Hartung-Gorre Verlag
Inh.: Dr.
Renate Gorre D-78465
Konstanz Fon: +49 (0)7533 97227 www.hartung-gorre.de
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Scientific Reports on Micro and Nanosystems
edited by Christofer Hierold
Vol. 39
Signe Lin Kuei Vehusheia
Exploring heat flux
as a marker
for the early detection of
infection
1st Edition 2025. (8), XXXII, 214 pages. € 64,00.
ISBN 978-3-86628-835-5
Abstract
The
exceptional properties of carbon nanotubes (CNTs), including their high
mechanical strength, electron mobility, and thermal conductivity, make them
promising candidates for various applications. One possible application is the
sensing of nitrogen dioxide (NO2), a toxic
pollutant with significant implications for air quality monitoring, pollution
control, and medical applications. Existing sensor technologies often fail to
meet the stringent requirements for power consumption, shelf life, readout
speed, and limit of detection (LOD) necessary for mobile applications. CNT-based
gas sensors offer substantial potential to address these limitations, yet several
challenges must be overcome to utilize their full potential.
One major
technological hurdle is the high-volume fabrication of CNT devices, in
particular that of suspended CNT devices, which demonstrate several advantages
as sensors. This thesis presents an approach to address this challenge,
focusing on the scalable batch growth of suspended CNTs and their automated
assembly into functional devices. Through systematic multi-parameter
optimization and the development of large-scale growth substrates, the optimal
growth conditions for CNTs were identified, leading to a significant increase
in the number of individual CNTs available for device integration. An automated
nanoassembly machine was employed to transfer
pre-selected CNTs from growth substrates to device substrates.
The process
flow designed around automated robotic assembly demonstrates a production rate
– mechanical transfer rate for carbon nanotubes – of approximately 46 CNTs per
hour, with a 70 % yield of electrically active devices. The assembled devices
were characterized electrically to understand the performance of devices
fabricated by this method.
Contact
resistance at the CNT-electrode interface is another critical factor influencing
device performance. This thesis demonstrates that electrode etching with argon
ion immediately prior to nanotube transfer effectively removes all adsorbates
from palladium or gold electrode surface and, as a result, consistently enables
clean CNT-electrode contact. When combined with post-transfer thermal
annealing, this pre-transfer treatment reduces the median ON-resistance (Ron) of CNT
devices by an order of magnitude and the interquartile range by more than two
orders of magnitude. This is crucial for the self-heating functionality of
suspended CNT gas sensors.
Lastly, the thesis demonstrates the application of
suspended CNTs in fast and ultra-low-power NO2 sensors. By
leveraging self-heating for rapid gas desorption and employing a nonlinear
transient analysis method, the sensors achieved a signal recovery time of 1
minute and readout time of 1-5 minutes at a peak power of approximately 5.6 μW. With a
readout time of 5 minutes, the limit of detection of the sensor was 9 ppb NO2 in synthetic
air with 40 % relative humidity. These performance improvements were reproduced
with additional devices, which were assembled both manually and automatically.
Keywords: microfluidics, in vitro diagnostics, chip microcalorimetry,
infectious markers, implant sensing
Scientific Reports on Micro and Nanosystems
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Hartung-Gorre
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