Figure 18.

(a) Recognition of verbal commands by moisture patterns of exhaled breath air. Courtesy: Adapted with permission from ref. [111]. Copyright 2021 American Chemical Society. (b) Response with a bare hand vertically approaching and retracting away from the surface. A hand with a glove does not affect the current intensity. Courtesy: Adapted with permission from ref. [70] Copyright 2017 American Chemical Society. (c) A flexible humidity sensor applied to human skin to test skin moisture. (d) Variation in facial water contents under different conditions of the subject: waking up, drinking, washing face, and moisturizing face by moisturizer. Courtesy: Adapted with permission from ref. [170]. Copyright 2017 Wiley.