Live demonstration: Real-time chemical imaging of ionic solutions using an ISFET array

We demonstrate a CMOS-based lab-on-chip platform which is capable of ion imaging to detect a variation in hydrogen, potassium and sodium ions. An ISFET array is used to detect a change in ion concentration with a calibration scheme to cancel the offset due to trapped charge. The Si
₃
N
₄
passivation layer confers an inherent sensitivity to the sensors, and additional polymer membranes are pipetted containing a potassium and sodium ionophore. An initial algorithm identifies the sensitivity of each pixel towards the target ions. The user can inject a solution with a given concentration of ions and observe the real-time output change of the array on a MATLAB interface. The display then provides an estimate of the target ion concentration.