Figure 5. The time evolution of the drain current I_ds for CTAB.

(a) and Adrenaline (b) for a fixed V_gs = 0.8 V.A direct comparison between CTAB and adrenaline is presented in (c) for the micro electrode #3, that is, the center of the device. The inset in (d) unveils the different time dynamics between CTAB and adrenaline for a specific time interval 300–380 s. For CTAB, the micro sensor behaves as if the output conforms to the standard curve of a second-order response. Differently, when considering adrenaline, the time-dependent characteristic of the system resembles that of a first order system. The described trend is generally repeated for all the micro-electrodes from #1 to #5 in line on the device (e).