Direct-imaging of light-driven colloidal Janus particles in weightlessness.

Area of Science:

• Physics
• Materials Science
• Nanotechnology

Background:

• Active Brownian motion is crucial for understanding self-propelled particle systems.
• Sedimentation in terrestrial experiments limits the study of three-dimensional dynamics.
• Janus particles offer a tunable platform for investigating active matter.

Purpose of the Study:

• To develop and validate an automated experiment module for microgravity studies of colloidal Janus particles.
• To investigate the active Brownian motion of light-driven Janus particles under weightlessness conditions.
• To enable systematic studies of control parameter effects on particle dynamics.

Main Methods:

• Design and implementation of the RAMSES (RAndom Motion of SElf-propelled particles in Space) module for the MAPHEUS sounding rocket.
• Utilizing a novel, high-power LED-based light source for homogeneous particle excitation.
• Employing ten independent sample cells for controlled variation of parameters like light intensity and particle concentration.
• Recording transmitted light intensities for post-flight analysis using differential dynamical microscopy.

Main Results:

• Successful deployment and operation of the RAMSES module in microgravity.
• Demonstration of light-induced self-propulsion and active Brownian motion of Janus particles.
• Acquisition of data suitable for detailed post-flight analysis of particle dynamics.

Conclusions:

• The RAMSES module is a viable platform for microgravity research on active matter.
• Weightlessness conditions effectively eliminate sedimentation, allowing for true 3D dynamics studies.
• The developed LED light source offers an efficient and compact alternative for particle excitation.