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Extremely Long-Range Light-Driven Repulsion of Porous Microparticles.
David Feldmann1, Pooja Arya1, Taras Y Molotilin2
1Institute of Physics and Astronomy, University of Potsdam, 14476 Potsdam, Germany.
Langmuir : the ACS Journal of Surfaces and Colloids
|February 20, 2020
Summary
Researchers demonstrated remote control of particle interactions using light. Porous particles exhibit long-range repulsion via light-induced diffusio-osmotic flow, enabling tunable 2D assembly control.
Area of Science:
- Colloid and Surface Science
- Soft Matter Physics
- Nanotechnology
Background:
- Colloidal dispersion stability relies on short-range repulsive forces like electrostatic and steric interactions.
- Controlling particle interactions typically requires physical manipulation or environmental changes.
- Existing methods for controlling inter-particle forces have limited range and flexibility.
Purpose of the Study:
- To investigate the remote control of repulsive interactions between sedimented microsized particles using light.
- To explore the effect of photosensitive ionic surfactants on particle interactions under illumination.
- To determine if light can induce long-range repulsive forces in particle systems.
Main Methods:
- Utilizing aqueous electrolyte solutions with small additives of a photosensitive ionic surfactant.
- Sedimenting microsized particles onto a solid surface and illuminating with specific wavelengths.
- Comparing the interaction behavior of conventional impermeable particles versus porous particles under light.
- Analyzing the generation of diffusio-osmotic flow near porous particles.
Main Results:
- Conventional impermeable particles showed no significant change in interaction upon illumination.
- Porous particles exhibited a long-range repulsion, orders of magnitude greater than equilibrium surface forces.
- This repulsion was attributed to light-induced diffusio-osmotic flow, where porous particles acted as micropumps.
- Demonstrated reversible switching between densely packed aggregates and periodic lattices using two different wavelengths.
Conclusions:
- Light can remotely control inter-particle repulsive forces in systems with porous particles and photosensitive surfactants.
- Diffusio-osmotic flow generated by porous particles is the mechanism for light-induced long-range repulsion.
- This phenomenon offers a novel method for remote, tunable control of two-dimensional particle assemblies on surfaces.
