Organic Electrochemical Transistors for Bio-Sensing Applications

Abstract

Organic electrochemical transistors (OECT) have been demonstrated and extensively studied as an effective platform for the design of chemical and biological electronic sensing applications, based on their advantages on low-voltage operation, good biocompatibility and interaction with aqueous medium, facile chemical modification of semiconductors and electrodes, and applicability on varied substrates including flexible plastics.[1] However, conventional OECTs are normally fabricated in the scale of millimeter or larger, resulting in a slow response time for device operation. To overcome this problem, here we develop a novel approach to miniaturize OECT by using only lithographic and magnetron sputtering technique. The channel of OECTs could be reduced to several to twenty microns therefore the speed of device response could be raised up to order of 10-5 s in aqueous medium. Due to the improvement in transient response time of the micro OECT device, alternating current (AC) is possible to be introduced for device operation. Combined with lock-in amplifier, the small AC channel signal could be precisely extracted from an extremely noisy environment, which provides the possibility to enhance the sensing capability of the OECT devices in complex situations. A new detection method is then established based on AC signal driven micro OECT. The detection limit of dopamine, an important neuro transmitter within the central nervous system, is down to 10-8 M, which is comparable to previous OECT sensor in steady current mode[2]. Furthermore, the pre waiting time to stabilize the device under the newly established AC mode is much shorter (tens of seconds) than conventional device needs (more than 600 s), indicating that the AC signal driven micro OECT could be a promising candidate for rapid sensing and diagnosis applications. In conclusion, we introduce a simple and easy-to-fabricate process for miniaturization of OECT devices to the cellular dimensions. The advantage of fast transient response makes the AC-driven micro OECT capable of in-situ cell activity monitoring and associated chemical sensing applications.