Figure 1
From: A Disposable paper breathalyzer with an alcohol sensing organic electrochemical transistor

Concept of the OECT-breathalyzer.
(A) Simply breathing on the printed PEDOT:PSS OECT allows for alcohol detection. (B) The alcohol dehydrogenase (ADH) enzyme and the OECT are the key components of the sensor. The OECT is printed on paper and comprises a channel, source (S), drain (D) and gate (G) electrodes made of PEDOT:PSS. The enzyme electrolyte gel is deposited to the OECT bridging the channel and gate. (C) Id response of the OECT upon exposure to ethanol.