Researchers from Linköping University, have created a thermoelectric organic transistor. A temperature rise of a single degree is sufficient to cause a detectable current modulation in the transistor.
“We are the first in the world to present a logic circuit, in this case a transistor, that is controlled by a heat signal instead of an electrical signal,” states Professor Xavier Crispin of the Laboratory of Organic Electronics, Linköping University.
Many Possible Applications
The heat-driven transistor is developed by Dan Zhao, principal research engineer, and Simone Fabiano, senior lecturer at the Laboratory of Organic Electronics.
It broadens a complete range of endless possibilities of many new applications such as detecting small temperature differences. In medical field it can be used to monitor healing process using functional medical dressings.
It is also possible to produce circuits controlled by the heat present in infrared light, for use in heat cameras and other applications.
The high sensitivity to heat – 100 times greater than traditional thermoelectric materials. It means that a single connector from the heat-sensitive electrolyte, which acts as sensor, to the transistor circuit is sufficient.
One sensor can be combined with one transistor to create a “smart pixel”.
This is the heat driven transistor on Laboratory of organic electronics, Linköping University. Credit: Thor Balkhed
A matrix of smart pixels can then be used, for example, instead of the sensors that are currently used to detect infrared radiation in heat cameras.
With more developments, the new technology can potentially enable a new heat camera in your mobile phone at a low cost, since the materials required are neither expensive, rare nor hazardous.
The heat-driven transistor is a sequel to the already built research that led to the production of supercapacitor a year ago, charged by the sun’s rays.
In the capacitor, the sun’s heat is trapped and converted to electricity, which can then be stored in the capacitor until used.
How it works?
The researchers at the Laboratory of Organic Electronics had looked among different conducting polymers to produce a liquid electrolyte.
This liquid electrolyte is able to convert a temperature gradient to electric voltage with a record 100 times greater ability than the previously used electrolytes.
The liquid electrolyte basically consists of ions and conducting polymer molecules. The positively charged ions are relatively small and move rapidly. In comparison to their counterpart, negatively charged polymer molecules are large and heavy.
On heating one side, the small (positively) ions move rapidly towards the cold side and a voltage difference arises.
“When we had shown that the capacitor worked, we started to look for other applications of the new electrolyte,” says Xavier Crispin.
Through their study, Dan Zhao and Simone Fabiano, have shown, after long hours in the laboratory, that it is fully possible to build electronic circuits that are controlled by a heat signal.
Reference Article: Ionic thermoelectric gating organic transistors, Dan Zhao, Simone Fabiano, Magnus Berggren and Xavier Crispin, Linköping University, Campus Norrköping, Nature Communications 2017. DOI 10.1038/ncomms14214