Colloidal particles at a nematic-isotropic interface: Effects of confinement

Abstract.When captured by a flat nematic-isotropic interface, colloidal particles can be dragged by it. As a result spatially periodic structures may appear, with the period depending on particle mass, size, and interface velocity (J.L. West, A. Glushchenko, G.X. Liao, Y. Reznikov, D. Andrienko, M.P. Allen, Phys. Rev. E 66, 012702 (2002)). If liquid crystal is sandwiched between two substrates, the interface takes a wedge-like shape, accommodating the interface-substrate contact angle and minimizing the director distortions on its nematic side. Correspondingly, particles move along complex trajectories: they are first captured by the interface and then “glide” towards its vertex point. Our experiments quantify this scenario, and numerical minimization of the Landau-de Gennes free energy allows for a qualitative description of the interfacial structure and the drag force.

[1]  Effective pair interactions between colloidal particles at a nematic-isotropic interface , 2005, cond-mat/0501573.

[2]  H. Stark,et al.  Twist transition in nematic droplets: a stability analysis , 1999 .

[3]  K. Yoshinaga,et al.  Formation of colloid crystals from polymer-modified monodisperse colloidal silica in organic solvents , 1999 .

[4]  R. Pethig,et al.  Dielectrophoretic separation of bacteria using a conductivity gradient. , 1996, Journal of biotechnology.

[5]  H. A. Pohl.  The Motion and Precipitation of Suspensoids in Divergent Electric Fields , 1951 .

[6]  Lavrentovich.  Geometrical anchoring at an inclined surface of a liquid crystal. , 1992, Physical review. A, Atomic, molecular, and optical physics.

[7]  V. Palleschi,et al.  Nematic-isotropic interface of some members of the homologous series of 4-cyano-4'-(n-alkyl)biphenyl liquid crystals , 1984 .

[8]  O. Velev,et al.  Formation of two-dimensional colloid crystals in liquid films under the action of capillary forces , 1994 .

[9]  O. Lavrentovich,et al.  Effect of director distortions on morphologies of phase separation in liquid crystals. , 2002, Physical review. E, Statistical, nonlinear, and soft matter physics.

[10]  Interaction of colloids with a nematic-isotropic interface. , 2003, Physical review. E, Statistical, nonlinear, and soft matter physics.

[11]  H. Yokoyama,et al.  Depression of the nematic-isotropic phase transition temperature at nanopatterned surfaces. , 2002, Physical review. E, Statistical, nonlinear, and soft matter physics.

[12]  H Morgan,et al.  Separation of submicron bioparticles by dielectrophoresis. , 1999, Biophysical journal.

[13]  P. Patrício,et al.  Colloidal dipolar interactions in 2D smectic-C films , 2002 .

[14]  Oswald,et al.  Destabilization of a flat nematic-isotropic interface. , 1989, Physical review. A, General physics.

[15]  J. Straley,et al.  Physics of liquid crystals , 1974 .

[16]  Colloidal interactions in two-dimensional nematics , 2002, The European physical journal. E, Soft matter.

[17]  Harry J. Coles,et al.  Laser and Electric Field Induced Birefringence Studies on the Cyanobiphenyl Homologues , 1978 .

[18]  Colloidal discs in nematic liquid crystals , 2004 .

[19]  Zumer,et al.  Nematic-isotropic phase transition in a liquid-crystal droplet. , 1991, Physical review. A, Atomic, molecular, and optical physics.

[20]  Vladimir G. Chigrinov,et al.  Electro‐Optic Effects in Liquid Crystal Materials , 1995 .

[21]  Instabilities of a moving nematic-isotropic interface. , 1987, Physical review letters.

[22]  Denis Andrienko,et al.  Drag on particles in a nematic suspension by a moving nematic-isotropic interface. , 2002, Physical review. E, Statistical, nonlinear, and soft matter physics.

[23]  M. Washizu,et al.  Electrostatic manipulation of DNA in microfabricated structures , 1989, Conference Record of the IEEE Industry Applications Society Annual Meeting,.

[24]  David A. Weitz,et al.  INVERTED AND MULTIPLE NEMATIC EMULSIONS , 1998 .

[25]  Denis Andrienko,et al.  Mechanism of Formation of Three Dimensional Structures of Particles in a Liquid Crystal , 2002 .

[26]  Director field configurations around a spherical particle in a nematic liquid crystal , 1998, cond-mat/9811229.

[27]  Masao Washizu.  Electrostatic manipulation of biological objects , 1990 .

[28]  P. Gennes,et al.  The physics of liquid crystals , 1974 .