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Patterning of Microorganisms and Microparticles through Sequential Capillarity-assisted Assembly

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Programming Tactic Behaviors of Active Colloids via Surface Charge.

Zuyao Xiao¹, Priyanka Sharan¹, Juliane Simmchen^1,2

¹Department of Physical Chemistry, Technische Universität Dresden, Dresden 01069, Germany.

|June 7, 2025

Summary

By altering colloid surface charges, researchers achieved programmable propulsion control in Janus micromotors. This breakthrough enables tunable tactic behaviors like chemotaxis and rheotaxis in active matter.

Keywords:

active colloids chemotaxis microfluidics phoretic mobility rheotaxis self-diffusiophoresis surface functionalization

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Area of Science:

Colloid and Interface Science
Active Matter Physics
Nanotechnology

Background:

Self-diffusiophoretic colloids exhibit autonomous motion driven by self-generated chemical gradients.
Phoretic slip, a surface fluid motion, dictates colloidal propulsion direction and depends on chemical gradients and phoretic mobility.

Purpose of the Study:

To investigate the effect of surface charge on the propulsion dynamics of Janus micromotors.
To demonstrate the tunability of tactic behaviors in active colloids through surface property modification.

Main Methods:

Modifying the surface charge of Janus micromotors.
Observing and analyzing the resulting changes in phoretic slip and propulsion direction.
Investigating responses to chemotactic and rheotactic stimuli.

Main Results:

Changing colloid surface charge successfully reversed the propulsion direction of Janus micromotors.
Surface charge tuning enabled control over complex tactic behaviors, including chemotaxis and rheotaxis.
Demonstrated a method for creating programmable active colloids via subtle surface property adjustments.

Conclusions:

Surface charge is a critical parameter for controlling active colloid behavior.
Programmable active colloids can be engineered by tuning surface properties, advancing the field of active matter.
This work provides a foundation for designing sophisticated micro- and nanomachines.