CiteULike: dchens opticaltweezer http://www.citeulike.org/user/dchen/tag/opticaltweezer CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/dchen/article/2801926 <i>Fungal Genetics and Biology, Vol. 44, No. 1. (January 2007), pp. 1-13.</i><br /><br />Optical tweezers have been little used in experimental studies on filamentous fungi. We have built a simple, compact, easy-to-use, safe and robust optical tweezer system that can be used with brightfield, phase contrast, differential interference contrast and fluorescence optics on a standard research grade light microscope. We have used this optical tweezer system in a range of cell biology applications to trap and micromanipulate whole fungal cells, organelles within cells, and beads. We have demonstrated how optical tweezers can be used to: unambiguously determine whether hyphae are actively homing towards each other; move the Spitzenkörper and change the pattern of hyphal morphogenesis; make piconewton force measurements; mechanically stimulate hyphal tips; and deliver chemicals to localized regions of hyphae. Significant novel experimental findings from our study were that germ tubes generated significantly smaller growth forces than leading hyphae, and that both hyphal types exhibited growth responses to mechanical stimulation with optically trapped polystyrene beads. Germinated spores that had been optically trapped for 25 min exhibited no deleterious effects with regard to conidial anastomosis tube growth, homing or fusion. Optical tweezer micromanipulation of filamentous fungi Graham Wright Jochen Arlt Wilson Poon Nick Read doi:10.1016/j.fgb.2006.07.002 Fungal Genetics and Biology, Vol. 44, No. 1. (January 2007), pp. 1-13. 2008-05-15T14:58:07-00:00 Fungal Genetics and Biology 44 1 1 13 2006 biology opticaltweezer poon tracer http://www.citeulike.org/user/dchen/article/2767397 <i>Physical Review Letters, Vol. 100, No. 11. (2008)</i><br /><br />Optical tweezers are employed to measure the forces of interaction within a single pair of DNA-grafted colloids, dependent on the molecular weight of the DNA chains, and the concentration and valence of the surrounding ionic medium. The resulting forces are short range and set in as the surface-to-surface distance between the colloidal cores reaches the value of the brush height. The measured force-distance relation is analyzed by means of a theoretical treatment that quantitatively describes the effects of compression of the chains on the surface of the opposite-lying colloid. Quantitative agreement with the experiment is obtained for all parameter combinations. Polyelectrolyte-Compression Forces between Spherical DNA Brushes Kati Kegler Martin Konieczny Gustavo Espinosa Christof Gutsche Matthias Salomo Friedrich Kremer Christos Likos doi:10.1103/PhysRevLett.100.118302 Physical Review Letters, Vol. 100, No. 11. (2008) 2008-05-07T21:14:58-00:00 Physical Review Letters 100 11 APS biology colloids interaction opticaltweezer http://www.citeulike.org/user/dchen/article/963666 <i>Physical Review Letters, Vol. 97, No. 21. (2006)</i><br /><br />We report the statistical analysis of the movement of a submicron particle confined in a harmonic potential in the presence of a torque. The absolute value of the torque can be found from the auto- and cross-correlation functions of the particle's coordinates. We experimentally prove this analysis by detecting the torque produced onto an optically trapped particle by an optical beam with orbital angular momentum. Torque Detection using Brownian Fluctuations Giovanni Volpe Dmitri Petrov doi:10.1103/PhysRevLett.97.210603 Physical Review Letters, Vol. 97, No. 21. (2006) 2006-11-27T18:32:15-00:00 Physical Review Letters 97 21 APS 2006 focus opticaltweezer rotation http://www.citeulike.org/user/dchen/article/2747059 <i>Review of Scientific Instruments, Vol. 69, No. 5. (1998), pp. 1974-1977.</i> Optical tweezer arrays and optical substrates created with diffractive optics Eric Dufresne David Grier Review of Scientific Instruments, Vol. 69, No. 5. (1998), pp. 1974-1977. 