Regensburg 2007 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
CPP: Fachverband Chemische Physik und Polymerphysik
CPP 24: Micro and Nano Fluidics II: Soft Objects in Flow + Slippage
CPP 24.7: Vortrag
Donnerstag, 29. März 2007, 11:30–11:45, H37
Microrheology on (DNA-grafted) colloids using Optical tweezers — •Christof Gutsche1, Ulrich Keyser1, Kati Kegler1, Mathias Salomo2, and Friedrich Kremer1 — 1Univ Leipzig, Inst Expt Phys 1, Leipzig, Germany — 2Univ Leipzig, Inst Biochem, Leipzig, Germany
Optical Tweezers are employed to measure the forces of interaction within single pairs of (DNA-grafted) colloids in media of monovalent and divalent ionic aqueous solutions of varying concentrations. For monovalent ions the data for the blank colloids are well described by the DLVO theory but as well by a novel Poisson-Boltzmann approach. Additional parameters to be varied for grafted colloids are the length of the DNA and the grafting density. From the measured force-separation dependence an interaction length at a given force is deduced. It shows in the "mushroom" regime a scaling with the grafting density which levels off for brushes [1]. The flow resistance of single blank or DNA-grafted colloids is determined and compared. The degree of swelling of the grafted DNA is adjusted by exchanging the ion concentration of the surrounding medium. For all examined flow velocities one observes an interesting deviation from Stokes law which can be traced back to a shear-dependent conformational change of the brush layer [2].
[1] K. Kegler, M. Salomo, and F. Kremer, in Press Phys. Rev. Lett.(2006) [2] C. Gutsche, M. Salomo, Y.W. Kim, R.R. Netz and F. Kremer, MICROFLUIDICS AND NANOFLUIDICS 2 (5): 381-386 SEP (2006)