force modulation

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Stephen Minne replied on Mon, Jan 17 2011 5:55 PM

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Investigation of True Surface Morphology and Nanomechanical Properties of Poly(styrene-b-ethylene-co-butylene-b-styrene) Using Nanomechanical Mapping: Effects of Composition

Dong Wang,* So Fujinami, Hao Liu, Ken Nakajima, and Toshio Nishi

WPI Advanced Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba,
Sendai 980-8577, Japan

Received April 30, 2010; Revised Manuscript Received August 29, 2010

ABSTRACT: The surface morphology and nanomechanical properties of poly(styrene-b-ethylene-cobutylene-b-styrene) (SEBS) having different compositions were investigated using nanomechanical mapping measurements based on atomic force microscopy. We obtained the deformation image, true surface morphology, high-resolution Young’s modulus map, and map of deviated work simultaneously in a force mapping. Such maps were successfully used to identify and characterize the composition and better understand the relationship between microstructure and properties of SEBS samples. It is found that theobtained Young’s modulus and deformation values, both for polystyrene (PS) or poly(ethylene-co-butylene)(PEB) blocks, strongly depend on the microstructure that is dominated by the composition. As the PS composition increase, the modulus of PS blocks increases from 19.2 ( 2.5 MPa for SEBS (10/80/10) to 823.0(168.1 MPa for SEBS (33.5/33/33.5), while PEB’s increases from 8.7(2.1 MPa for SEBS (10/80/10) to 97.6( 17.8 MPa for SEBS (33.5/33/33.5). The calculated map of deviated work from elastic model will be a convenient technique to visualize the distribution of viscoelasticity. Furthermore, the reconstructed true height image reveals the true topographic feature free from sample deformation.

And

Effect of streptolysin O on the microelasticity of human platelets analyzed by atomic force microscopy

M. Walch1, U. Ziegler,*,1 P. Groscurth

Institute of Anatomy, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland

Received 31 May 1999; received in revised form 26 August 1999

Abstract
Atomic force microscopy (AFM) has been shown to be a suitable tool to probe biophysical properties of cells and cell fragments. We analysed biophysical alterations of human platelets by AFM using streptolysin O (SLO) as a model for pore forming proteins. Permeabilization of platelet membrane by SLO was con"rmed by transmission electron and confocal microscopy. Using force volume imaging combined with FIEL analysis we were able to show dynamically the increase in the elasticity of platelets during the pore formation by SLO and could correlate the viscoelasticity to the morphology of platelets. Stabilizing the actin cytoskeleton by phalloidin resulted in partial restoration of the elasticity indicating that loss of stability in platelets by SLO is mediated by alterations of both plasma membrane and cytoskeleton.