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Conducting and Conjugated Polymers for Biosensing Applications
Published in John R. Reynolds, Barry C. Thompson, Terje A. Skotheim, Conjugated Polymers, 2019
C. Pitsalidis, A.M. Pappa, C.M. Moysidou, D. Iandolo, R.M. Owens
The use of a polymeric material as the active component of a transistor was first established by Wrighton et al., who, in the early 1980s, developed the so-called organic electrochemical transistor (OECT).31 However, at the time no specific application was proposed. Since then, polymer transistor technology has entered the biomedical arena as an especially promising tool due to its miniaturization and facile integration into portable electronic devices. Additionally, as the main advantage of a transistor is its ability to amplify and control the input signal, transistors have proven to improve sensitivity in biosensing compared to passive electrodes. Electrolyte-gated (polymeric) transistors (EGPTs) have so far dominated in CP biomedical applications, due to their fundamental mode of operation that uses the electrolyte as a component of the gate electrode. EGPTs are three-terminal devices in which two electrodes, the source and the drain, are connected via a conducting polymer and the third electrode, the gate, is separated from the polymer by an electrolyte, directly determining the current that flows in the channel of the transistor.7,32 Because an aqueous electrolyte solution is the natural environment for biological receptors, such polymeric transistors are compatible with biological reactions and components. To date, two main types of EGPTs exist, those that rely on the capacitive double-layer formation at the electrolyte–channel interface (field effect) and the OECTs that rely on the bulk interactions between the electrolyte ions and the transistor channel (Figure 23.4).7
Perspective on the Advancements in Conjugated Polymer Synthesis, Design, and Functionality over the Past Ten Years
Published in John R. Reynolds, Barry C. Thompson, Terje A. Skotheim, Conjugated Polymers, 2019
Brian Schmatz, Robert M. Pankow, Barry C. Thompson, John R. Reynolds
While electrochemically prepared polyaniline and polypyrrole were used for biosensing applications in the 80s and 90s, greater control over polymer synthesis has led to a rebirth in the area of conjugated polymer bioelectronics. The main efforts in this area center around an organic electrochemical transistor (OECT), which is a type of biosensor that translates ionic flux in biological media to changes in transistor current, and the organic electronic ion pump, which can be used to regulate flow of ions.[123] Both of these devices rely on the active material’s ability to transport both electronic and ionic charges, and so work over the next decade will seek to find ways to modify high charge mobility conjugated polymers to also exhibit ionic transport. As mentioned in the side chain engineering section of this chapter, oligoether side chains have been used to promote ionic interactions in conjugated polymers for OECT applications, but there are still many possibilities to explore in terms of both side chain and backbone modification to enhance ionic transport. Outside of bioelectronics, conjugated polymers are promising materials for tissue engineering and imaging applications. Soft materials are ideal for replicating tissue, but not many soft materials are electroactive. Conjugated polymers can bridge this gap, and have been used for cell scaffolding applications where oxidation of the polymer leads to more effective cell growth and differentiation.[124] For imaging applications, conjugated polymers can be engineered for high fluorescence, biocompatibility, and potentially specific binding to analytes through side chain modification.[125]
Medical textiles
Published in Textile Progress, 2020
Organic electrochemical transistors (OECTs) are devices composed of a stripe of conductive polymer that works as a channel and another electrode that works as a gate. Between them is an electrolyte solution. The channel current can be modulated by the gate voltage through electrochemical reactions that change the charge-carrier concentration in the transistor channel material and thus alter the conductivity of the channel. An OECT was developed which consisted wholly of the flexible conductive polymer PEDOT:PSS [658] and this was screen-printed onto/embedded into a flexible fabric made of woven cotton/Lycra® to enable the non-invasive monitoring of biomarkers in external body fluids [669, 670].