11 research outputs found
Graphene Bilayer Field-Effect Phototransistor for Terahertz and Infrared Detection
A graphene bilayer phototransistor (GBL-PT) is proposed and analyzed. The
GBL-PT under consideration has the structure of a field-effect transistor with
a GBL as the channel and the back and top gates. The positive bias of the back
gate results in the formation of conducting source and drain sections in the
channel, while the negatively biased top gate provides the potential barrier
which is controlled by the charge of the photogenerated holes. The features of
the GBL-PT operation are associated with the variations of both the potential
distribution and the energy gap in different sections of the channel when the
gate voltages and the charge in the barrier section change. Using the developed
GBL-PT device model, the spectral characteristics, dark current, responsivity
and detectivity are calculated as functions of the applied voltages, energy of
incident photons, intensity of electron and hole scattering, and geometrical
parameters. It is shown that the GBL-PT spectral characteristics are voltage
tuned. The GBL-PT performance as photodetector in the terahertz and infrared
photodetectors can markedly exceed the performance of other photodetectors.Comment: 7 Pages, 7 figure
Multizone Paper Platform for 3D Cell Cultures
In vitro 3D culture is an important model for tissues in
vivo. Cells in different locations of 3D tissues are
physiologically different, because they are exposed to different concentrations
of oxygen, nutrients, and signaling molecules, and to other environmental
factors (temperature, mechanical stress, etc). The majority of high-throughput
assays based on 3D cultures, however, can only detect the
average behavior of cells in the whole 3D construct.
Isolation of cells from specific regions of 3D cultures is possible, but relies
on low-throughput techniques such as tissue sectioning and micromanipulation.
Based on a procedure reported previously (“cells-in-gels-in-paper”
or CiGiP), this paper describes a simple method for culture of arrays of thin
planar sections of tissues, either alone or stacked to create more complex 3D
tissue structures. This procedure starts with sheets of paper patterned with
hydrophobic regions that form 96 hydrophilic zones. Serial spotting of cells
suspended in extracellular matrix (ECM) gel onto the patterned paper creates an
array of 200 micron-thick slabs of ECM gel (supported mechanically by cellulose
fibers) containing cells. Stacking the sheets with zones aligned on top of one
another assembles 96 3D multilayer constructs. De-stacking the layers of the 3D
culture, by peeling apart the sheets of paper, “sections” all 96
cultures at once. It is, thus, simple to isolate 200-micron-thick
cell-containing slabs from each 3D culture in the 96-zone array. Because the 3D
cultures are assembled from multiple layers, the number of cells plated
initially in each layer determines the spatial distribution of cells in the
stacked 3D cultures. This capability made it possible to compare the growth of
3D tumor models of different spatial composition, and to examine the migration
of cells in these structures