It is widely recognised that the thermal comfort of a human being while carrying out sporting activities has a direct impact on sporting performance, in particular when taking part in endurance sports [1]. Technology that aids personal thermal management, creating a local thermal envelope around a human body, not only improves sporting performance, but additionally, enhances the thermal comfort of individuals. Additionally, there is potential to reduce energy consumption by using personal thermal management systems, as the heating and cooling of entire building spaces would not be as necessary [2].

Thermal management systems are generally considered as ‘passive’ or ‘active’ dependent on the mechanism. Applications with a passive heating mechanism incorporate materials that have low thermal conductivities and high infrared reflectance. In this case the temperature is regulated by blocking heat transfer through the material. An example of a product that uses passive heating is the ‘space blanket’, which was developed by NASA in the 1960s to lessen the harsh temperature differences in space, via reflectance of infrared radiation. Incorporating passive heating brings advantages including typically being a low cost method, straightforward to implement, as well as energy efficient. However, these types of materials are often static and unresponsive to personal and environmental changing conditions. Active heating technologies, however, use a different mechanism. These applications drive the flow of heat via electrical and mechanical energy to regulate the temperature, such as in electrothermal, heating/ventilation/air conditioning devices. Moreover, it is generally not considered practical to use active heating technologies, particularly during performance sports. This means that a thermal management system that combines the low cost, straightforward implementation, and energy-efficient advantages of passive systems, with the on-demand, dynamic control capabilities of an active system is extremely desirable to enhance athletic performance and thermal comfort.

The skin of a squid has dynamic colour-changing properties. This is due to red, yellow and brown chromatophore organs displayed in an aligned pattern, which consist of a central pigment cell surrounded by innervated muscle cells. This advanced design in nature enables the pigment cells to be replaced by the muscle cells, switching between contracted minute points to expanded flattened disks. This switching mechanism rapidly changes the appearance of the skin’s colour and alters the transmission of light through the skin.

Research has found that the mechanism of colour-changing squid skin, exhibits almost all the capabilities needed for wearable thermal on/off switches, enabling researchers to draw inspiration for novel personal thermal management systems from this mechanism. In this innovation profile, WTiN reports on a research outcome from a collaboration led by scientists at the University of California, Irvine, US, together with the company Under Armour, Inc. [3], for the development of a new temperature regulating textile material where the amount of heat which is trapped or released can be controlled by the wearer.