Fig. 3. Highly integrated sensing chip with all three ISMs.

a Schematic of the fully integrated ion sensing chip with all three ISMs (right) and corresponding color map showing the Dirac Point of each sensing unit. The average Dirac Point prior to functionalization is 0.15 ± 0.04 V. White pixels indicate nonfunctional cells due to the fabrication process b I–V characteristics of devices on an integrated sensing chip measured in an electrolyte solution containing 100 μM K⁺, 30 mM Na⁺ and 1 mM Ca²⁺ ions. The solid line is the average I–V characteristic and shaded region indicate an error band of plus or minus one standard deviation. Different colors indicate sensors functionalized with different ISMs. c Dirac Points of the integrated sensing chip in solution containing various Na⁺ ion concentrations. Error bars indicate plus or minus one standard deviation of the Dirac Points of all the working devices on the chip. d Principal component analysis (PCA) of the integrated sensing chip towards electrolytes comprised of different of ions using Dirac Points as feature vectors.