Autophoretic motion in three dimensions.

Area of Science:

• Active Matter Physics
• Soft Matter Science
• Theoretical Nanotechnology

Background:

• Janus particles are model systems for active matter, exhibiting phoretic motion in self-generated chemical gradients.
• Their typical motion involves straight paths with rotational diffusion as the primary reorientation mechanism.

Purpose of the Study:

• To theoretically investigate the induction of arbitrary three-dimensional translational and rotational motion in Janus particles.
• To demonstrate control over helical trajectory parameters like pitch and radius through surface property manipulation.

Main Methods:

• Development of a theoretical framework based on classical axisymmetric self-phoretic motion.
• Calculation of general three-dimensional motion for arbitrary spherical particle surface coverage.
• Introduction of a simplified patch model for practical design guidance.

Main Results:

• Demonstration that tailored surface coverage of activity and mobility induces arbitrary 3D motion.
• Prediction of helical trajectories where pitch and radius are controllable via velocity vector alignment.
• Validation of theoretical predictions with illustrative surface distribution examples.

Conclusions:

• Arbitrary 3D motion and controlled helical trajectories are achievable in Janus particles.
• Surface engineering offers a powerful method to dictate the complex motion of active particles.
• The patch model provides a design roadmap for creating bespoke phoretic spheres.