Hydrodynamic effects in the measurement of interparticle forces in nematic colloids.

We propose improved measurement methods of interparticle force between nematic colloids. Although various methods have been utilized for the force measurement, the comparison between the forces obtained by different methods has not been reported. In the frequently used method called the "free-release" method, the hydrodynamic interaction between moving particles has a serious influence on the measurement. In this study we modified those measurement methods by taking the long-ranged hydrodynamic interaction into account. The evaluated forces have been compared with that obtained by the dual beam "optical trap" method, which is free from the hydrodynamic effect. The agreement between them is quantitatively fairly good.