The development of transistors with high gain is essential for applications ranging from switching elements and drivers to transducers for chemical and biological sensing. Organic transistors have become well-established based on their distinct advantages, including ease of fabrication, synthetic freedom for chemical functionalization, and the ability to take on unique form factors. These devices, however, are largely viewed as belonging to the low-end of the performance spectrum. Here we present organic electrochemical transistors with a transconductance in the mS range, outperforming transistors from both traditional and emerging semiconductors. The transconductance of these devices remains fairly constant from DC up to a frequency of the order of 1 kHz, a value determined by the process of ion transport between the electrolyte and the channel. These devices, which continue to work even after being crumpled, are predicted to be highly relevant as transducers in biosensing applications.

Transistors with tunable transconductance allow high-quality recordings of human brain rhythms.

In this Perspective, we make the case that the biological applications of organic semiconductor devices are significant. Indeed, we argue that this is an arena where organic materials have an advantage compared to traditional electronic materials, such as silicon. By discussing the physical structure and morphology of conjugated polymers, we are able to emphasize the key properties that make organic materials ideal for bioelectronics applications. We highlight a few recent devices that show either unique features or exceptionally high performance. On the basis of these examples, we discuss the future trajectory of this emerging field, note areas where further research is needed, and suggest possible applications in the short term.

The rising field of bioelectronics, which couples the realms of electronics and biology, holds huge potential for the development of novel biomedical devices for therapeutics and diagnostics. Organic electronic devices are particularly promising; the use of robust organic electronic materials provides an ideal biointerface due to their reported biocompatibility, and mechanical matching between the sensor element and the biological environment, are amongst the advantages unique to this class of materials. One promising device emerging from this field is the organic electrochemical transistor (OECT). Arguably, the most important feature of an OECT is that it provides local amplification and as such can be used as a high fidelity transducer of biological events. Additionally, the OECT combines properties and characteristics that can be tuned for a wide spectrum of biological applications. Here, we frame the development of the OECT with respect to its underlying optimization for a variety of different applications, including ion sensing, enzymatic sensing, and electrophysiology. These applications have allowed the development of OECTs to sense local ionic/biomolecular and single cell activity, as well characterization of tissue and even monitoring of function of whole organs. The body of work reviewed here demonstrates that the OECT is an extremely versatile device that emerges as an important player for therapeutics and diagnostics.

This is the first ever demonstration of an accumulation mode OECT for biosensing and n-type polymer in electrocatalysis.

The emergence of organic electronics represents one of the most dramatic technological developments of the past two decades. Perhaps the most important frontier of this field involves the interface with biology. The “soft” nature of organics offers better mechanical compatibility with tissue than traditional electronic materials, while their natural compatibility with mechanically flexible substrates suits the nonplanar form factors often required for implants. More importantly, the ability of organics to conduct ions in addition to electrons and holes opens up a new communication channel with biology. In this article, we consider a few examples that illustrate the coupling between organic electronics and biology and highlight new directions of research.

The bulk of the currently available biosensing techniques often require complex liquid handling, and thus suffer from problems associated with leakage and contamination. We demonstrate the use of an organic electrochemical transistor for detection of lactate (an essential analyte in physiological measurements of athlete performance) by integration of a room temperature ionic liquid in a gelformat, as a solid-state electrolyte.

The integration of an organic electrochemical transistor with human barrier tissue cells provides a novel method for assessing toxicology of compounds in vitro. Minute variations in paracellular ionic flux induced by toxic compounds are measured in real time, with unprecedented temporal resolution and extreme sensitivity.