Expansion of a linear range of the ion-concentration measurement system using microfluidic device with ISFET sensors

We have previously reported a pH measurement device using a microfluidic technology and ion-sensitive field-effect transistor (ISFET). The device has successfully measured pH values, however the range of linearity was limited within neutral range. In this paper we have evaluated the linearity of the sensor signal with a wide range of pH. The present device obtained high linearity in the range of pH 1-10 with the correlation factor of 0.9985. The averaged measurement error and standard deviation were -0.0083 and 0.0085 pH, respectively.