Figure 1.

Experimental setup: (a) skin- and breath-borne volatiles of entrapped volunteers accumulate in a plethysmographic chamber. (b) The sensor array consists of three chemoresistive sensors, Si-doped MoO₃, Si-doped WO₃, and Ti-doped ZnO to monitor ammonia, acetone, and isoprene, respectively, together with commercial humidity and CO₂ sensors. Simultaneous SRI-TOF-MS measurements were used for cross-validation. (c) Image of a single sensor. (d) The sensing elements consist of highly porous and semiconductive films formed by direct flame deposition of agglomerated/aggregated metal-oxide nanoparticles, as shown by (e) top-view scanning electron microscopy exemplarily for Ti-doped ZnO.