Different hydrophobic polymers were used for chemical modification of ion-sensitive field effect transistors (ISFETs) in order to prepare a reference FET (REFET). Chemical attachment of the polymer to the ISFET gate results in a long lifetime of the device. Properties of polyacrylate (polyACE) REFETs are described in detail. The polyACE-REFET is superior to other polymer modified REFETs, showing an excellent pH insensitivity (1 mV pH−1), a long lifetime and an electrically identical behaviour as an unmodified pH ISFET or a cation-selective PVC-MEMFET (membrane FET). The cation permeselectivity of the polymer can be significantly reduced by addition of immobile cations. The applicability of a polyACE-REFET in differential measurements with a pH ISFET and a K+ MEMFET is demonstrated.
Skowronska-Ptasinska, M., van der Wal, P. D., van den Berg, A., Bergveld, P., Sudholter, E. J. R., & Reinhoudt, D. N. (1990). Reference field effect transistor based on chemically modified ISFETs. Analytica chimica acta, 230, 67-73. https://doi.org/10.1016/S0003-2670(00)82762-2