Matras English – Scientists from the South-East University of Nanjing developed a new coating for thermoelectric generators converting the human body heat into electricity. This technology opens the way to creating clothes and gadgets capable of themselves, e.g., for healthcare, sports and “smart” textiles.
Thermoelectric generators (TEGs) are packaged appliances converting the human body heat into electricity without batteries or wires.
Their operation is based on the difference of temperatures: one side is warmed up by the skin, and the other side remains cold. Electric current is generated due to this differential. Such generators may be built into a bracelet, for example, into adhesive bandage or cloth to feed detecting elements, fitness equipment or small sensors.
However, sufficient temperature differential needs to be maintained for TEG efficient operation, and this where portable devices face a challenge: their external side warms up very quickly from the body and ambient air causing the differential decrease, and hence less energy is generated. Special coating casting the sunlight backward are often used for cooling, but as rule they are fastened by glue.
The glue not only makes the heat flow worse, but reduces the flexibility and durability of the appliance, with time, the glue may exfoliate when moving and bending.
To resolve this problem, the Chinese researchers created a structure combining the coating and the TEG shell without using any glue. The made both elements from one and the same material — an elastic, bio-compatible polymer polydimethylsiloxane (PDMS).
Micro particles of titanium dioxide (TiO₂) and yttrium oxide (Y₂O₃) were added to the coating Вproviding for high reflectivity and ability to emit heat into atmospheric window the wavelength band sending the radiation directly into outer space. The coating is applied by overspray method, which allows for receiving durable, homogeneous and flexible layer.
The research comprised lab tests and street tests in Nanjing. In the controlled environment without the sunlight the appliance demonstrated the 17% growth of output voltage vs the traditional one with the glue fixation and 21% growth when exposed to the sunlight.
In real street environment in a hot sunny day the appliance reached the maximum достигло voltage of 4.78 MW/cm², almost 50% higher than the sample with the glue fixation.
Also, the new coating demonstrated high mechanical strength: it turned out to be 4.4 times more resistant to break-offs, it was able to withstand the strain two times more and kept stable performance even after 250 cycles of bending and stretching.
Thus, the Chinese scientists made a step forward towards creating light and reliable autonomous energy sources, which may be integrated into clothes and portable electronics from medical sensors and fitness gadgets to “smart” textile, such as clothes with controlled heating, light indicators and materials capable of recharging portable devices or even data transfer via Bluetooth.
