Fig. 1: Cortisol circadian rhythm and sensing principle of the extended-gate FET configuration for its measurement in a wearable patch. | Communications Materials

Fig. 1: Cortisol circadian rhythm and sensing principle of the extended-gate FET configuration for its measurement in a wearable patch.

From: Extended gate field-effect-transistor for sensing cortisol stress hormone

Fig. 1

a 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, b concept of 3D-integrated cortisol sensor embedded in a patch used as wearable on the upper arm: at the bottom, the FET gate is extended through metal vias to a top metal layer covered with aptamer-decorated graphene. The system includes a top microfluidic channel that guides the sweat (LUT) over an integrated planar reference electrode and the functionalized graphene. c Schematic of extended-gate FET configuration used in this work: the functionalized electrode is electrically connected to the gate of the MOSFET transducer and immersed in the measurement solution while the extended-gate electrode is biased via the voltage applied on the reference electrode.

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