Figure 1.

An alkane sensor inside a breath-in prototype. The sensor consisted of a chemiresistive film (black spot on the small piece of printed circuit board) and a printed circuit board with copper wires soldered on it. The chemiresistive film was made up of tetracosane and carbon powder and was deposited on top of the circuit board within an area of 5 mm × 10 mm, connecting two copper electrodes on the circuit board. Two copper wires were soldered to the electrodes to enable a digital multimeter to measure the resistance of the chemiresistive film. The breath-in apparatus was a 125 mL empty Vitagen^® bottle. A drinking straw was fixed at the opening of the bottle to allow transfer of exhaled breath to the sensor.