A team of researchers created a novel physical film capable of efficiently evaporating sweat from our skin — keeping us comfy and cool while exercising, according to a recent study published in the journal Nano Energy.
Additionally, this new invention can harvest sweat moisture, and convert it into power for wearable electronics, like fitness trackers, watches, and more.
New film can evaporate sweat six times faster, holds 15 times moisture
Sweating is a normal process our bodies use to reduce thermal stress. "Sweat is mostly composed of water," said the leader of the research team Assistant Professor Tan Swee Chang, of the National University of Singapore's (NUS') department of material science and engineering. "When water is evaporated from the skin surface, it lowers the skin temperature and we feel cooler."
"In our new invention, we created a novel film that is extremely effective in evaporating sweat from our skin and then absorbing the moisture from sweat," added Tan. "We also take this one step further — by converting the moisture from sweat into energy that could be used to power small wearable devices."
Each electrochemical cell can generate 0.57 volts
The main elements of the thin novel film are two hygroscopic chemicals — called ethanolamine and cobalt chloride. Beyond its extreme capacity to absorb moisture, this invention can rapidly release water when exposed to direct sunlight. Additionally, users may "regenerate" and reuse the film more than 100 times.
The team of NUS researchers also successfully developed a wearable energy harvesting device composed of eight electrochemical cells (ECs) — to enable the efficient use of absorbed sweat. This setup uses the new film as the electrolyte, according to the study.
Every EC can generate roughly 0.57 volts of electricity once it's absorbed moisture. The total energy the device can harvest is enough to power one light-emitting diode — a proof-of-concept evoking the significant potential for battery-less wearables powered via human sweat.
Packaged film successfully proved in underarm pad, shoe insole, lining
Under conventional circumstances, hygroscopic materials like zeolites and silica gels possess low bulk solid structures and water uptake — which makes them an unsuitable option for the absorption of moisture when sweat evaporates. Comparatively, the novel moisture-absorbing film from the NUS researchers gathers 15 times more moisture, at six times the speed than typical materials.
This novel film also shows a color change when it absorbs moisture, changing from blue to purple, and eventually pink. This feature can indicate the degree of moisture absorbed at any given point.
The research team at NUS packaged the novel film into breathable, waterproof polytetrafluoroethylene (PTFE) membranes, which provide a flexible and frequently-used substrate for applications in clothing. This packaged application was successfully demonstrated to absorb moisture in underarm pads, shoe lining, and the shoe insole.
NUS research team aims to incorporate film in consumer products
"Underarm sweating is embarrassing and frustrating, and this condition contributes to the growth of bacteria and leads to unpleasant body odor. Accumulation of perspiration in the shoes could give rise to health problems such as blisters, calluses, and fungal infections," said Professor Tan. "Using the undearm pad, show lining and shoe insole embedded with the moisture-absorbing film, the moisture from sweat evaporation is rapidly taken in, preventing an accumulation of sweat and provides a dry and cool microclimate for personal comfort."
"The prototype for the shoe insole was created using 3D printing," said research team co-leader Professor Ding Jun, who is also associated with the NUS department of materials science and engineering. "The material used is a mixture of soft polymer and hard polymer, thus providing sufficient support and shock absorption."
While it's too soon to look for this novel, sweat-transforming film in electronics and athletics stores, the NUS team aims to work with private companies to incorporate the invention into future consumer products.