AFM
Instrumentation Development
The proposed research
will focus on optimizing the performance of an atomic force
microscope (AFM) for dynamic force spectroscopy and biochemical
sensing. Although the AFM has been used extensively in these
fields of research, the performance of the instrument has been
limited by inappropriate signal processing techniques and poor
controller design. If the AFM is to reach it's full
potential as a force and mass sensing device, improvements must be
made to both the instrument and controller architecture. By
studying the AFM from a dynamic systems, measurements, and
controls approach, the resulting controllers will be tailored to
meet the process requirements of the intended application.
In doing so, the accuracy and sensitivity of the instrument can be
improved.
As part of this
research, a custom 3-axis AFM was developed, which can be seen
below. The main component of the instrument, a MultiMode AFM
head was purchased from Digital Instruments, a subsection of Veeco
Instruments Inc. The AFM head is mounted on an xy
piezoelectric stage which is suspended above the piezoelectric z
stage (both purchased from Physik Instrumente) via three high
precision adjustment screws. The instrument itself is housed
within a custom environmental chamber and Faraday cage. The
control schemes for the AFM are designed in Matlab's Simulink
environment and digitally implemented through the use of a dSPACE
DAQ card.
One of
the potential applications for an AFM-based biochemical sensor is
a diagnostic tool for the rapid determination and quantification
of disease states in patients. One of the main requirements
of such a tool would be the ability to operate in a fluid such as
blood, cerebrospinal fluid, or urine. Keeping the long-term
goal of the proposed research in mind, a key step in the
development process is to study the behavior of active cantilevers
in fluids. However, before this study can occur, a custom
fluid cell to house the cantilevers had to be designed. The
custom fluid cell designed for this research can be seen
below. The part was constructed using stereolithography, a
rapid prototyping technique that creates plastic 3-D objects form
a CAD file.
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