------ Forwarded Message From: <rbwagner@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@purdue.edu. ------ End of Forwarded Message