Toward a highly selective artificial saliva sensor using printed hybrid field effect transistors

Ion selective field effect transistors (ISFETs) have been widely used in the biological and environmental sensing applications. However, the rigid feature of common ISFETs blocked the real-time monitoring applications. Here, we report a feasible 3D printing method to fabricate flexible ISFETs by hybridization of printed organic ion selective electrodes and inorganic transistors. The fabricated ISFETs demonstrated high sensitivity, ranged about 100 mV/decade, towards ions such as ammonium (NH4+), potassium (K+), and calcium (Ca2+). Furthermore, the fabricated hybrid ISFETs showed their distinct selectivity from the mixture of varied interference ions as an artificial saliva. This capability provides an integrated platform for a comprehensive ion analysis by closely monitoring interrelated saliva parameters as wearable healthcare solutions manufactured by 3D printing methods.