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Please send examples of research projects being conducted in the lab to lab staff for inclusion on this page.
THz and Millimeterwave Metamaterials
The THz and millimeterwave metamaterials are fabricated successfully
at wafer scale on flexible substrates. The metamaterials are
fabricated on different flexible substrates using standard deep UV
photolithography patterning, gold metalization and liftoff process.
The critical dimension is 15 um.
Floating Element Surface Shear Sensors
Floating element surface shear force sensors are under
development for aerospace applications. These sensors detect surface
shear by measuring a capacitance change for a deflecting shuttle.
The sensors under development include active feedback control for
rebalancing of the shuttle in an effort to extend dynamic range,
reduce nonlinearities, and reject disturbances. With Spirit
Flexible Parylene-based Microelectrode Arrays
A flexible multi-electrode array intended for high resolution
electromyographic (EMG) recordings has been fabricated using
Parylene C as substrate material. The fabrication protocol comprises
vapor deposition of parylene C, standard photolithography,
sputtering deposition and reactive ion etching. The thickness of the
final devices is <20μm, while the radius of the recording electrodes
is 40μm. The devices have been successfully tested in vivo in the
model system Manduca sexta.
Hair-like Surface Shear Force Sensors
MEMS shear sensor and shear sensor arrays for surface shear force
measurement are under development. The shear sensor consists of 80
µm high SU-8 posts resting on a polysilicon base. A capacitive
sensing scheme is used for detecting the vector force applied to
this post. Different size hair-sensors and hair-sensor layouts are
designed. The sensitivity and dynamic range of each design are
computed. Predicted dynamic range is on the order of 60 dB. The most
sensitive design is expected to measure shear forces on the order of
0.1 Pa in a 500 Hz band. Fabrication combines the polyMUMPS foundry
process with post-processing at Tufts. Characterization is ongoing.
Major support from Spirit Aerosystems with additional funding from
NASA and DARPA.
Copper Nanowires for Crossed-Nanowire Transistors
Copper nanowires (with a thin copper oxide sheath) were grown on
a silver substrate for use as the gate in experimental crossed-nanowire
transistors. The nanowires are grown by the electroplating of copper
through anodized aluminum templates, which were later etched. The
nanowires are ~150nm in diameter and 5um in length. Other potential
applications include anodes in super-capacitors, frictional
elements, and high surface area electrodes for sensing.
Micromachined Pressure Sensor Arrays for Aeroacoustics
Design, fabrication, and characterization of a surface
micromachined, front-vented, 64 channel (8X8), capacitively sensed
pressure sensor array is underway. The array was fabricated using
the MEMSCAP PolyMUMPs process, a three layer polysilicon surface
micromachining process with additional postprocessing fabrication
steps (release, packaging, Parylene coating) carried out at Tufts.
Acoustic sensitivity studies show single element acoustic
sensitivity of 0.7 mV/Pa from 200 to 20 kHz.
Lab-on-a-chip Devices for Dynamic Seeding of Bone Cells
Lab-on-a-chip devices have become increasingly popular as quick
and easy diagnostic and experimental tools due to their size,
flexibility in application, and relative ease of manufacturing and
use. The development of customizable lab-on-a-chip features, such as
surface patterning or coatings, can have widespread application.
This research established low-cost and simple calcium phosphate
coating capabilities on a silicon wafer using electrophoretic
deposition, as well as the ability to pattern such a coated wafer
with photoresist. The coated and patterned wafer was used to
evaluate the ability of bone cells to adhere to a microchannel
surface under flow, or dynamic seeding conditions.
Micromolding of Aqueous-Derived Silk Structures
There is enormous potential for biopolymers in MEMS applications.
In MEMS devices biopolymers could function as membranes or optical
components. Devices which demand outstanding biocompatibility, such
as implantable sensors, could be packed in or fully manufactured
from biopolymers materials. The challenge today exists in
understanding critical processing parameters in manufacturing
structures with micron and submicron level features from
biopolymers. In this research, the development of a micromolding
technology, to produce microstructures from aqueous derived silk
solutions is studied. In particular, well-defined cellular and
tissue culture substrate (scaffold) fabrication is used as a model
to study manufacturing methods. The manufacturing challenges consist
in counteracting shrinkage caused by solvent evaporation, producing
well defined porous structures and demolding of delicate structures.
Microfabricated Perfusion System for Vascularized Tissues
There is a critical clinical demand for tissue-engineered,
three-dimensional constructs for tissue repair and organ
replacements. Upon initial implantation, three-dimensional (3-D),
tissue-engineered (TE) constructs maintain functionality and
interface with the human body. In the long-term, however, necrosis
occurs at the core of the construct because of limited oxygen and
nutrient diffusion into the deeper layers of the TE construct. The
diffusion limit of oxygen and nutrients into 3-D TE constructs is a
major obstacle in the tissue engineering field. The clinical success
of future 3-D TE constructs depends on developing the capability to
deliver nutrients to larger systems.
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