Fig. 13

a Representative of lab-on-skin concept (reprinted with permission from Ref. [19] Copyright 2018 American Chemical Society). b Photo of the wearable system and Block diagram of the NFC powered sensing system (reprinted with permission from Ref. [1] Copyright 2019 American Chemical Society). c Qualitative depiction of regular and irregular circadian levels of the cortisol produced by the adrenal glands in human body through the day, showing the need for high time granularity measurements to capture the pulsatile nature of cortisol, and concept of 3D-integrated cortisol sensor integrated with a top microfluidic channel that guides the sweat over a planar reference electrode and bio-functionalized graphene (reprinted with permission from Ref [108] Copyright 2021 Nature)