Berlin 2012 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 16: Poster: Colloids and Complex Liquids
CPP 16.17: Poster
Tuesday, March 27, 2012, 18:15–20:45, Poster A
Friction within single pairs of DNA grafted colloids as studied by optical tweezers — •Mahdy M. Elmahdy1,2, Olaf Ueberschär1, Carolin Wagner1, Tim Stangner1, Christof Gutsche1, and Friedrich Kremer1 — 1Institute of Experimental Physics I, Leipzig University, Linnéstrasse 5, 04103, Leipzig, Germany — 2Department of Physics, Mansoura University, Mansoura 35516, Egypt
Optical Tweezers are employed to study the transition from sliding to stick-slip friction between two DNA grafted (grafting density ~1000 molecules per particle, number of base pairs per grafted chain ~4000) colloids. The latter are moved with a relative velocity in respect to each other ranging between 50 nm/s up to 3 μm/s; one colloid is fixed to a micropipette while the other is held in the optical trap hence enabling one to determine and to separate the forces of interaction in the direction parallel and perpendicular to the motion. Further parameter to be varied is the salt (NaCl) concentration of the surrounding medium at pH 8.5. A transition from sliding to stick-slip friction is found and shown to be controlled by the product of interaction volume and interaction time.