Director-configurational transitions around microbubbles of hydrostatically regulated size in liquid crystals.

A high-pressure technique is introduced which allows a continuous variation of the inclusion size in liquid crystal colloids. We use a nematic liquid crystal host into which micrometer-sized gas bubbles are injected. By applying hydrostatic pressures, the diameter of these gas bubbles can be continuously decreased via compression and absorption of gas into the host liquid crystal, so that the director configurations around a single bubble can be investigated as a function of the bubble size. The theoretically predicted transition from a hyperbolic hedgehog to a Saturn-ring configuration, on reduction of the particle size below a certain threshold, is confirmed to occur at the radius of a few micrometers.