Development of a Flexible Thin Wearable Device for Tuning Temperature, Humidity, and Surface Friction on Its Surface

Abstract

This study proposes a wearable device that adapts its surface conditions to maximize user comfort using novel strategies to change its temperature, humidity, and friction. The device consists of three functional units, namely heating, liquid injection, and dry-air blowing units, composed of flexible materials and thin structures. Owing to its flexibility and thickness, it can be installed on garments. The surface conditions change according to the collaborative actions of the three functional units. The temperature is increased using the heating unit and decreased using both the liquid-injection and dry-air blowing units. Humidity is increased and decreased by the liquid-injection and dry-air blowing units, respectively. Finally, the friction of the contact surface area of the device with human skin is increased and decreased using the liquid-injection and dry-air blowing units, respectively. These methodologies are experimentally validated under different environmental conditions. The validation reveals that the injection of a liquid (deionized water) increases surface friction, whereas blowing air decreases friction; in particular, the presence of granular objects is effective at reducing friction. In addition, the environmental conditions of temperature and humidity influence the degree of increase or decrease, primarily because the amount of water is varied to change the humidity, lower the temperature, and increase friction: vaporization heating lowered temperature and adhesion force of water increased friction. The temperature, humidity, and kinetic friction of the wearable device range from −2.6 to +5.0 °C, −19% to +12%, and −73% to +45%, respectively.