PhD Oral Defense, Ozgur Sahin

Ozgur Sahin sahin at
Fri May 20 13:58:05 PDT 2005

Dear Labmembers,

I will defend my PhD thesis this Tuesday. It is on a nanomechanical sensor
for single molecule level biomolecular recognition and material
charcterization. It involves micromachined devices, as well. I'd be happy
to see you there. Date, time, and location are given below.




Thesis title: Harmonic Force Microscope: A new tool for biomolecular
identification and material characterization based on nanomechanical

Speaker: Ozgur Sahin
Department of Electrical Engineering

Date: Tuesday, May 24th, 2005

Time: 1:30 pm  (refreshments at ~1:15 pm)

Place: David Packard Electrical Engineering Building, Room 101 (near Bytes

At the molecular level, physical and chemical properties of materials are
tightly coupled to the mechanical properties. The potential of mechanics
for interacting with matter at the nanoscale has been largely unexplored
due to lack of instruments capable of performing mechanical measurements at
nanometer length scales. On the other hand, most of the efforts have been
concentrated on the nanoscale electrical or optical measurements with the
tools available, albeit with limited sensitivity and practicality.

In this talk a new kind of a nanomechanical sensor, the harmonic force
microscope, will be presented. This tool allows sensitive mechanical
measurements at the nanoscale and single molecular level. It is based on
the atomic force microscope (AFM), an imaging instrument capable of
resolving individual atoms by measuring the force interaction between an
atomically sharp tip and a sample. I will briefly present a mathematical
study of the nonlinear dynamics of the vibrating probe of AFMs that shows
that information on mechanical properties is hidden in the weak
higher-harmonic vibrations of the probe. Then I will present special
micromachined cantilevers that enhance the higher harmonic generation by as
much as six orders of magnitude through a phenomenon I call mechanical
resonant energy transfer. These cantilevers allow us to recover the
information on the mechanical properties of materials and molecules.

With a nanomechanical sensor at hand, I investigated phase transformations
of sub micron domains of composite polymers and observed their glass
transitions. Studies on nucleic acids attached to a surface, a
configuration commonly used in DNA microarray technology, showed that the
hybridization of a single molecule can be observed with unprecedented

By providing data on chemistry and mechanics with high sensitivity and
nanometer spatial resolution, harmonic force microscopy has the potential
to enable a new class of biological and chemical sensors and instruments
for materials design and characterization.

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