Exhaled-Breath Detection Using AlGaN ∕ GaN High Electron Mobility Transistors Integrated with a Peltier Element

AlGaN/GaN high electron mobility transistors (HEMTs) integrated with a Peltier element are demonstrated for the detection of exhaled-breath condensate. The Peltier element mounted on the back side of the AlGaN/GaN HEMT was used to lower the temperature of the sensor in order to condense the exhaled breath. The measured current change shows that the pH of the condensate from the exhaled breath is within the range of 7-8, corresponding to the range of interest for human blood. The sensor exhibited a repeatable change of 1.24 mA/mm of the drain current at a drain bias of 0.25 V when the surface was exposed to repeated exhalations. This demonstrates the possibility of using AlGaN/GaN HEMT-based technology for the investigation of airway pathology.