Chemical to Electrical Transduction using Fuel Cell Powered Organic Electrochemical Transistors
semanticscholar(2020)
摘要
Electrochemical
transistors have recently gained significant attention in the field of
bioelectronics. In particular, the organic electrochemical transistor (OECT), a
device that employs organic semiconductors as the active material, has been
widely investigated as biosensors due to their low operational potentials, ability
to operate in aqueous environments, biocompatibility, and the amplification of low-lying
biological signals owing to the OECTs’ large transconductance. As such, OECTs
have been utilized as biochemical sensors for monitoring of biomarkers or
metabolites, with potential application for health monitoring for wearable
devices in combination with internet of things (IoT).
The current working
principle of biosensors based on OECTs relies on the reaction between the
channel material and the analyte or intentionally generated intermediates that
undergo direct or indirect electron transfer reactions with the channel
material. This electron transfer reaction results in changes of the device
channel conductivity with respect to the concentration of the analyte in a
sample. While recent work has shown progress in development of biosensors based
on this approach, it introduces several complications and disadvantages, namely
unintended and uncontrolled chemical and electrochemical side reactions. First
and foremost, this configuration does not allow the signal amplification one
expects from a transistor device, thus invalidating the most often (and we show
here erroneously) stated advantages of using OECTs for biosensing. Further,
devices designed using this approach can rapidly degrade during the operation but
more importantly, the results and their interpretation can lead to incorrect conclusions
and render current devices unreliable for applications in health monitoring.
Our work addresses these
challenges by i) isolating the chemical reaction from the OECT channel on a
separate compartment and ii) employing enzymatic reactions to form intermediates
that drives a reaction to power the OECT. In addition, this device architecture
eliminates the need for an external gate voltage so only a single power source
is required to monitor changes of the conductivity of the OECT channel material.
Doing so also allows us to truly amplify the reaction current on the fuel
cell from µA up to mA across the OECT (with ON/OFF ratios of 104), presenting
significant improvements over conventional OECT biosensors that operate in the
nA range,
thereby eliminating the need for sophisticated measurement instrumentation. Our
work goes in depth in elucidating general materials design parameters for the fuel
cell OECT. Furthermore, the device operation mechanism was rationalized using electrochemical
and electrical measurements of a variety of state-of-the-art materials for
OECTs.
The development of this
new device architecture presents an exciting new direction for sensing of
metabolites and a low power, low cost and simple alternative approach to current
technologies. Importantly, we also challenge some of the current thinking in
the field of OECT-based biosensing. We believe that our findings will be of
great interest to researchers in the fields of bioelectronics, biofuel cells
and organic electronics. Additionally, our findings shine light on the working
mechanism of enzymatic biosensors with OECTs. We believe that our approach will
pave the way for implementation of OECT biosensors in real life applications due
to the simplification of the backend circuitry that powers and synchronizes the
gate and drain voltages.
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