Researchers at Linköping University in Sweden have created what they say is a heat-gated organic transistor.
Heat-driven transistor. Image credit: Linköping University.
“We demonstrated for the first time that heat signal can act as input for logic circuits, opening up new possibility to couple electrical conductivity with thermoelectricity, in the new field of thermoelectronics,” said Linköping University Professor Xavier Crispin and co-authors.
The team’s heat-gated transistor consists of an electrolyte-gated transistor and an ionic thermoelectric supercapacitor.
In the capacitor, heat is converted to electricity, which can then be stored in the capacitor until it is needed.
Prof. Crispin and his colleagues searched among conducting polymers and produced a liquid electrolyte with a 100 times greater ability to convert a temperature gradient to electric voltage than the electrolytes previously used.
The liquid electrolyte consists of ions and conducting polymer molecules. The positively charged ions are small and move rapidly, while the negatively charged polymer molecules are large and heavy. When one side is heated, the ions move rapidly towards the cold side and a voltage difference arises.
According to the team, the heat-gated transistor opens the possibility of many new applications such as detecting small temperature differences, and using functional medical dressings in which the healing process can be monitored.
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 — a hundred times greater than traditional thermoelectric materials — 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.’ 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.
The research was published Jan. 31, 2017 in the journal Nature Communications.
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D. Zhao et al. 2017. Ionic thermoelectric gating organic transistors. Nat. Commun. 8, 14214; doi: 10.1038/ncomms14214
