Viscosity measurement using a rotating laser-trapped microsphere of liquid crystalN. Murazawa, S. Juodkazis, V. Jarutis, Y. Tanamura and H. Misawa
CREST-JST and Research Institute for Electronic Science, Hokkaido University N21-W10, CRIS Bldg., Kita-ku, Sapporo 001-0021, Japan
received 1 November 2005; accepted in final form 10 January 2006
published online 27 January 2006
We demonstrate that the viscosity measurement by a spinning laser-trapped liquid-crystal microsphere depends on the surface tension and hydrophobicity of sphere's material. A reduction of the viscous drag was observed for the hydrophobic E44 liquid-crystal droplets even at low surface tension, while a reduced surface tension caused an increased drag in the case of 5CB microspheres. The importance of the non-slipping boundary condition and light propagation throughout the laser-trapped microsphere in the viscosity measurements by a spinning microsphere (BISHOP A. I. et al. , Phys. Rev. Lett., 92 (2004) 198104) is discussed.
83.85.Jn - Viscosity measurements.
83.85.Ei - Optical methods; rheo-optics.
42.70.Df - Optical materials: Liquid crystals.
© EDP Sciences 2006