Chapter 3. Results and Discussion
3.5 Applications of IR- and water-gating textiles
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for the recovery test of compressed SMP textile using (d) hot (~70 °C) and (e) cold (room temperature) water droplet. Inset images are OM images of SMP textile before and after the recovery test. Scale bars are 500 µm.
Even without direct contact with the heat source, hot environments can harm the human body through heat transfer.11 Our smart textile can protect the human skin from unintentional exposure to hot air or water by transforming its shape from the deformed to the original state in response to heat. Materials with adaptive IR emissivity can conceal objects, such as people, vehicles, and buildings, from IR detectors because it allows for the regulation of IR radiation without altering the actual temperature of objects.54 Figure 16a and 16b displays the photographs and infrared images for the remote recovery of the deformed SMP textile on a 50 °C hot plate by blowing hot air, which was stretched 50%. The IR images demonstrate that, after hot air for approximately 50 seconds, the distorted SMP textile’s limited thermal insulation was successfully recovered. Even under the mechanical stress caused by a weight (5.4 g), which was 174 times heavier than the SMP textile, shown in Figure 16c, the hot-air-induced shape-recovery of SMP textiles was still viable.
Figure 3.17 IR images for the remote recovery test of the SMP textile using (a) hot (~70 °C) and (b) cold water droplets.
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The distorted SMP textiles was similarly restored to its original shape by a hot water droplet, which swiftly passed through the textile in 6 seconds from the bare polymer side to the AgNW side (Figure 16d). Likewise, Figure 17a shows the IR images for the remote recovery test of the SMP textile when use hot water droplets. Shape-recovery occurred as a result of the direct heat transfer from the hot water (approximately 70 °C) to the deformed SMP textile, but the shape-recovery did not occur with cold water (Figure 16e). Also, it can be confirmed by Figure 17b. The SMP textile is applied to the human kin with the bare polymer side down (the upper side in Figure 16d and 16e, allowing water droplets to only penetrate through the textile from the skin’s surface to the outside. Therefore, the SMP textile can protect the human skin from direct contact with hot water by favor its unidirectional water penetration.
Figure 3.18 Applications of IR- and water-gating textiles on human skin. (a) Photographs of human skin without (top) and with the SMP textile (bottom) under the IR irradiation. (b) Time-dependent temperature changes of human skin measured by a contact thermometer. The intensity of IR light was 8 mW cm-2 with a distance of 50 cm between the IR lamp and skin. (c) Photographs of water removal from human skin using the SMP textile (top) and cotton (bottom). Water was dyed with blue pigment.
(d) Time-dependent change of human skin temperature after covering the water droplet with the SMP textile and cotton. The temperature was measured by the contact thermometer.
SMP textiles can effectively help maintain body temperature by obstructing external heat or preventing excessive heat loss from the human skin, which brought on by sweat evaporation. These profits come from their high thermal insulation and directional water transporting capabilities. We applied the SMP textile, which have IR- and water-gating properties, on the actual human skin and measured time-dependent temperature changes and the intensity of IR irradiation. First, the human skin was protected from IR irradiation by being covered in the SMP textile (Figure 18a). The temperature of
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the skin covered in SMP textile (36.1 °C) after being exposed to IR irradiation for 70 seconds, showing effective IR irradiation blockage (Figure 18b). Second, by eliminating sweat from the skin and reducing heat loss, the SMP textile helps to keep the body temperature stable. When the human skin was covered with the SMP textile, as shown in Figure 18c (top), water was removed from the skin and directionally transported to the outer layer. On the other hand, the skin’s commercial cotton fabric partially removed the water, leaving residue (Figure 18c, bottom). Consequently, when the SMP textile was worn, the human skin successfully regained its temperature following the quick elimination of water (Figure 18d).
It also indicated by IR images of the human skin after water removal using the SMP textile and cotton (Figure 19). On the other hand, the remaining water under the cotton continued to cool the skin, and after 10 minutes, the temperature of the cotton-covered region was 7.2 °C lower than that of the SMP textile-covered region. Additionally, directional water transportation was even achievable from the bottom, bare polymer side, to the top, AgNW side, of the SMP textile, demonstrating that the driving force of the water transportation was stronger than the driving force of gravity, shown in Figure 20.
Figure 3.19 IR images of human skin after water removal using the SMP textile and cotton. (a) Photograph and (b) IR image of the human skin after attaching the SMP textile and cotton to a water droplet on the human skin. IR images at (c) 60 s and (d) 90 s after detachment of the SMP textile and cotton from the human skin.
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Figure 3.20 Side-view images of the water transportation test of (a) the SMP textile (bottom: the bare side; top: the AgNW side) and (b) the cotton fabric. The water droplets were placed under the fabrics and were dyed blue to improve the visibility.
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