Dear PUSPM community,

I hope everyone's summer went well.  The Purdue University Scanning Probe
Microscopy (PUSPM) user's group seminar series will be continued during the Fall
2009 semester. The first talk of the semester will be this Friday, August 28th
in Birck 2001.  

Daniel Kiracofe, a PHD student in Professor Raman's research group will be
giving a talk titled "On eigenmodes, stiffness, and sensitivity of atomic force
microscope cantilevers in air versus liquids."  Please see the below abstract
for more information.  Pizza will be provided at 11:30 a.m., the talk will begin
at noon, and end by 1:00 p.m..  

Please see the attached files.  Or visit our website
(www.engineering.purdue.edu/PUSPM) for more information about the upcoming
semester.


I hope to see you there,
Ryan Wagner
PUSPM student coordinator


P.S. To be removed from this email list send the request to rbwagner@purdue.edu.


Abstract:
The effect of hydrodynamic loading on the eigenmode shapes, modal stiffnesses,
and optical lever sensitivities of Atomic Force Microscope (AFM)
microcantilevers is investigated by measuring the vibrations of such
microcantilevers in air and water using a scanning laser Doppler vibrometer. It
is found that for rectangular tipless microcantilevers, the measured fundamental
and higher eigenmodes and their equivalent stiffnesses are nearly identical in
air and in water. However, for microcantilevers with a tip mass or for picket
shaped cantilevers there is a marked difference in the second (and higher)
eigenmode shapes between air and water that leads to a large decrease of modal
stiffness in water as compared to air, as well as a decrease in optical lever
sensitivity. These results are explained in terms of hydrodynamic interactions
of microcantilevers with non-uniform mass distribution. The results clearly
demonstrate that tip mass and hydrodynamic loading must be taken into account in
calibration while using higher-order eigenmodes in dynamic AFM.