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We summarize our recent results on material, device, and circuit structures for detection of volatile analytes in the atmosphere and proteins in aqueous solution. Common to both types of sensing goals is the design of materials that respond more strongly to analytes of interest than to likely interferents, and the use of chemical and electronic amplification methods to increase the ratio of the desired responses to the drift (signal/noise ratio). Printable materials, especially polymers, are emphasized. Furthermore, the use of multiple sensing elements, typically field-effect transistors, increases the selectivity of the information, either by narrowing the classes of compounds providing the responses, distinguishing time-dependent from dose-dependent responses, and increasing the ratio of analyte responses to environmental drifts. To increase the stability of systems used to detect analytes in solution, we sometimes separate the sensing surface from the output device in an arrangement known as a remote gate. We show that the output device may be an organic-based or a silicon-based transistor, and can respond to electrochemical potential changes at the sensing surface arising from a variety of chemical interactions. 

Abstract Operational stability and sensitivity are key issues for the practical application of organic field‐effect‐transistor (OFET)‐based sensors. Instability over time due to intrinsic device bias stress and conductance drift induced by the ambient environment can obscure responses to analytes of interest. These instabilities are well‐known hindrances to the practical application of OFET sensors. It is demonstrated for the first time that an innovative and simple two‐OFET circuit design can effectively compensate the drifts originating from bias stress and/or the environment while maintaining chemical sensitivity and increasing signal‐to‐noise ratio. This is enabled by illumination of one photosensitive OFET to compensate the drift of the other chemical‐sensing OFET, though in principle a pair of OFETs with opposing drifts generated by any mechanism could be used. The circuit, compared with individual OFET‐based sensors, achieves significantly increased environmental stability, and its enhanced response to chemical vapors is also demonstrated by detecting the representative pollutants nitrogen dioxide (NO₂) and ammonia (NH₃). This shows that OEFTs with drifts being compensated by any mechanism can lead to stabilized sensor circuits.