Yujang Cho

The growing demand for sustainable energy solutions has increased interest in ambient energy harvesters capable of continuous operation under diverse environmental conditions. Here, we report a hygroscopic moisture‐electric generator (HMEG) that achieves long‐term, self‐sustained power generation through an asymmetric architecture composed of montmorillonite and calcium chloride. The integration of hygroscopic materials within a perforated coin‐cell structure enables directional moisture transport and persistent ionic gradients, producing a stable open‐circuit voltage of 0.55 V and a short‐circuit current of 74 µA for 30 days at 50% relative humidity. The device delivers a maximum power density of 3.582 µW cm ^{− 2} and exhibits strong scalability, with a large‐area HMEG (7 × 7 cm ² ) producing 0.64 V and 816 µA for three days. A ten‐unit array further outputs 5.5 V and 670 µA, confirming modular energy‐harvesting capability. Beyond power generation, a single HMEG enabled in vitro electrical stimulation of L929 fibroblast cells, enhancing wound‐healing‐related behaviors. The stimulated group showed a 152% increase in cell‐covered area on day 3 and 241% on day 5, along with elevated metabolic activity (32.1% and 23.4%). These results establish a durable and biocompatible platform linking moisture‐driven energy harvesting with regenerative bioelectronics.

Porous organic polymers (POPs) offer exceptional surface area, tunable pore sizes, and versatile chemical functionality, making them attractive for a range of advanced applications. However, their conventional powdered form limits processability, structural integration, and practical deployment. Integrating POPs into fibrous matrices through electrospinning, a scalable and versatile technique for producing nonwoven fibers, helps overcome these limitations and enables the creation of new material architecture. The resulting POP‐incorporated fibrous materials (POP‐FMs) combine the intrinsic advantages of POPs with enhanced mechanical integrity, tailored surface properties, and improved mass transport characteristics. These features expand the potential of POP‐FMs in areas such as catalysis, environmental remediation, sensing, and biomedical fields. This review discusses recent progress in the design and synthesis of electrospinning‐compatible POPs, strategies for fabricating POP‐FM composites, and the structure–property relationships that govern their performance. Key challenges and future directions are also explored, underscoring the potential of POP‐FMs as next‐generation functional materials.

Electrospinning has emerged as a transformative technique for fabricating nanofibers (NFs), offering precise control over their morphology, composition, and functionality. This versatile process facilitates the production of fibers ranging from nanoscale to microscale with customized properties, integrating diverse materials and architectures for advanced research and industrial applications. This review presents recent advancements in electrospinning, addressing its fundamental principles, nanomaterial synthesis methods, and examples from a wide range of applications. The significant progress that are made in fabricating polymer, metal oxide, carbon, and composite NFs with diverse architectures such as porous, core–shell, hollow, and aligned structures is highlighted. Advanced electrospinning techniques, including coaxial electrospinning, aligned electrospinning, yarn electrospinning, and roll‐to‐roll processes, demonstrate the scalability and adaptability of electrospinning for the development of next‐generation nanomaterials. Electrospun NFs are being actively applied to functional membranes, gas sensors, energy systems, and catalytic processes, addressing critical challenges in these respective areas. In conclusion, the groundbreaking potential of integrating artificial intelligence (AI)‐driven optimization with sustainable material design, such as the use of environmentally‐friendly “green” solvents, is emphasized. In the end, leveraging robotics‐based electrospinning and AI‐enhanced methodologies is essential to achieve stable scalability, optimized performance, and sustainability for research and industry.

The global energy crisis caused by the overconsumption of nonrenewable fuels has prompted researchers to develop alternative strategies for producing electrical energy. In this review, a fascinating strategy that simply utilizes water, an abundant natural substance throughout the globe and even in air as moisture, as a power source is introduced. The concept of the hydrovoltaic electricity generator (HEG) proposed herein involves generating an electrical potential gradient by exposing the two ends of the HEG device to dissimilar physicochemical environments, which leads to the production of an electrical current through the active material. HEGs, with a large variety of viable active materials, have much potential for expansion toward diverse applications including permanent and/or emergency power sources. In this review, representative HEGs that generate electricity by the mechanisms of diffusion, streaming, and capacitance as case studies for building a fundamental understanding of the electricity generation process are discussed. In particular, by comparing the use and absence of hygroscopic materials, HEG mechanism studies to establish active material design principles are meticulously elucidated. The review with future perspectives on electrode design using conducting nanomaterials, considerations for high performance device construction, and potential impacts of the HEG technology in improving the livelihoods are reviewed.

