Dr. Igor Sokolov of Tufts University

Professor Igor Sokolov of Tufts University will present

"Novel Multidimensional Imaging of Surfaces with Atomic Force Microscopy"

on February 6, 2019 at 4:10pm in Neville Hall, Room 3

Atomic force microscopy (AFM) is a unique tool to visualize physical and chemical properties of materials down to the nanoscale. It opens new dimensions in quantitative study and development of polymers, nanocomposites and biomaterials. AFM allows simultaneous collecting of multidimensional information of a sample surface. Here I overview recent developments of my lab in this direction.

The 1st development is the fast Fourier-transfer nano-dynamical mechanical analysis/ spectroscopy (FT-NanoDMA). This nanoindentation mode allows to measure storage and loss moduli of soft materials at the range of biologically interesting small frequencies (up to 500Hz; the same range is used to describe polymers in industry). FT-NanoDMA is a combination of three different methods: the quantitative dynamic mechanical spectroscopy (DMS), AFM indentation, and Fourier-transform spectroscopy. This mode is fast and sensitive enough to allow DMS imaging of nanointerfaces and single biological cells. Compared to the existing state-of-the-art nanoindentation, FT-NanoDMA demonstrates ~ 100x improvements in both spatial (down to 10nm) and temporal resolution (down to 0.7 sec/pixel). I will show the work of this technique on known biomaterials, biological cells and polymers blends.

The 2nd development is in the area of sub-resonant tapping, so-called Ringing mode. Compared to the existing sub-resonant tapping (such as Digital Pulse, PeakForce Tapping, HybriD, etc.), this mode allows obtaining to up to 8 new additional channels of information, such as adhesion height, adhesion neck height, detachment energy losses, size of possibly stretchable molecules, etc. In addition, Ringing mode can be up to 20 times faster and showing fewer artifacts compared to the rival existing sub-resonance tapping modes. I will demonstrate the work of this new mode on complex samples, such as fixed human epithelial cells, corneocyte skin flakes, and polymeric nanocomposites. Examples of potential medical applications of the presented modes will be overviewed.