Liquid Crystal Structure of Supercooled Liquid Gallium and Eutectic Gallium–Indium

Abstract

Understanding the origin of structural ordering in supercooled liquid gallium (Ga) has been a great scientific quest in the past decades. Here, reflective polarized optical microscopy on Ga sandwiched between glasses treated with rubbed polymers reveals the onset of an anisotropic reflection at 120 °C that increases on cooling and persists down to room temperature or below. The polymer rubbing usually aligns the director of thermotropic liquid crystals (LCs) parallel to the rubbing direction. On the other hand, when Ga is sandwiched between substrates that align conventional LC molecules normal to the surface, the reflection is isotropic, but mechanical shear force induces anisotropic reflection that relaxes in seconds. Such alignment effects and shear‐induced realignment are typical to conventional thermotropic LCs and indicate a LC structure of liquid Ga. Specifically, Ga textures obtained by atomic force and scanning electron microscopy reveal the existence of a lamellar structure corresponding to a smectic LC phase, while the nanometer‐thin lamellar structure is transparent under transmission polarized optical microscopy. Such spatial molecular arrangements may be attributed to dimer molecular entities in the supercooled liquid Ga. The LC structure observation of electrically conductive liquid Ga can provide new opportunities in materials science and LC applications.

Liquid Metal Actuators: A Comparative Analysis of Surface Tension Controlled Actuation

“…We emphasize surface tension as the primary driving mechanism. As a counterexample, liquid crystal elastomers with embedded liquid metal droplets [68][69][70][71] operate on liquid crystal phase transitions and therefore do not qualify as liquid metal actuators. Neither are material architectures with non-actuating liquid metal inclusions, such as has been demonstrated with dielectric elastomers, [72,73] McKibben pneumatic actuators, [74] and shape memory alloys.…”

Size Dependent Phase Transformation of Liquid Gallium

“…[ 45 ] Yunusa et al. [ 46 ] performed advanced experimental study on the structural ordering of supercooled liquid Ga. They revealed a possible liquid crystal mesophase by sandwiching Ga between polymer‐coated glass substrates.…”