ION SENSOR WITH PHOTOCURABLE POLYURETHANE POLYMER MEMBRANE

A new ion-selective membrane composition for ion sensors based on alip hatic urethane diacrylate oligomer is presented. The membrane can be d eposited and photolithographically structured on a wafer containing io n-sensitive field effect transistors (ISFETs). Compatibility of the po lymer matrix with various plasticizers commonly used in polyvinyl chlo ride-based ion-selective membrane formulations has been established, a nd it is shown that the membrane may hold more than 50% of different p lasticizers. The photopolymerization rate was found to be higher than for the other compositions used for this purpose. Characteristics of a n ammonium ISFET with the developed membrane are presented, the sensit ivity was found to be 55 to 59 mV per concentration decade and the ran ge of linear response was from 10(-1) to 5 . 10(-5)M NH4Cl.