Active Operation State Optimization of OECTs by Extremum Seeking Method Based on Amplitude Feedback

Organic electrochemical transistor (OECT) based biosensors have gained extensive research interest due to their high transconductance, low driving voltage, and biocompatibility. However, unlike conventional transistors, OECTs often suffer from inferior stability in device performance, such as degradation and drift in current. Here, an extremum-seeking method based on amplitude feedback to regulate the static operating point of OECTs is proposed to actively maintain the OECTs to work within their optimal condition. The method obtains the estimated amplitude of the acquired signal in the control period through Kalman filtering as a feedback parameter and performs a step-by-step search according to the slope change of the amplitude. Thereafter, the optimal operating point of the OECT is located. It is demonstrated that by adopting such a method, the performance degradation of OECT sensing units in continuous operation of OECT along with a miniature sensing system can be effectively alleviated. Taking the ECG (electrocardiogram) test as an example, this method has effectively suppressed the R-peak amplitude decline by 15% when compared with that in an uncontrolled situation. Such performance is comparable to that of the control of the traditional scheduled scan method. Moreover, it overcomes the defect where the scheduled scan method must suspend and rescan every working period and enables the adjustment on the working point of the OECT sensor in a long-term continuous monitoring status without additional operation. This study provides a solution for OECT to maintain performance stability in continuous sensing and monitoring, which may facilitate the further commercialization of OECT-based sensors and sensing systems.