Taekyung Lim

As climate change intensifies, summer temperatures are gradually rising, resulting in an increase in heat-related illnesses among individuals exposed to heatwaves. Consequently, wearable sensors for external environmental monitoring are gaining prominence as personal healthcare and safety diagnosis systems. Wearable temperature sensors must provide stable sensing even when subjected to various external environmental changes, such as repetitive movement, humidity, and water contact. In this study, a fiber-type temperature sensor with an embedded MXene (Ti3C2Tx) was fabricated. MXene was synthesized by etching aluminum (Al) from Ti3AlC2 (MAX phase powder) using a mixture of Li salt and hydrochloric acid (HCl) and then prepared as an aqueous dispersion. Subsequently, conductive fibers were fabricated by embedding MXene into polyester fibers via a dipping–drying process. To mitigate susceptibility to moisture, hydrophobic 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecylphosphonic acid (HDF-PA) was applied to the surface of the MXene embedded in the fiber, providing hydrophobicity. The temperature range of 0–50 °C was monitored by measuring the resistance change in the fabricated HDF-PA-coated MXene-embedded fiber. Furthermore, sensing characteristics remained robust even under a bending radius of 15–3 mm. In addition, the sensor was confirmed to operate stably despite physical deformation from repeated bending up to 1000 times, as well as exposure to 50%–90% RH and 1 h of immersion in water, demonstrating excellent durability and water resistance.

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.

Polydimethylsiloxane (PDMS) is a highly reliable thermosetting polymer with exceptional chemical and mechanical resistance, as well as remarkable water repellency and adhesive performance. Its unique features make it the preferred choice for fluorine-free hydrophobic coatings. However, the use of PDMS requires organic solvents that are toxic and environmentally hazardous. In this study, an emulsion composed of amine-terminated polydimethylsiloxane (PDMS-NH2) in an environmentally friendly solvent, water, was prepared. Subsequently, glutaraldehyde (GA) was added and crosslinked to generate a hydrophobic PDMS–GA emulsion. The PDMS–GA emulsion is a low-viscosity solution that can infiltrate different types of fabrics (cotton, nylon, and polyester) or paper with numerous intertwined fibers. After dipping the fabrics and paper into the prepared PDMS–GA emulsion, they were washed in an aqueous solution containing dispersed kaolin particles and dried to yield a rough structure. As a result, a hydrophobic surface with a water contact angle of 151.2° was achieved. Furthermore, after exposure to strongly acidic or alkaline solutions (pH 1–13) and washing six times with water, the hydrophobic fabric remained chemically stable. Additionally, it withstood ten tape peeling tests, proving its mechanical durability. Crucially, the hydrophobic treatment method does not involve fluorine and uses eco-friendly water as the solvent. Therefore, this is a convenient way to apply waterproof coatings to functional textiles that require water resistance and are expected to have great industrial applications.