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@PHDTHESIS{Liang:772868,
author = {Liang, Yuanying},
othercontributors = {Offenhäusser, Andreas and Pich, Andrij},
title = {{I}nterdigitated organic electrochemical transistors for
biosensing},
school = {RWTH Aachen University},
type = {Dissertation},
address = {Aachen},
reportid = {RWTH-2019-10802},
pages = {1 Online-Ressource (VIII, 109 Seiten) : Illustrationen,
Diagramme},
year = {2019},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University 2020; Dissertation, RWTH Aachen University, 2019},
abstract = {The development of transistors with high gain is crucial
for applications where extracellular potentials of
electrogenic cells or chemical signals are recorded. Organic
electrochemical transistors (OECTs) have recently emerged as
versatile electrophysiological sensors due to their distinct
advantages compared to other sensing systems, including
direct communication via ions between the conducting polymer
channel and electrolyte, biocompatibility, transparent
channel material, and high transconductance. The
transconductance of OECTs critically depends on the
width-to-length ratio of the drain-source channel and the
thickness of organic conducting polymer. Conventional OECTs
require large channel dimensions and thick polymer film,
which results in slow operation. Therefore, in this thesis,
interdigitated OECTs (iOECTs) were developed to obtain high
transistor performance and high device density and were
utilized for biological and chemical sensing.First, the
effect of channel geometry on the electrical performance of
interdigitated OECTs (iOECTs) was investigated. A superior
device performance is achieved by systematically optimizing
the electrode layout regarding channel length, number of
electrode fingers, and electrode width. Interestingly, the
maximum transconductance (gmax) does not straightforwardly
scale with the channel width-to-length ratio, which is
different from planar OECTs. This deviation is caused by the
dominating influence of the source-drain series resistance
Rsd for short channel devices. Noteworthy, there is a
critical channel length (15 µm), above which, the channel
resistance Rch becomes dominant and the device
characteristics converge towards those of planar OECTs.
Design rules for engineering the performance of iOECTs are
proposed and tested by recording action potentials of
cardiomyocyte-like HL-1 cells with high signal-to-noise
ratio. The above results demonstrate that interdigitated
OECTs meet two requirements of bioelectronic applications,
namely high device performance and small channel dimensions.
Flexible and transparent electronic devices possess crucial
advantages over conventional silicon based systems for
bioelectronic applications since they are able to adapt to
non-planar surfaces, cause less chronic immunoreactivity,
and facilitate easy optical inspection. Therefore, the
iOECTs were embedded in a flexible matrix of polyimide to
record cardiac action potentials. The wafer-scale devices
were firstly fabricated. Considering the transfer
characteristics of iOECTs, the flexible device exhibits
transconductances (12 mS/V) and drain-source on/off ratio
(~105) comparable to state of the art non-flexible and
superior to other reported flexible OECTs. The transfer
characteristics of the device are preserved even after
experiencing extremely high bending strain and harsh
crumpling. The excellent device performance is proved by
mapping the propagation of cardiac action potentials with
high signal-to-noise ratio. These results demonstrate that
the electrical performance of flexible OECTs can compete
with hard-material-based OECTs and thus potentially be used
for in vivo application. IOECTs do not only have great
potential for recording of electrophysiological signals but
also for chemical sensing. Conventional electrochemical
aptamer receptor/transducer systems for the detection of
various kinds of targets are often limited by the low
density of receptors attached to the sensor surface and high
background signals. An iOECTs-based aptasensor is used as a
transducer to detect the light molecule (ATP) and compared
with a conventional amperometric aptasensor regarding
sensitivity and dynamic detection range. When operated as a
sensor, the OECT senses modulations of the gate electrode
potential induced by binding of the analyte to the aptamer
receptor. Even minor changes of the gate potential cause a
pronounced response of the channel current due to the
amplification characteristics of the OECT. This novel
aptasensor can selectively detect ATP with ultrahigh
sensitivity down to the concentration of 10 pM, which is
several orders of magnitude lower than the detection limit
of the same aptasensor using an amperometric transducer
principle (limit-of-detection of 93 nM) and even most of
other previously reported electrochemical sensors.
Furthermore, sensor regeneration is demonstrated, which
facilitates reusability of the aptasensor. The small device
size in combination with high transconductances paves the
way for the development of highly sensitive integrated
micro-biosensors for point-of-care applications.},
cin = {134210 / 130000},
ddc = {530},
cid = {$I:(DE-82)134210_20140620$ / $I:(DE-82)130000_20140620$},
typ = {PUB:(DE-HGF)11},
doi = {10.18154/RWTH-2019-10802},
url = {https://publications.rwth-aachen.de/record/772868},
}
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