Fully printed polymer capacitive gas sensor for ammonia and toluene detection

In this work an approach for the fabrication of a fully printed polymer device applicable as a capacitive gas sensor is presented. The fabrication techniques and optimal conditions for the sequential screen printing of additive polymer layers (electrodes, interface layers, and dielectric) of a printed polymer device (capacitor) was selected and optimized. The necessary adhesion of the printed functional layers to each other and to the substrate surface was ensured via the modification of the substrate surface/dielectric surface with oligomerized 3-aminopropyltriethoxysilane from solution followed by thermal annealing. The fabricated sensors demonstrated a reversible response to ammonia in a wide range of concentrations from 0 to 24 ppm, with a detection limit of 1.5 ppm in dry air. They did not lose their functionality in humid air up to a relative humidity of at least 40%, although the detection limit simultaneously increased up to 4 ppm. The printed devices can serve as disposable sensors for the presence of toluene in the atmosphere in the concentration range of 0.1–1.0 vol.%, which potentially allows them to be used for the detection of toluene leaks. The use of these printed capacitive sensors in combination with gas sensors based on organic polymer field-effect transistors makes it possible to considerably expand the range of measured ammonia concentrations: from concentrations comparable to the threshold limit value of residential areas to concentrations requiring the immediate evacuation of the population.