Putting air moisture to good use

28 May 2018 | Research
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Asst Prof Tan and his team from NUS Materials Science and Engineering invented the novel water-absorbing gel

A new water-absorbing gel could help prevent mouldy walls at home and make waiting at the bus stop during hot and humid weather more comfortable. This unique hydrogel can do even more after harvesting moisture from air — it functions as a sun or privacy screen, conductive ink and an emergency battery.

Developed by Assistant Professor Tan Swee Ching and his team from NUS Materials Science and Engineering, the material can absorb water from the surroundings more than 2.5 times its weight and performs at least eight times better than commercial drying agents such as silica gel. It is also cheap and easy to produce.

The hydrogel is suitable for tropical countries like Singapore, where the surrounding air feels hotter than the actual ambient temperature due to the high levels of relative humidity between 70 and 80 per cent.

“Moisture in the air is an abundant resource, but there are few attempts to harvest and put it to good use. Our hydrogel reduces relative humidity of a confined space from 80 per cent to 60 per cent within the thermal comfort zone in less than seven minutes and achieves a cooling effect,” said Asst Prof Tan.

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The hydrogel harnesses humidity for a wide range of useful applications

The novel material does not need electricity to operate and functions both indoors and outdoors. A unique form of zinc oxide that exists in a gel-like state, the compound is more commonly found in white powder form and used in sunscreens.

It displays interesting optical, electrical and electrochemical properties after absorbing water and can be used for various practical applications.

Moisture in the air is an abundant resource, but there are few attempts to harvest and put it to good use. Our hydrogel reduces relative humidity of a confined space from 80 per cent to 60 per cent — within the thermal comfort zone — in less than seven minutes and achieves a cooling effect.

The hydrogel can be used as a smart window material to block heat from sunlight, lowering ambient temperatures in an enclosed space by more than seven degrees Celsius. As the hydrogel turns from transparent to opaque after taking in water, it can also double up as a privacy screen.

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The hydrogel can generate about 1.8 volts of electricity which is sufficient to power a small digital clock

It is also suitable as a conductive ink on printed circuit boards commonly found in electronic devices. Given its gel-like consistency, it is highly attractive for flexible electronics. It can be easily washed away using common solvents such as vinegar, thus enabling the reuse of circuit boards and helping to cut down on electronic waste.

The hydrogel can also serve as an emergency power source. Asst Prof Tan explained, “If a person is stranded in the jungle where sunlight gets blocked and there is no electricity, he or she can potentially let the hydrogel absorb some water from surrounding air to generate power to make an emergency call.”

The NUS Engineering team has filed a patent for their invention and will conduct more studies to further advance the different applications of the hydrogel.

With support from the NUS Industry Liaison Office, the researchers have received substantial funding from Temasek Foundation Ecosperity to test the reduction of relative humidity on a larger scale in both indoor and outdoor spaces.

The research findings have been published online in the scientific journal Energy & Environmental Science on 24 May.

See press release.