Jiwon Park

Despite the rapid development of various wearable generators to harvest energy from human activity, they are limited to single or intermittent power generation. Here, stretchable and washable energy harvesting fabric is reported, which enables biomechanical and biochemical generation through co‐weaving triboelectric generator (TEG) and perspiration electric generator (PEG)‐based fibers. The two energy harvesting approaches can work individually or simultaneously, thereby combating humidity and increasing the electrical output. The maximum output power density of TEG‐ and PEG‐based fibers can achieve 166 and 5.4 µW cm⁻², respectively. The woven‐structured patch‐type energy harvester is conformable with clothing. It can harvest energy from human movements and sweat to drive the wearable Internet of Things (IoT) without charging systems. This synergistic and complementary energy harvester can provide a viable standalone power source relying solely on human activity for wearable electronics.

Piezoelectric materials are a class of materials that can generate an electric charge when subjected to mechanical stress, or vice versa. These materials have a wide range of applications, from sensors and actuators to energy-harvesting devices and medical implants. Recently, there has been growing interest in using 3D printing to fabricate piezoelectric materials with complex geometries and tailored properties. Three-dimensional printing allows for the precise control of the material’s composition, microstructure, and shape, which can significantly enhance piezoelectric materials’ performance. Three-dimensional printing has emerged as a promising technique for fabricating piezoelectric materials with tailored properties and complex geometries. The development of high-performance piezoelectric materials using 3D printing could have significant implications for various applications, including sensors, energy harvesting, and medical devices. In this review paper, 3D printing methods for piezoelectric materials, their advantages and disadvantages, representative piezoelectric ceramics, and examples of 3D printing are presented. Furthermore, the applications utilizing these materials are summarized.

The market for wearable sensors is growing rapidly as interest in personal health has recently increased, and the Internet of Things (IoT) has developed. However, supplying power to wearable sensors, such as body-attached flexible devices and E-skin, is still a matter of concern. Herein, we report a triboelectric nanogenerator (TENG)-based E-skin that can harvest bio-friendly energy and self-powered pressure sensing with its own power source. Au-coated Cu yarn and polytetrafluoroethylene-molded micro-patterned polydimethylsiloxane were used to fabricate E-skin with excellent stability, high sensitivity, elasticity, and flexibility. The TENG-based E-skin generates an output peak voltage and current of up to 200 V and 2.7 µA, respectively, and is stable with 4,500 cycles of pushing motion without any deterioration of the output signal. In addition, it is possible to operate an electronic watch by charging a capacitor and measuring the arterial pulse of the wrist as a pressure sensor. The results of this study present potential solutions for power source and signal monitoring within soft/wearable devices and human-machine interfaces.

The demand for wearable sensor technologies has increased with the recent increase interactions humans–electronic device interactions. However, the supplying power for wearable sensors, such as E-skin and flexible electronics, remains a major technical challenge. Herein, we report a triboelectric nanogenerator (TENG)-based E-skin capable of biomechanical energy harvesting and self-pressure sensing without an external power source. PTFE-molded micro-patterned PDMS and a conductive yarn were combined to implement an E-skin with flexibility, elasticity, high sensitivity, and excellent stability. The manufactured E-skin generates a power of 154 mW m ⁻² for an external force of 1 kgf and exhibits stable characteristics without deterioration of output even under 4500 cycles of repeated pressure. The E-skin can charge a capacitor and drive an electronic watch as well as monitor physiological signals, such as arterial pulses. The method used in this study can be extended to potential applications for power supply in wearable/soft electronics, medical monitoring, and human–machine interfaces.

Recently, there has been a rapidly growing interest in the application of electronic skins and wearable sensors that can be attached to the human skin or the curved parts of the human body, owing to their flexibility and elasticity. However, developing a power supply to drive such devices is a significant challenge. An on-body-based soft triboelectric nanogenerator (TENG), which can be attached to the skin and generate energy from any type of motion, is proposed to address this challenge. The manufacturing process of the proposed device is simpler than that of a similar previously developed TENG. The proposed on-body-based soft TENG is ultra-thin and has a thickness of approximately 200 μ m. Au-coated yarn, which acted as an electrode, was formed on the elastomeric substrate in a serpentine form, exhibiting high elasticity (>100%) and stable properties without distortion, even after experiencing repeated deformation. Attached to the back of the hand, TENG generated 150 mW m ⁻² power and demonstrated practical application potential because it could charge the storage element while operating the electronic device. Additionally, it was attached to different parts of the body to harvest energy with strong adhesion, even under various motions. The on-body-based soft TENG can be used as a thin and flexible soft power source for replacing existing bulk batteries and can also serve as an essential core device in various fields related to electronic skin and flexible electronic devices.

Textile or woven-structured triboelectric nanogenerators (TENGs) convert the mechanical energy generated from human motion into electrical energy and they can be used as efficient power sources for wearable and portable devices. However, the existing weaving-based woven-structured TENGs require multiple strands of fibers and have limited stretchability. In this paper, we propose highly stretchable and flexible single-strand fiber-based woven-structured TENGs (FW-TENGs). The proposed FW-TENGs can generate ∼34.4 µW/cm² power from the continuous contact and separation from skin and demonstrate durability and potential for application in electronic devices. We successfully integrated the proposed FW-TENG into a shoe and harvested the mechanical energy generated from human motion. The FW-TENG is expected to find use in various applications such as e-textiles and smart clothing because it can be manufactured on a large scale.

In the proposed fiber-based single-electrode triboelectric nanogenerator (FSTENG), energy was generated from the contact between human skin and silicone rubber.