The Performance of Commercial pH-Sensitive Ion-Selective Field Effect Transistors

pH-sensitive ion-selective field effect transistors (ISFETs) are commercially available nowadays, offering high robustness, resolution, accuracy, and durability. A crucial drawback is their high price and permanent power demand. Incorporating commercially available small-sized ISFET sensors into battery-powered devices requires a thorough evaluation and the development of strategies to reduce power consumption. In this work, a direct comparison of three different commercial ISFETs is presented using a newly developed evaluation process that aims to investigate long-term performance. The different behaviors in conditioning, linearity, accuracy, response times, and long-term stability in detail are discussed. Furthermore, strategies to decrease power consumption are presented by adjusting the operating conditions and introducing an OnOff-protocol. It is found that all ISFETs have limitations in their overall performance with the best performers being 1) Winsense, with the highest slope of 59.7 mV pH^-1; 2) Microsens, with the highest potential output precision under the recommended working point conditions (±0.01-0.03 pH) with SD and reduced working conditions (± 0.01 pH) with WD; and 3) Sentron, with the highest stability under both power-reducing strategies. With the combination of both power-reducing strategies, the ISFET's power demand is reduced by 98.8%.