Orientational dynamics of a heated Janus particle

Area of Science:

• Soft Matter Physics
• Computational Physics
• Colloid Science

Background:

• Janus particles are colloids with two distinct hemispheres, enabling anisotropic interactions.
• Self-propulsion in Janus particles arises from gradients, often temperature, generated by their asymmetric properties.
• Understanding orientational and translational dynamics is crucial for controlling micro-swimmer behavior.

Purpose of the Study:

• To investigate the orientational dynamics of a heated Janus particle exhibiting self-propulsion.
• To analyze the enhancement of translational diffusivity at late times due to self-propulsion.
• To correlate rotational diffusion with temperature gradients and microscopic interactions.

Main Methods:

• Large-scale molecular dynamics simulations were employed.
• Asymmetric wetting parameters created a temperature gradient across the Janus particle.
• Orientational correlation functions and propulsion velocity were measured.

Main Results:

• A self-created temperature gradient drives self-propulsion along the symmetry axis.
• Heating increases rotational diffusivity, which is better correlated with average surface temperature difference (ΔT) than polar temperature difference (δT).
• Propulsion velocity depends on wetting parameters, changing sign when attractive interactions are removed, and is zero below a temperature threshold.

Conclusions:

• The study quantifies the relationship between temperature gradients and the dynamics of self-propelled Janus particles.
• Rotational diffusion and translational diffusivity are enhanced by self-propulsion.
• The findings provide insights into controlling micro-swimmer behavior through engineered temperature gradients.