We demonstrate a microfluidic system which applies engineering feedback principles to
control the pH of a solution with a high degree of precision. The system utilizes an extended-
gate ion-sensitive field-effect transistor (ISFET) along with an integrated pseudo-reference
electrode to monitor pH values within a microfluidic reaction chamber. The monitored
reaction chamber has an approximate volume of 90 nL. The pH value is controlled by
adjusting the flow through two input channels using a pulse-width modulated signal applied …