Active Janus Particles at Interfaces of Liquid Crystals

Area of Science:

• Soft Matter Physics
• Colloid Science
• Interfacial Phenomena

Background:

• Janus particles (JPs) are engineered colloids with distinct surface properties.
• Active motion of JPs is typically studied at isotropic liquid interfaces.
• Nematic liquid crystals (LCs) possess unique elastic and anisotropic viscous properties.

Purpose of the Study:

• To investigate the active motion of silica-palladium JPs at nematic LC-aqueous interfaces.
• To understand how LC properties influence JP motion compared to isotropic interfaces.
• To explore the role of hydrogen peroxide (H2O2) concentration on JP propulsion dynamics.

Main Methods:

• Adsorption of silica-palladium JPs at nematic LC-aqueous interfaces.
• Observation and analysis of JP active motion under varying H2O2 concentrations.
• Measurement of JP orientations and calculation of elastic energies.

Main Results:

• LC elasticity and viscosity qualitatively alter JP active motion.
• Contact line pinning restricts out-of-plane rotation; LC anchoring biases in-plane motion along the director at low H2O2.
• At higher H2O2 concentrations, JPs exhibit motion parallel and perpendicular to the director, with a subpopulation moving exclusively perpendicular.

Conclusions:

• Nematic LC interfaces significantly modify JP self-propulsion mechanisms.
• JP motion is dictated by a combination of interfacial anchoring, LC director orientation, and H2O2-driven propulsion.
• These findings offer insights into controlling active matter at complex fluid interfaces.