. (2026). Electrospun biodegradable polycaprolactone filter media for filtering facepiece respirators. Journal of Materials Science: Polymers, 1(1), Article 21. https://doi.org/10.1007/s44493-026-00021-6

Image Credits: AI Generated

DOI: 10.1007/s44493-026-00021-6

Keywords: electrospinning, polycaprolactone, nanofibers, N95 respirators, air filtration, biodegradable polymers, aerosol filtration, quality factor, pressure drop, enzymatic degradation, personal protective equipment, green solvents