Novel film that keeps us dry and cool

A team of researchers from NUS has created a novel film that is very effective in evaporating sweat from our skin to keep us cool and comfortable when we exercise, and the moisture harvested from human sweat can be used to power wearable electronic devices such as watches, fitness trackers, and more. The main components of the novel thin film are two hygroscopic chemicals – cobalt chloride and ethanolamine. Besides being extremely moisture-absorbent, this film can rapidly release water when exposed to sunlight, and it can be ‘regenerated’ and reused more than 100 times. To make full use of the absorbed sweat, the NUS team has also designed a wearable energy harvesting device comprising eight electrochemical cells (ECs), using the novel film as the electrolyte. Each EC can generate about 0.57 volts of electricity upon absorbing moisture. The overall energy harvested by the device is sufficient to power a light-emitting diode. This proof-of-concept demonstration illustrates the potential of battery-less wearables powered using human sweat. This technological breakthrough was reported in the September print issue of the scientific journal Nano Energy.

The NUS team packaged the film into breathable and waterproof polytetrafluoroethylene (PTFE) membranes, which are flexible and commonly used in clothing, and successfully demonstrated the application of the moisture-absorption film for underarm pads, shoe linings, and shoe insoles.