Most organic electrochemical transistor (OECT)-based biosensors currently rely
solely on the generation of electronic signals upon sensor-analyte interaction which has
limited the range of analytes to those with distinct electronic properties or those that rely
on specific biological materials with poor environmental stability, such as redox enzymes
and antibodies. The development of durable stimuli-responsive hydrogels, which exhibit
changes in ionic conductivity upon interacting with specific analytes, has significantly
expanded the potential for ionic-based sensing as an alternative to electronic-based
sensing. Although OECTs are suitable for measuring ionic signals, there have been only
a few instances where these materials have been utilized within an OECT platform.
This study investigates the applicability of OECTs for ionic-based sensing using
poly(vinyl alcohol) (PVA) hydrogels and PEDOT:PSS based OECTs. Through varying
macromer percentage alone, a set of hydrogels was fabricated that mimics the network
properties seen in complex analyte-responsive systems. These hydrogels offer a cheap
alternative, without the use of biorecognition elements, for probing OECT sensitivity to
ionic signals. A system based on four electrode impedance spectroscopy was also
developed to independently measure their ionic conductivity, with preliminary results
consistent with values reported in literature.
To enhance device reproducibility and improve compatibility with hydrogel
deposition, a novel OECT geometry was designed. This involved incorporating larger
features such as wider channels and thicker electrode contacts to minimize fabrication
artifacts which ultimately improved OECT transconductance. Additionally, the impact of
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direct polymerization of hydrogels on PEDOT:PSS was explored using Raman
spectroscopy. The findings revealed that a high degree of adherence between the
hydrogel and PEDOT:PSS may significantly reduce the dedoping capacity of
PEDOT:PSS. Overall, this work represents a valuable first step in exploring the suitability
of OECTs to ionic flow based sensing using hydrogels.Open Acces
