Flow pattern in the vicinity of self-propelling hot Janus particles

Area of Science:

• Physics
• Fluid Dynamics
• Materials Science

Background:

• Janus particles are microscale objects with distinct surface properties.
• Understanding their thermal and flow behavior is crucial for microfluidics and material science.
• Previous studies have explored Janus particle locomotion but less on their thermal-induced flow patterns.

Purpose of the Study:

• To investigate the temperature field and fluid flow generated by a heated metal-capped Janus particle.
• To determine how the metal cap's thickness influences the flow dynamics.
• To explore potential applications in understanding collective behaviors and tracer motion.

Main Methods:

• Theoretical modeling of the temperature field around a Janus particle.
• Analysis of the resulting fluid flow patterns using hydrodynamic theory.
• Comparison of flow behavior for different metal cap thicknesses (above and below 10 nm).

Main Results:

• A metal cap thickness exceeding approximately 10 nm results in an isothermal cap.
• For thicker caps, the flow pattern is characterized by a quadrupolar term decaying as ~r(-2).
• For significantly thinner caps, the fluid velocity exhibits a decay rate of ~r(-3).

Conclusions:

• The thickness of the metal cap on a Janus particle critically dictates the near-field flow pattern.
• These findings are relevant for understanding collective effects in dense Janus particle suspensions.
• The study provides insights into the circular tracer motion observed around tethered Janus particles.