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An AFM Study of the Deformation and Nanorheology of Cross-Linked PDMS Droplets

Summary: An AFM Study of the Deformation and Nanorheology of
Cross-Linked PDMS Droplets
Graeme Gillies, Clive A. Prestidge, and Phil Attard*
Ian Wark Research Institute, University of South Australia,
Mawson Lakes, South Australia 5095, Australia
Received September 21, 2001. In Final Form: November 16, 2001
Interaction forces between a spherical silica probe and a cross-linked poly(dimethylsiloxane) (PDMS)
colloidal droplet have been determined by atomic force microscopy (AFM). On approach of the surfaces,
as a result of deformation of the PDMS, the repulsive force increases much less rapidly than expected for
electrical double layer interaction of rigid particles. The amount of deformation is dependent on the loading
force and the drive velocity and reflects the nanorheological response of the PDMS. On retraction of the
surfaces, force curve hysteresis is observed and is dependent on the rate of approach/retraction. Hysteresis
is due to the viscoelastic response of the PDMS droplet and can be described by theory (Attard, P. Phys.
Rev. E 2001, 63, 061604). The moduli and the characteristic relaxation time of the PDMS colloid have been
determined from the force measurements and offer a novel description of the nanorheological properties.
Interaction forces between colloidal particles have been
(AFM) in colloid probe mode.1-14


Source: Attard, Phil - School of Chemistry, University of Sydney


Collections: Chemistry