[BNC-grads-list] FW: First PU-SPM group meeting spring 2009 semester, Friday January 16 Birck 1001

[Deborah S. Starewich]

------ Forwarded Message
From: <rbwagner at purdue.edu>
Date: Mon, 12 Jan 2009 19:20:27 -0500
To: 
Subject: First PU-SPM group meeting spring 2009 semester, Friday January 16
Birck 1001


Dear PU-SPM community,

My name is Ryan Wagner and I am the student coordinator for the Purdue
University Scanning Probe Microscopy (PU-SPM) group.  The PU-SPM group holds
biweekly meetings where a graduate student, post doc, or visiting professor
gives a talk about SPM related research.   It is an opportunity to learn
about 
the diverse field of SPM from the perspective of SPM users from different
backgrounds.  

The first meeting of this semester will be held on Friday, January 16th in
Brick 1001.  Free pizza will be provided!!!! The pizza will arrive at 11:30
and 
the talk will begin at noon.

Our first speaker is Ms. Xin Xu, a Doctoral Candidate in the School of
Mechanical Engineering who works out of the Brick Nanotechnology Center.
The 
title and abstract for her talk can be found below.

I hope to see you there,
Ryan Wagner 
Graduate Student, Mechanical Engineering
Office, Birck 1080

P.S.  The PU-SPM group also has a forum on the Birck Nanotechnology website
(www.purdue.edu/nano) under the BNC users forum link where users can post
any 
questions about the meetings or SPM work in general.


Talk Information

Title: 

Dynamic atomic force microscopy of soft biological samples in
liquids: a summary of some recent results

Abstract:

Dynamic atomic force microscopy (dAFM) or tapping mode under liquids is
becoming increasingly important for the nanoscale imaging and force
spectroscopy of fragile biological samples  in their quasi-native state.

Most AFM systems now support a "Force-volume" capability that can
simultaneously map local topography and forces over soft sample in
liquids. While the interpretation of data is relatively easy with the
"force-volume" mode, this mode is much slower, less sensitive, and
usually applies greater imaging forces compared to dAFM (tapping mode).
Large imaging force can easily crush fragile biological samples.

On the other hand, tapping mode AFM can provide simultaneous
compositional contrast (such as local elasticity maps) and topography
images at fast speeds and with gentler imaging forces, but its data
interpretation is more complex due to the differences in cantilever
excitation used in liquids and the nonlinear dynamics of the oscillating
probe interacting with the sample. Moreover it is hard to "know"
precisely the force applied by the oscillating probe as it taps on a
soft sample, and to understand quantitatively how to chose cantilevers
and operating conditions to minimize imaging forces.

In this talk I will summarize the results of my thesis research
related to quantitative aspects of dAFM under liquid environments.
Specifically I will (a) highlight our recent results that show the
fundamental differences between acoustic (dither piezo), magnetic and
Brownian motion driven vibration response of AFM cantilevers in liquids,
(b) present a theoretical result and its experimental validation that
allows for a simple formula to guide the selection of cantilevers and
operating conditions to minimize imaging forces, (c) present a new way
to measure and enhance local elasticity maps by two orders of magnitude
while operating in the tapping mode, and (d) show how laser positioning
can be used to avoid artifacts in force spectroscopy that occurs due to
unusual cantilever dynamics in liquids.



If you would no longer like to receive this email or know of anyone who
would 
like to be added to this email list please send a message to
rbwagner at purdue.edu.


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