Integrating an Extended-Gate Field Effect Transistor in Microfluidic Chips for Chloride and Thiocyanate Potentiometric Detection

In the last five years, the development of sensors based on Extended Gate Field Effect Transistors has grown by at least 223%. In this article we discuss the concepts involved behind the potentiometric response resulting from the use of EGFETs in recognizing chloride and thiocyanate ions. The results are discussed considering two ways of obtaining the response: current modulation between source-drain and the variation in threshold voltage caused by the different concentrations of the solutions. The current sensitivity for chloride was 0.0330 mA0.5 mol-1 L and 0.1762 mA0.5 mol-1 L for thiocyanate, the linear response ranged from 1.0 to 1.0x10-5 mol L-1 for both static and dynamic setups with R2 of 0.9952 and 0.9992. The voltage sensitivity was 47.4 mV dec-1 and 52.96 mV dec-1 with R2 of 0.9999 for chloride. For the thiocyanate detection, the linear range from 1.0 to 1.0x10-5 mol L-1 with 58.88 mV dec-1 and 137.06 mV dec-1 to voltage sensitivity, with R2 of 0.9862. The voltage sensitivity obtained with the plug injection system was 170.78 mV dec-1 ranging from 1.0 mol L-1 to 1.0x10-4 mol L-1, with a R2 of 0.9436. From our knowledge, this is the first demonstration of integration of EGFETs to a 3D-printed microfluidic device in recognizing chloride and thiocyanate ions.