Figure 16.

Examples of continuous electrochemical sensing modalities including (a) ion-selective/potentiometric, (b) enzymatic/amperometric where RE is reference electrode, CE is counter electrode, and WE is the working electrode, and (c) simple representation of aptamer-based sensing. Only (a) and (b) have been demonstrated in non-invasive wearable sensors while (c) has only been demonstrated in invasive sensing formats (in circulating blood¹⁶⁵). Generally the detection ranges are mM’s for (a), down to μM’s for (b) and down to nM’s for (c).