As a method to maximize the energy efficiency of triboelectric nanogenerators (TENGs), high‐voltage charge injection (HVCI) on the surface is a simple and effective method for increasing surface charge densities. In this study, positive and negative triboelectric series are controlled using a 3‐layer gradient charge‐confinement wherein the particle sizes of the mesoporous carbon spheres (mCSs) are sequentially arranged depending on the external surface area of the mCSs. In the gradient charge‐confinement layers of this study, the mCS with different sizes perform charge transport from the surface to a deep position during HVCI while mitigating the charge loss through charge confinement to induce the high space charge densities. Through this process, the output voltage—which is initially 15.2 V—is measured to be 600 V after HVCI, thus representing an increase of about 40 times. Further, to amplify the low output current, which is a disadvantage of triboelectric energy, two types of electrical energy—triboelectric and electromagnetic energy—are produced in single mechanical motion. As a result, the output current produced by the cylindrical TENG and electromagnetic generator is recorded as being 1300 times higher, increasing from 12.8 µA to 17.5 mA.

The coexistence of increasingly severe environmental concerns and bio‐signal sensing systems drives the development of environmental affinity and energy harvesting materials. Chitosan is a richly sourced biodegradable material derived from crustaceans, which provides a new option for environmentally, wearable triboelectric nanogenerator (TENG). In this paper, the triboelectric performance of chitosan blends are proposed to enhance the dielectric constant by optimizing the ionic polarization and interface polarization for the first time, which fills in the blank of enhancing the output of chitosan triboelectric by systematically engineering in ionic/molecular and pH effect. Triboelectric output enhanced chitosan film in TENG shows an output voltage 3 times (18 V) higher than that of the initial film and 25 times (200 V) higher after corona charge injection. The chitosan film for wearable devices not only can be used as a unit of a triboelectric device to measure human motion signal, but also can be used as a piezoresistive sensor (ΔR/R₀: 0 to 1.5) and an air humidity sensor (relative humidity: 20% to 90%) after mixing carbon black. The study provides a stimulating example that triboelectric nano generator/piezoresistive sensor is made from chitosan and used in the multi‐modal sensing system.

Recently, wearable sensors, due to their ability to exhibit characteristics, have been appealing for health monitoring through detection of human motions and vital signals. The development of strain sensors with high sensing performance and wearability has been a great challenge to date. In this study, a textile-based strain sensor with good skin affinity was fabricated through a simple fabrication process of dip-coating 2D triaxial-braided fabrics using carbon ink and then drying. The macro crack aligned on the 2D triaxial-braided fabric with a high-density structure and good recovery force. The sensitivity of textile-based strain sensor can be enhanced due to aligned macro crack formed by prestrained fabricating process and characteristic of the 2D triaxial braided fabric with high dense structure. The optimized sensor exhibits high sensitivity (gauge factor: 128) in a strain range of 0–30%, durability (5000 cycles), washability, low hysteresis, and fast response time (90 ms). Therefore, it can be applied as a wearable sensor that can monitor human motions (large strain) and biosignals (subtle strain).

In this study, we fabricated a wearable strain sensor to monitor human respiration by lock-stitching stretchable conductive yarn onto a textile substrate. We developed the strain sensor by using conductive yarn consisting of silver-plated and unplated nylon yarns twisted around a lycra fiber with a lock wrinkle structure that could stretch after sewing. The slopes of the strain-stress curves of three fabricated strain sensors with a 10% strain load increased to 121 kPa, 189 kPa, and 241.5 kPa, and the relative change in resistance (ΔR/R0) of the strain sensor increased from 67% to 116% and from 8% to 109% by respectively applying more tension and fewer locks to the conductive yarn. In addition, as we strained the strain sensor to more than 4,000 cycles, the relative change in resistance decreased by only 6% from its initial value. A respiration measurement test was conducted with the developed sensor to monitor four different respiration patterns: slow (10 bpm), fast (30 bpm), deep, and shallow respiration, and the results were compared to those of reference respiration monitoring devices. Consequently, the proposed stretchable conductive yarn-based strain sensor worked as well as commercial respiration sensors, and its feasibility was demonstrated for use in respiration monitoring for daily living.