2008-05-02T20:52:54-00:00 Review of Scientific Instruments 69 5 1974 1977 AIP grier opticaltweezer http://www.citeulike.org/user/dchen/article/2735618 <i>Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol. 359, No. 1782. (15 May 2001), pp. 921-937.</i><br /><br />In this paper we present fundamental studies elucidating the role of entropy in particle suspensions. We focus on systems composed of large colloidal particles along with a second, usually smaller species such as a particle or polymer. We describe direct measurements of these interactions in suspension, and we systematically show how these forces can be used to control the self-assembly of colloidal particles. The paper provides a unified review of the experiments from our laboratory, and in a few cases touches on very recent results. Entropically driven self-assembly and interaction in suspension Yodh doi:10.1098/rsta.2000.0810 Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol. 359, No. 1782. (15 May 2001), pp. 921-937. 2008-04-29T23:03:20-00:00 Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 359 1782 921 937 colloids opticaltweezer yodh http://www.citeulike.org/user/dchen/article/2730851 <i>Journal of Rheology, Vol. 50, No. 1. (2006), pp. 77-92.</i><br /><br />The microrheology of a colloidal suspension is measured using laser tweezers. Suspensions of refractive index-matched fluorinated ethylene propylene (FEP) particles are seeded with index-mismatched polystyrene or silica probe particles. Laser trapped probes are then subjected to steady uniform flows, enabling measurements of the suspension microviscosity as a function of FEP volume fraction and flow velocity. The microrheology results agree with bulk rheology, and both exhibit the same volume fraction dependence of the Krieger-Dougherty relationship for hard spheres. As volume fraction increases, the microrheology more closely agrees with the infinite shear bulk viscosity. In this regime, measurements using small probes exhibit additional shear thinning. Using confocal microscopy and fluorescent poly(methylmethacrylate) dispersions, we demonstrate that the nonlinear microrheology is consistent with the development of an anisotropic nonequilibrium pair distribution function between the probe and bath particles, with a denser region at the leading surface of the probe and a wake trailing it. The nonlinear response and underlying microstructure are in qualitative agreement with recent theory [T. M. Squires and J. F. Brady, Phys. Fluids 17, 073101 (2005)]. ©2006 The Society of Rheology Laser tweezer microrheology of a colloidal suspension Alexander Meyer Andrew Marshall Brian Bush Eric Furst doi:10.1122/1.2139098 Journal of Rheology, Vol. 50, No. 1. (2006), pp. 77-92. 2008-04-28T19:22:56-00:00 Journal of Rheology 50 1 77 92 SOR colloids microrheology opticaltweezer technique http://www.citeulike.org/user/dchen/article/2683399 <i>Applied Physics Letters, Vol. 91, No. 9. (2007)</i><br /><br />View this record in Web of Science Optical manipulation and rotation of liquid crystal drops using high-index fiber-optic tweezers Kazi Abedin Charles Kerbage Alberto Nieves David Weitz Applied Physics Letters, Vol. 91, No. 9. (2007) 2008-04-17T20:15:01-00:00 Applied Physics Letters 91 9 AIP 2007 liquidcrystal opticaltweezer weitz http://www.citeulike.org/user/dchen/article/2563086 <i>Physical Review Letters, Vol. 98, No. 5. (2007)</i><br /><br />Optical tweezers are employed to measure the forces of interaction between single DNA-grafted colloids. Parameters to be varied are the length of the DNA, the grafting density, and the ion concentration of the surrounding medium. 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. For the latter the transition from an osmotic to a salted brush can be traced in detail by varying the ion concentration in accordance with mean field theories. Forces of Interaction between DNA-Grafted Colloids: An Optical Tweezer Measurement K Kegler M Salomo F Kremer doi:10.1103/PhysRevLett.98.058304 Physical Review Letters, Vol. 98, No. 5. (2007) 2008-03-19T16:59:43-00:00 Physical Review Letters 98 5 APS 2007 biology colloids opticaltweezer