A ISFET cartridge for electrolyte measurement by micromachinery

A small size cartridge is designed and fabricated for ISFET-based electrolyte sensor applications. The designed cartridge is fabricated by using micromachining techniques including silicon etching and glass bonding. Photosensitive polymer (THB 30) is used both to define a micropool and to encapsulate the sensor surface. A differential amplification method utilizing REFET (reference electrode field-effect transistor) and QRE (quasi-reference-electrode) are introduced in order to substitute the conventional Ag/AgCl reference electrode, which is unsuitable to be applied in this cartridge because of its large size. Total size of the fabricated cartridge is 2.4 cm×2.5 cm, and the dead volume of a micro flow-channel inside the cartridge is only 8.5 μl. The pH-ISFET inserted into the cartridge showed stable operation and reasonable nernstian characteristics [55 mV/pH].