Controllable Liquid Crystal Microdroplets via Thermal Diffusion-Induced Phase Separation

Abstract

Micrometer-sized droplets composed of liquid crystals (LCs) report unique electro-optical signals. Polymer dispersed LC droplets are representative system, offering versatile functionality under various external stimuli, but controlling droplet size and number density remains as a challenge. In this work, we present a versatile design rule for manipulating size and number density of LC microdroplets through thermal diffusion-induced phase separation. Specifically, to produce LC microdroplets, we employed poly (octadecyl methacrylate) (PODMA) for the encapsulation of LCs. As temperature increased, the LCs diffused into a PODMA layer. Subsequently, a decrease in temperature resulted in the patterned phase separation into birefringent hemisphere droplets attached to the substrate. Droplet size and density are precisely controlled by polymer side chain length, heating temperature, and rate of temperature change. This microdroplet array allows us to design various surface functionalities such as wettability, besides optical signals. This work was supported by the NRF (2021R1A4A1030944, 2021R1A2C2095010 and 2022M3C1A3081312).