PHOTOSENSITIVE POLYURETHANES APPLIED TO THE DEVELOPMENT OF CHEMFET AND ENFET DEVICES FOR BIOMEDICAL SENSING

Chemical microsensors based on ion-selective held effect transistor (I SFET) transducers with ion-selective and enzymatic membranes have been fabricated. In this case, photolithographically patterned membranes b ased on acrylated urethanes have been developed and applied onto the g ate area of ISFET chips. Aliphatic urethane diacrylate has been used f or K+ and NH4+ membranes, while a photocurable hydrogel formulation ba sed on other type of acrylated urethane has been optimized for urea-FE T sensors. Resulting potassium and ammonium sensors show similar perfo rmances to those found when PVC membranes are employed. An integrated packaging process for ISFET-based sensors has been developed giving th e possibility of carrying out most of the encapsulation on wafer level . For this purpose, a photocurable polyurethane encapsulant formulatio n has been optimized to be microstructured by photolithography. Finall y, a preliminary study of biocompatibility of photosensitive formulati ons containing urethane oligomers has been performed in order to exami ne future applications in biomedical and clinical analysis. (C) 1997 E lsevier Science Limited.