Integrating an Enzyme‐Entrapped Conducting Polymer Electrode and a Prereactor in a Microfluidic System for Sensing Glucose

In this study, the flow injection analysis was applied to the enzyme‐entrapped electrode on a chip for sensing glucose. The on‐chip microelectrode was fabricated by the standard photolithography in clean‐room environment and the microfluidic channel height of 100 μm on the chip was formed by poly(dimethylsiloxane). The conducting polymer, poly(3,4‐ethylenedioxythiophene), PEDOT, was electropolymerized to entrap the coexisting glucose oxidase (GOD) by cyclic voltammetry (CV). The amount of enzyme entrapped in the matrix measured spectroscopically was about 0.101 U/cm2. At a flow rate of 10 ml/hr, the working electrode (Pt/PEDOT/GOD, WE1) was set at 0.7 V (vs. Ag/AgCl) and sensing of H2O2 was carried out by injecting samples with various concentrations of glucose (Glu). A linear relationship between the sensing current and the glucose concentration, ranging from 1 to 20 mM, was obtained with a sensitivity of 8 nA mm−2 mM−1. The response time and the recovery time were about 30 and 230 s, respectively. For a single‐potential test, the oxidation currents of 0.08 mM ascorbic acid (AA) and a blend of 0.08 mM AA and 10 mM Glu reached 31.3% and 145.5%, respectively, when compared with the oxidation current of 10 mM Glu alone. However, when a pre‐reactor (WE2) was set at the same potential (0.7 V) before the main enzyme integrated electrode (WE1), the oxidation current for the above mixed solution reached 99.6% of the original one.