Organic electrochemical transistors (OECTs) have recently
attracted
attention due to their high transconductance and low operating voltage,
which makes them ideal for a wide range of biosensing applications.
Poly-3,4-ethylenedioxythiophene:poly-4-styrenesulfonate (PEDOT:PSS)
is a typical material used as the active channel layer in OECTs. Pristine
PEDOT:PSS has poor electrical conductivity, and additives are typically
introduced to improve its conductivity and OECT performance. However,
these additives are mostly either toxic or not proven to be biocompatible.
Herein, a biocompatible ionic liquid [MTEOA][MeOSO3] is
demonstrated to be an effective additive to enhance the performance
of PEDOT:PSS-based OECTs. The influence of [MTEOA][MeOSO3] on the conductivity, morphology, and redox process of PEDOT:PSS
is investigated. The PEDOT:PSS/[MTEOA][MeOSO3]-based OECT
exhibits high transconductance (22.3 ± 4.5 mS μm–1), high μC* (the product of mobility μ and volumetric
capacitance C*) (283.80 ± 29.66 F cm–1 V–1 s–1), fast response time (∼40.57
μs), and excellent switching cyclical stability. Next, the integration
of sodium (Na+) and potassium (K+) ion-selective
membranes with the OECTs is demonstrated, enabling selective ion detection
in the physiological range. In addition, flexible OECTs are designed
for electrocardiography (ECG) signal acquisition. These OECTs have
shown robust performance against physical deformation and successfully
recorded high-quality ECG signals.
In this work, a flexible resistive switching memory device consisting of S-layer protein (Slp) is demonstrated for the first time. This novel device (Al/Slp/indium tin oxide/polyethylene terephthalte) based on a simple and easy fabrication method is capable of bistable switching to low resistive state (LRS) and high resistive state (HRS). This device exhibits bistable memory behavior with stability and a long retention time (>4 × 10 s), being stable up to a 500 cycle endurance test and with significant HRS/LRS ratio. The device possesses consistent switching performance for more than 100 times bending, corresponding to desired applicability for biocompatible wearable electronics. The memory mechanism is attributed to a trapping/de-trapping process in S-layer protein. These promising results of the flexible memory device could find a way in the wearable storage applications like smart bands and sports equipments' sensors.
The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adom.201901714. Figure 12. a) The simulated modulation depth plot for different frequencies; and the comparison of experimental and simulated modulation depth at b) 0.2 THz, c) 0.6 THz, d) 0.8 THz under different pumping powers. www.advancedsciencenews.com
The development of organic electrochemical transistors (OECTs) capable of maintaining their high amplification, fast transient speed, and operational stability in harsh environments will advance the growth of next-generation wearable and biological electronics. In this study, a high-performance solidstate OECT (SSOECT) is successfully demonstrated, showing a recorded high transconductance of 220 ± 59 S cm −1 , ultrafast device speed of ≈10 kHz with excellent operational stability over 10 000 switching cycles, and thermally stable under a wide temperature range from −50 to 110 °C. The developed SSOECTs are successfully used to detect low-amplitude physiological signals, showing a high signal-to-noise-ratio of 32.5 ± 2.1 dB. For the first time, the amplifying power of these SSOECTs is also retained and reliably shown to collect high-quality electrophysiological signals even under harsh temperatures (−50 and 110 °C). The demonstration of high-performing SSOECTs and its application in harsh environment are core steps toward their implementation in next-generation wearable electronics and bioelectronics.
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