Organic Thin Film Transistors in Biological Sensing Applications

Abstract

Organic thin film transistors (OTFTs) promise low cost, rapid, and specific detection of a variety of analytes. Biosensors are a broad category of detection devices that relate to the use of biological materials in sensor applications or in detection of those materials themselves. The largest commercial use for biosensors currently is in end user focused devices. These include the lateral flow pregnancy test, electrochemical glucose sensors, and the recent high profile lateral flow rapid COVID test. Typical OTFT based biosensor devices function by responding to analyte-based stimuli. A target compound is detected by a change in electrical performance metrics such as charge carrier mobility, threshold voltage, or on/off ratio. Sensor response depends on inherent material characteristics, physical device architecture, and characterization environment. While many promising proof of concept OTFT biosensors have been shown, there still remains many issues hampering their widespread adoption and commercialization including operational stability, structure-function understanding, sample introduction, and reproducibility and reliability. The work presented in this thesis tackles some of these challenges. The first N-type DNA OTFT biosensors are developed, and used to explore and understand the differences between P & N-type sensors operating at elevated temperatures. The performance of seven different P-type metal phthalocyanine based OTFTs operating at elevated temperatures are investigated and demonstrate how different material and film characteristics can impact temperature sensitivity. An OTFT-microfluidic interface was developed to facilitate more controlled sample introduction and improve capabilities in sensor investigations. Finally, a new characterization system was developed to enable thorough, productive, and flexible OTFT research investigations into OTFT biosensors. The work reported herein enables the improved and continued development of OTFT based biosensor devices towards wider adoption.