Rodeo in liquid crystal (Vol. 46 No. 3)

Rodeo in liquid crystal
Binding of a dipolar microsphere with a point monopole on a fiber

Scientists have achieved an unprecedented level of control over defects in liquid crystals that can be engineered for applications in liquid matter photonics.

Sitting with a joystick in the comfort of their chairs, scientists can play “rodeo” on a screen magnifying what is happening under their microscope. They use very strong laser tweezers to locally melt the liquid crystal into a phase where the molecules are oriented in all directions, encircling one part of the fibre. They subsequently switch-off the laser light, resulting in molecules reverting back from being oriented in all directions to being parallel to each other, creating several pairs of defects—akin to localised disruptions of the crystal’s ordering field —forming a ring. The defect ring is used as a non-material "rope" to entangle and strongly bind a microsphere and long fibre of micrometric diameter. The results of this work have been published recently by the authors. They believe that their findings could ultimately open the door to controlling the flow of light using light of a specific frequency in the Gigahertz range in liquid crystal photonic microdevices.

M. Nikkhou, M. Škarabot and I. Muševič,, Topological binding and elastic interactions of microspheres and fibres in a nematic liquid crystal, Eur. Phys. J. E, 38, 23 (2015)