How to use body heat to power wearable devices
Flexible electronics technology has been known for several years now in the form of flexible electrical connections and circuit boards.
With the further development of this technology and smaller and more intelligent components being designed (IC and SOC radios, microprocessors, nanotech sensors), flexible electronic products are finding more and more application and becoming “smarter” in their everyday use.
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Uses of Flexible electronics technology
Until now the most popular uses of this technology have focused human performance monitoring.
Aircraft pilots and other personnel whose levels of attention and awareness are a critical part of their assignment as well as athletes who can record their performances and benefit hugely from the large amount of data that this technology can gather.
Also ordinary people can benefit from flexible electronics especially for health purposes as blood pressure, heartbeat patterns and rate, blood sugar, skin temperature, respiration rate, brain functions can be monitored remotely.
This technology is also finding use like in the food processing, shipping, and display market where temperature tags for perishable food are being tested or even in the military sector where Electronic Leaflets have been used in critical situations to alert population on the ground to imminent danger.
Flexible electronics technology powered up by body heat
Scientists have now pushed this technology even further and, with an innovative research, North Carolina State University engineers have designed a flexible thermoelectric energy harvester that uses body heat as the only source of energy.
Until now, one of the downsides of flexible devices was their performance as it was still inferior compared to rigid devices, which have always been superior converting body heat into usable energy.
Mehmet Ozturk, professor of electrical and computer engineering at NC State and corresponding author of a paper describing the work explained how the intention of the study was to tackle this performance issue:
“We wanted to design a flexible thermoelectric harvester that does not compromise on the material quality of rigid devices yet provides similar or better efficiency,” he and continued “Using rigid devices is not the best option when you consider a number of different factors.”
One of the challenges of this process was the connect thermoelectric elements in series using reliable, low-resistivity interconnects.
The solution for this problem was found in the use of a liquid metal of gallium and indium – a non-toxic alloy called EGaIn.
Ozturk explained how:
“the electric resistance of these connections is very low, which is critical since the generated power is inversely proportional to the resistance: Low resistance means more power.”
Another of the advantages of this technology is a certain self-healing function.
If a connection is broken, the liquid metal can reconnect to make the device work efficiently again.
This a great advantage compared to rigid devices as these are not able to heal themselves.
The researchers are very optimistic at this stage and believe that if parasitic resistance can be further reduced the efficiency of this flexible devices could increase hugely.
Future uses of flexible technology
Wearable electronic devices could soon become the future of fashion and technology. The next-generation of these devices is expected to be highly responsive completely self-powered.
However, as technology is taking us toward autonomous devices that can improve quality of life for the global population, scientist believe that the concept adopted in wearable electronic devices could be also used to improve the performances in smart buildings and smart cities.