Related Experiment Video
Updated: Feb 2, 2026
09:26
Synthesis and Characterization of Supramolecular Colloids
Published on: April 22, 2016
10.5K
Diffusiophoretic design of self-spinning microgears from colloidal microswimmers
Antoine Aubret1, Jérémie Palacci
1Department of Physics, University of California, San Diego, USA. aaubret@ucsd.edu.
Soft Matter
|November 21, 2018
Summary
Researchers developed a new method to assemble microscopic machines using light-activated microswimmers. This strategy controls self-assembly and creates self-spinning microgears by harnessing diffusiophoretic interactions.
Area of Science:
- Colloid and Interface Science
- Active Matter Physics
- Materials Science
Background:
- Hierarchical self-assembly of microscopic machines from dissipative building blocks is key for novel active materials.
- Previous work demonstrated self-assembly of phoretic microswimmers into self-spinning microgears synchronized by diffusiophoretic interactions.
- Controlling self-assembly and building machines using phoretic phenomena requires advanced imaging and characterization techniques.
Purpose of the Study:
- To present a pedagogical strategy for controlling self-assembly and building machines using phoretic phenomena.
- To introduce Highly Inclined Laminated Optical sheets (HILO) microscopy for characterizing anisotropic and dynamic diffusiophoretic interactions.
- To demonstrate the rational design of machines by controlling phoretic phenomena.
Main Methods:
- Utilizing a (haematite) photocatalytic material in a (hydrogen peroxide) fuel under various illumination patterns.
- Employing a model of diffusiophoresis to rationalize particle migration in concentration gradients.
- Using Highly Inclined Laminated Optical sheets (HILO) microscopy to image and characterize diffusiophoretic interactions.
- Designing phototactic microswimmers that respond to light intensity gradients.
Main Results:
- The dynamics of photocatalytic microswimmers in fuel were quantitatively described by a diffusiophoresis model.
- Phototactic microswimmers were designed to move towards light sources due to reorientation in light gradients.
- Self-spinning microgears were assembled from microswimmers, with interactions characterized using HILO microscopy.
- Experimental results quantitatively agreed with analytical and numerical predictions.
Conclusions:
- Concentration gradients induced by chemical activity play a crucial role in controlling and designing interactions for self-assembly.
- The described approach is generic and provides a pathway for the rational design of machines by controlling phoretic phenomena.
- HILO microscopy is effective for characterizing dynamic diffusiophoretic interactions, overcoming limitations of conventional fluorescence microscopy.
Related Concept Videos
03:22Colloids
21.1K
Children at play often make suspensions such as mixtures of mud and water, flour and water, or a suspension of solid pigments in water known as tempera paint. These suspensions are heterogeneous mixtures composed of relatively large particles that are visible to the naked eye or can be seen with a magnifying glass. They are cloudy, and the suspended particles settle out after mixing. On the other hand, a solution is a homogeneous mixture in which no settling occurs and in which the dissolved...
21.1K
01:17Colloids and Suspensions
3.4K
Children at play often make suspensions such as mixtures of mud and water, flour and water, or a suspension of solid pigments in water known as tempera paint. These suspensions are heterogeneous mixtures composed of relatively large particles visible to the naked eye or seen with a magnifying glass. They are cloudy, and the suspended particles settle out after mixing. The suspended particles in a suspension settle out after some time of mixing. The separation of particles from a suspension is...
3.4K
01:09Colloidal precipitates
6.5K
The high insolubility of some precipitates can result in an unfavorable relative supersaturation. This can lead to colloidal particles with a large surface-to-mass ratio, where adsorption is promoted. For instance, in the precipitation of silver chloride, silver ions are adsorbed on the surface of the colloidal particles, forming a primary layer. This layer attracts ions of opposite charge (such as nitrate ions), forming a diffuse secondary layer of adsorbed ions. This electric double layer...
6.5K
01:08NMR Spectroscopy: Spin–Spin Coupling
3.2K
The spin state of an NMR-active nucleus can have a slight effect on its immediate electronic environment. This effect propagates through the intervening bonds and affects the electronic environments of NMR-active nuclei up to three bonds away; occasionally, even farther. This phenomenon is called spin–spin coupling or J-coupling. Coupling interactions are mutual and result in small changes in the absorption frequencies of both nuclei involved. While nuclei of the same element are involved...
3.2K
01:17Spin–Spin Coupling: One-Bond Coupling
1.5K
Coupling interactions are strongest between NMR-active nuclei bonded to each other, where spin information can be transmitted directly through the pair of bonding electrons. While nuclei polarize their electrons to the opposite spins, the bonding electron pair has opposite spins. Configurations with antiparallel nuclear spins are expected to be lower in energy. When coupling makes antiparallel states more favorable, J is considered to have a positive value. The one-bond coupling constant, 1J,...
1.5K
01:08Spin–Spin Coupling Constant: Overview
1.5K
In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must...
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must...
1.5K