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The sensor, designed to be worn directly on the skin, is suitable for real-time monitoring of the recovery level of not only general wounds, but also difficult-to-heal wounds, such as those with chronic inflammation. Notably, healthy skin has a pH range of 4–6. When a wound occurs, the pH is known to be approximately 7.4. In this study, alpha-naphtholphthalein (Naph) was immersed in a cotton-blended textile to produce a wearable halochromic sensor that clearly changed color depending on the pH of the skin in the range 6–9, including pH 7.4, which is the skin infection state. The coating was performed without using an organic solvent by dissolving it in micelle form using cetyltrimethylammonium bromide, a surfactant, in water. Naph-based halochromic sensor shows light yellow, which is the dye's own color, at pH 6, which is a healthy skin condition, and gradually showed a clear color change to light green-green-blue as pH increased. Even after washing and drying by rubbing with regular tap water, the color change due to pH was maintained more than 10 times. Naph-based halochromic sensors use a simple solution production and coating method and are not only reusable sensors that can be washed with water but also use environmentally friendly water, making them very suitable for developing commercial products for wound pH monitoring. In addition, it can be easily applied to medical supplies, such as medical gauze, patient clothes, and compression bandages, as well as everyday wear, such as clothing, gloves, and socks. Therefore, it is expected to be widely used as a wound pH sensor, allowing real-time monitoring of the skin condition of individuals with chronic skin inflammation, including patients requiring wound recovery. [ABSTRACT FROM AUTHOR]

We report on developing a wearable infrared (IR) display based on stretchable conductive fibers fabricated through an expansion–contraction process. The expansion process creates a gap between the strands of spandex fibers. This is achieved by immersing the fibers in a solvent where carbon nanotubes (CNTs) are dispersed, thereby embedding the CNTs. Contraction is achieved through a drying process, which removes the gap between the strands of the spandex fibers. This ensures that the CNTs remain embedded, even after repeated stretching. The CNT-embedded spandex fibers are arranged into a 5 × 7 pixel array. The intensity of the IR rays emitted from the fibers can be controlled by adjusting their temperature, which is achieved by varying the driving voltage. Full-color IR images and displays of letters and numbers are realized through precise control of the IR light intensity. The wearable IR display developed in this study opens up exciting possibilities for integration into advanced systems such as military identification, artificial intelligence robots, autonomous driving, and aerospace industry applications. [ABSTRACT FROM AUTHOR]

Studies have attempted to improve thermal conductivity by complexing polymers. Via the complexing of photothermal materials with a heat-sensitive polymer, heat can be generated internally, thus resulting in efficient changes in the properties of the heat-sensitive polymer. This study fabricated an optical writing display to locally induce heat generation in poly(N-isopropylacrylamide) (pNIPAM), which is a heat-responsive material, using the photothermal effect of a near-infrared (NIR) absorbing material. Cesium tungsten oxide (CTO), an NIR-absorbing material, exhibits excellent properties due to its photothermal properties. By mixing carbon nanotubes (CNTs), the photothermal effect caused by NIR rays was strengthened and was more effectively controlled by providing thermal conductivity characteristics. The CNT–CTO hybrid absorbed the NIR laser, converted it into heat, and transmitted it to the adjacent pNIPAM network. When pNIPAM received heat, a hydrophilic–hydrophobic phase transition occurred, and a white pattern was observed owing to a change in the refractive index inside the hydrogel. Upon stopping the application of the NIR laser, rapid cooling occurred due to the high thermal conductivity of the CNTs, and the hydrophobic–hydrophilic phase transition was quickly achieved and restored. Therefore, based on the results of this study, optical writing displays using heat-responsive polymers containing photothermal particles and NIR lasers are expected to be applicable for information transmission in extreme environments, such as aviation, space, and the military, owing to the ability of lasers to travel in a straight line. [ABSTRACT FROM AUTHOR]