Inkjet-printed Solid-state Potentiometric Nitrate Ion Selective Electrodes for Agricultural Application

In this work, we demonstrate a low-cost and flexible solid-state ISE (ion selective electrode) using inkjet-printing for in-field nitrate detection. Three types ISEs of 25, 50, and 140 μm thick ISM (ion selective membrane) are fabricated and characterized. The ISEs exhibit ISM thickness dependent conditioning and stability that thicker ISM leads to longer conditioning but smaller drift; and the converse is true. Whereas, all ISEs present 50-52 mv/dec sensitivity in a wide range of 0.0001M to 0.1M nitrate and ~95% accuracy in soil nitrate detection. The analytical characterizations establish a relationship between fabrication parameters (ISM thickness) and ISE performance, which can be used to tune ISE to different agricultural applications.