An ISFET sensor-integrated micromixer for pH measurements

Official URL: http://dx.doi.org/10.1109/EuroSimE48426.2020.9152729

This study reports the design and numerical modelling of a microfluidic mixer with an integrated ion-sensitive transistor (ISFET) for sensing of pH values. The valves in the microfluidic device allowed adjustment of the flow rate of each solution and different pH values for the mixture was achieved. At high flow rates around 1500 \mu \mathrm{L} /\min, pH value of the solution could be controlled in the range of 3-12 with a response time on the order of seconds. The performance of the proposed micromixer in mixing diluted acid and base solutions was simulated using COMSOL Multiphysics software. Current-voltage characteristics were obtained by using silicon dioxide (SiO2) and tantalum pentoxide (Ta2 O5) as the gate dielectric, and pH sensitivities were compared. Upon optimization of the micromixer and sensor, a numerical model, which included both components was developed by setting the flow rates of diluted acid and base solutions. This enabled active control on the pH of the mixed solution, which was exposed to the ISFET pH sensor at the outlet of the micromixer, where the ISFET sensor continuously monitored the pH of the solution with a separate readout circuit.