هەموو جۆرەکان


To detect the human body sweating is automatically open cooling of smart clothing

کات:2022-01-17 لێدانەکان:

The contribution of thermal and humidity comfort to the overall comfortable feeling of clothing accounted for 61.5%, and the heat transfer between clothing and the environment mainly included conduction, convection, radiation and sweat evaporation. Li ser vê bingehê, a variety of intelligent textile clothing can realize personal thermal and humidity comfort management is developed.

A team at Duke University has demonstrated a multimodal adaptive wearable device with a polyamide/metal heterostructure wet-responsive flap that simultaneously regulates convection, sweat evaporation, and mid-infrared emission in response to human sweat stimulation to achieve rapid heat transfer regulation.
In order to achieve multimodal thermal management, three layers of nylon, Ag and SEBS nanocomposites and a set of flaps were designed. Nylon 6 can be driven by reversible water absorption and water discharge, that is, when there is a humidity difference on both sides, the nylon flap will bend to the direction of lower humidity, and return to the original state after the humidity difference disappears. A layer of Ag is deposited on the top surface to achieve low mid infrared emission. When the flap is closed in the dry state, this layer can effectively suppress the radiation loss; When flaps are opened in humid conditions, radiation heat transfer is increased due to the near-perfect blackbody of human skin.

The experimental results show that the bending Angle of the polyamide Ag50 (Ag sample deposited on the polyamide with a thickness of 50 nm) can reach 260° when water is introduced. When the relative humidity changes from 40% to 80%, the polyamide Ag50 can fully open within 14 s and return to the initial state when the relative humidity gradient disappears at 45 s. If the humidity is kept at 80%, the bending Angle can remain unchanged for 2h. In addition, polyamide -Ag50 also showed excellent stability, bending Angle unchanged after 200 cycles.

The metal layer can not only improve the bending property of nylon, but also inhibit the infrared emission of human body. Even if the Ag layer is only 20 nm thick, its infrared emissivity can be reduced to only 0.1. Since the transparency of nylon in mid-infrared band is about 44%, the Ag layer at the top can also increase the mid-infrared reflectivity from below, directly reflecting and capturing the thermal radiation of the human body, so as to achieve better heat dissipation effect.
Compared to conventional static textiles and single-mode adaptive wearables, the multi-mode adaptive devices were about 16% warmer when the flaps were closed (dry conditions) and 14% cooler when the flaps were open (wet conditions) without any power or energy input, expanding the thermal comfort zone by 30%. The device was attached to the back of a commercially available T-shirt and volunteers were tested outdoors. The flaps were initially closed and fully opened when the subjects began exercise (about 5 minutes). As expected, the flaps of the device returned to the initial closed state when the subjects stopped exercising and the sweat disappeared completely.

Related work was carried out by "Metalized polyamide heterostructure as a moisture-responsive actuator for multimodal adaptive personal heat Management "was published in Science Advances.

The thesis links: https://www.science.org/doi/10.1126/sciadv.abj7906