Two and Three Dimensional Graphene Devices for Electronics, Sensing and Biotechnology.
Kabiri Ameri Abootorabi, Shideh.
Abstract: Graphene is
an atomically thin zero band gap semiconductor or semimetal, with a strong ambipolar
electric field effect, remarkably high carrier mobility at room temperature, high
carrier density and high saturation velocity. Due to extraordinary electrical properties
of graphene, it has been suggested as a possible candidate for beyond-CMOS field effect
transistor (FET) with applications ... read moremainly in RF and analog domain. Graphene is also
mechanically strong and has good biocompatibility, is electrochemically stable, shows
excellent broadband optical transparency and can be made very sensitive to the
surrounding media, making it a promising candidate for sensing and bioelectronics
applications. Although two dimensional graphene has shown remarkable electrical,
physical and chemical properties, extending it in three dimensional form may enhance the
functionality and performance of devices and enable new functions currently not
possible. In this dissertation, the application of two and three dimensional graphene in
electronics, sensing and bioelectronics is presented. A transparent graphene based
microfluidic chip for dielectrophoretic cell trapping and lysis with graphene as
electrode is introduced and it is has been shown that graphene behaves as an
electrochemically stable electrode in the presence of high DC electric field in
biological medium. Using graphene minimizes the Faradic reaction which would otherwise
harm living cells and change the chemical and physical properties of electrolytes and
electrodes. Next for the first time a three dimensional graphene field effect transistor
is introduced and studied. The channel of this transistor is made of three dimensional
graphene foam, which is gated using ionic liquid and ionogel to realize both liquid and
semisolid state versions. Liquid and gel at the interface with the graphene forms a
double layer capacitance (EDLs) of extremely large capacitance per unit surface area
which provides an all-around electrostatic control of the transistor channel and leads
to a lower operating voltages. Due to higher surface area of the foam, the transistors
show up to 26.72 times higher current capacity than the equivalent conventional two
dimensional graphene transistors. The network structure of the foam expanded in three
dimensions leads to higher mechanical stability and results in mechanical
fault-tolerance. Higher surface area of the foam and high mechanical strength of three
dimensional graphene transistor make it interesting for sensing applications. In this
dissertation, mechanical, chemical and biological sensors are realized based on a mono
to double layer and few layers of the graphene foam. For chemical sensing, we
demonstrate its application in pH sensing directly in biological fluids. For mechanical
sensing, we present its application in sensing strain and for biological sensing, we
show its ability to capture electrically activity from electrogenic cells. The pH sensor
consists of a thin layer of HfO2 as a sensing surface was grown all-around of the three
dimensional graphene foam serving as a transistor channel. The three dimensional
graphene transistor shows higher pH sensitivity (79 mV/pH) than conventional two
dimensional graphene based sensor even in high ionic strength medium and in body fluids.
We attribute the high sensitivity and ability of sensing pH at high ionic strength media
to the three dimensional structure of the channel and existence of sensing surface
all-around the graphene channel. A strain sensor is based on few layers of the graphene
foam. Due to the three dimensional network structure of the graphene foam, this sensor
shows mechanical fault-tolerance and robustness, and also demonstrates high dynamic
range compared to the two dimensional graphene based sensors. Graphene foam based device
is also used as a scaffold for growing different types of cells and recording electrical
signal from electrogenic cells. It is shown that graphene shows good biocompatibility
and it can be used as an ideal electrode for recording the electrical activity of the
cells. These applications indicate the promise of three dimensional graphene transistor
as an all-in-one multimodal multifunctional transistor for smart biological
Thesis (Ph.D.)--Tufts University, 2015.
Submitted to the Dept. of Electrical Engineering.
Advisor: Sameer Sonkusale.
Committee: Qiaobing Xu, Swastik Kar, and Mohammad Afsar.
Keyword: Engineering.read less