Multimode microwave sensors for microdroplet and single-cell detection
Author
AydoÄŸmuÅŸ, Hande
Advisor
Hanay, Mehmet Selim
Date
2018-08Publisher
Bilkent University
Language
English
Type
ThesisItem Usage Stats
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Abstract
A novel detection mechanism which can reveal both morphological and electrical
properties of analytes are needed for Lab-on-a-Chip applications. Herein, a
label-free, real-time and non-contact detection paradigm in microwave domain
is constructed, by using rst and second electromagnetic modes of a microwave
resonator. As the resonator, microstrip line is chosen since it o ers accessible
boundary conditions. In order to deliver the analytes into the sensing region, micro
uidic channels are fabricated. As a proof-of-concept, while the microstrip line
resonator's rst and second modes are tracked simultaneously, analytes are delivered
through the microchannel embedded underneath the signal layer. As the
analytes, water microdroplets in oil, cervical (HeLa) and breast (MDA-MB-157)
cancer cells in their appropriate medium are used and detected; their position
and electrical volume informations are obtained and compared. Allan Deviation
of the measurement is smaller than 2 108 for both modes, and due to analyte
properties in microwave domain, such as the great permittivity di erence between
the biological analyte and medium, detection is possible.
In order to test the accuracy of nding the position of the analyte, two di erent
microchannel geometries are designed. The rst geometry is based on a zigzag
channel, where microstrip line crosses the channel at 6 di erent locations. Secondly,
a branched channel is designed, to send the microdroplets at four di erent
locations. This delivery mechanism is mostly based on the hydraulic resistance:
Each droplet chooses its path by the hydraulic resistance that is caused by the
previous droplet. Hence, microdroplets are distributed to four channels. Due to
the mode shape of the speci c mode, when analyte passing through these regions,
it induces di erent frequency shifts. For these applications, micro
uidic part is
fabricated by conventional soft lithography methods, and the material for the
microchannels is PDMS. Electrical volume of the droplets is also obtained. After the usage of prototypes for position and electrical volume calculations,
second generation devices are fabricated. Compared to the PDMS-based devices,
these devices o er rapid and low-cost prototyping. Additionally, Kapton is chosen
for the dielectric material, and it has some material-wise bene ts, such as the
tangent loss level. Analytes are delivered through the sensing region by capillary
tubings, hence soft lithography steps can be eliminated. Due to the equipment
limitations, only the rst mode is tracked with these novel devices, while another
type of breast cancer cells (SK-BR-3) are delivered through the sensing region.
Signal-to-noise ratio, when compared to the PDMS based devices, is improved.
In this work, the rst two modes of microstrip line resonators are used. However,
by using higher order modes, more properties about the particles as skewness,
geometrical volume, orientation, and composition can be obtained. These
informations can be used to construct a global image of the analyte; rather than
a pixel by pixel image. Additionally,
ow cytometry applications, detection of
Circulating Tumour Cells and applications for long term cultivation on chip (also
known as Organ-on-Chip platforms) can be achieved.
Keywords
Microwave ResonatorsMicro uidics
Lab-on-a-Chip Applications
Biosensors
Multimode Detection