Schematic representation of the sensor array fabrication process and the electronic nose images. (a) Langmuir film deposition of organic semiconductor D2-Und-BTBT-Hex on a substrate with 20 transistors and its chemical structure. (b–e) Additional metalloporphyrin receptor molecules deposition and the corresponding chemical structures (TiO-TPP, Cu-TPP and Zn-TPP). (f) Device principal scheme. (g) Device component layout with analog part with an array of operational amplifiers shown in red, drain/gate voltage controlling operational amplifiers in white, DC–DC converters in green, digital part with a microcontroller and microSD-card slot in blue and USB charger/data transfer port and power management ICs in orange. (h) Photo of the device with sensor chamber with pogo pins array and reference T/RH sensor from the top.