Printed Capacitive Sensors Based on Ionic Liquid/Metal-Organic Framework Composites for Volatile Organic Compounds Detection

In this paper, the potential of 2D printing technologies to create thin film gas sensors from ionic liquid (IL)/metal-organic framework (MOF) composites is evaluated. To accomplish this, the MOF is synthesized solvothermally, and impregnated with the IL. The structure and basic properties of the IL/MOF composites are characterized using thermal, spectroscopic, and X-ray diffraction techniques, and the resultant sensing capacity of the bulk material is evaluated by impedance spectroscopy. The IL/MOF systems are then integrated into a 2D printed silver capacitive circuit by spray and tested on a custom-made gas flow apparatus. Exposure of the IL/MOF based sensors to water, acetone, and ethanol induces a repetitive variation of the capacitance (from 0.05 to 7 pF) that is dependent on the nature of the gas. IL/MOF based sensors can detect changes in concentrations in the range of 10k-100k ppm in less than a second. The conclusions of this work are the first steps towards the development of 2D printed sensors based on IL/MOF materials. Such materials offer countless possibilities to tailor the porosity, chemistry, selectivity, and electrical response to make the sensor suitable to detect the desired analyte.

Automated summary

This paper evaluates the potential of 2D printing technologies to create thin film gas sensors from IL/MOF composites. The sensors show a rapid response to changes in gas concentration and can detect variations in the range of 10k-100k ppm in less than a second. The IL/MOF materials offer possibilities to tailor the sensor's porosity, chemistry, selectivity, and electrical response.