The Chinese city of Wuhan has become infamous as the course of the Covid-19 outbreak, but researchers at the university have developed a hydrogel that has dramatic potential for power systems.
The team from the MOE Key Laboratory of Hydraulic Machinery Transients at the School of Power and Mechanical Engineering at Wuhan University, along with colleagues from the Department of Bioengineering at the University of California in Los Angelese (UCLA) developed a smart thermogalvanic hydrogel film that can both cool a system and generate power from the heat at the same time.
This is a key problem as materials are optimised for one apprach or the other, either cooling or used for energy harvesting.
The film is built from an acrylamide polymer under UV illumination, which was later on dried at 65 oC and soaked in the mixed solution of K4Fe(CN)6/K3Fe(CN)6 and LiBr until fully swelled. In the film, ions and water undergo two separate thermodynamic cycles: thermogalvanic reaction and water-to-vapour phase transition. When the hydrogel is attached to a heat source, it can achieve efficient evaporative cooling while simultaneously converting a portion of the waste heat into electricity.
The hydrogel can also absorb water from the surrounding air to regenerate its water content later on.
To demonstrate the technology, a hydrogel film with a thickness of 2 mm was attached to a cell phone battery while operating. It successfully decreased the temperature of the battery by 20 °C and retrieved electricity of 5 μW at the discharging rate of 2.2 C.
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