Liquid Crystal Janus Droplets

Janus colloids are composed of two-faced particles with distinctive surfaces and/or compartments. Lee, Collings, & Yodh have created the first Janus particles with a liquid crystal (LC) compartment. The droplets were prepared by combining microfluidic and phase separation techniques, and the LC compartment morphologies can be easily controlled to realize unique confining geometries (Fig. 1).

The group demonstrated the anisotropic optical character of the droplets and showed how other differences, in density and solubility, can lead to  interesting dynamic behaviors such as the gravity-induced tumbling and directional self-propelled swimming motions (Fig. 2). Finally, the coalescence of multiple Janus droplets creates potential to make patchy particles with more complex ternary and tetragonal structure that could be used to assemble  complex colloidal materials (Fig. 3).

These LC Janus colloids take first steps toward new kinds of applications in self-assembly, photonics, and active soft matter.

Fig. 1 (left) Schematic of a Janus droplet with two phase-separated compartments: polymer (top) and LC (bottom). (others) Bright-field images of LC Janus droplets with different polymer:LC volume ratios and background surfactant.

Fig. 2 (left) Side- and bottom-view polarized optical microscopy images of a Janus droplet. (middle) Floating aligned Janus droplets near an air–water interface. (left) Self-propelled motion of Janus droplets and LC droplets.

Fig. 3 Droplets with 2, 3, & 4 polymer compartments connected by a LC compartment, respectively.

J. Jeong et al. (Soft Matter, 2015)