Density Modulations in Active Colloidal Systems through Orthogonal Propulsion Control and Sensory Delays

Area of Science:

• Colloidal science
• Active matter physics
• Microfluidics

Background:

• Active colloidal systems and synthetic microswimmers are inspired by biological counterparts.
• Current systems often require external control for adaptive motility.
• Autonomous self-regulation in response to environmental stimuli is a key challenge.

Purpose of the Study:

• To develop Janus microswimmers with autonomous adaptive propulsion.
• To investigate the response of these microswimmers to varying illumination and chemical agents.
• To explore the role of sensory delay in microswimmer behavior and localization.

Main Methods:

• Fabrication of Janus microparticles (silica/titania).
• Utilizing electrohydrodynamic flows and induced-charge electrophoresis for propulsion.
• Applying uniform AC electric fields and UV illumination.
• Introducing chemical agents (methanol) to alter particle dynamics.

Main Results:

• Janus microswimmers demonstrated light-dependent propulsion velocity regulation.
• Photoconductivity of titania enabled autonomous speed adjustment under UV light.
• A finite sensory delay in velocity adaptation was observed.
• Particles showed concentration-dependent response time adaptation to methanol.
• Enhanced microswimmer localization was achieved due to sensory delay.

Conclusions:

• Developed microswimmers exhibit autonomous adaptation to environmental stimuli (light, chemicals).
• Sensory delay enhances localization, mimicking biological microswimmer strategies.
• Potential for novel adaptive active matter systems and microdevices.