Gate material analysis for drift reduction in organic electrochemical transistors for biosensing

We studied the contributions to drift, a change in drain current that occurs without the presence of an analyte, in organic electrochemical transistors (OECTs) functionalized with secondary immunoglobulin (Anti-IgG) antibodies. To do so, we observed the drift response of OECTs with poly(3-hexylthiophene) (P3HT) as the charge carrier and varied the type of bio-attachment layer and the concentration of anti-IgG. Drifts could often be fit to linear equations, but more generally, they followed exponential functions on various time scales. Thinner bio-attachment layers formed by self-assembly showed the least amount of drift, while a mixture of semi-conducting polymers showed the most significant drift. Decreasing anti-IgG concentration also significantly improved drain current stability. Expected attachment and binding of anti-IgG and IgG, respectively, were verified by horseradish peroxidase-tetramethylbenzidine indicator. The optimized design of the self-assembled layer and low anti-IgG concentration showed promising detection abilities of 1 μM IgG against a control.