Co-Assembly of Oppositely Charged Particles into Linear Clusters and Chains of Controllable Length

Abstract

Colloidal particles with strongly attractive interactions snap on contact and form permanent, but disordered aggregates. In contrast, AC electric fields allow directional assembly of chains or crystals from repulsive particles by dielectrophoresis (DEP), but these structures fall apart once the field is switched off. We demonstrate how well-organized, permanent clusters and chains of micron-sized particles can be assembled by applying DEP to mixtures of oppositely charged microspheres. We found that the length of the formed chains depends on size ratio as well as the number ratio of the two species, and formulated a statistical model for this assembly mechanism, which is in excellent agreement with the experimental results. The assembly rules resulting from this study form a basis for tailoring new classes of permanent supracolloidal clusters and gels.

Electric field driven self-assembly of ionic microgels

“…Taking into account the non-uniformities of the internal electric eld due to the presence of the particles themselves, the electric eld intensity is higher at the interstitial sites between particles in a chain. 37,38 This is believed to lead to a strengthening of the propensity for close-packed structures, and might affect the FCC-to-BCT transition quantitatively.…”

Nanocapillarity-mediated magnetic assembly of nanoparticles into ultraflexible filaments and reconfigurable networks

“…For example, particles organized in long-ranged structures by external fields 3,4 can be bound permanently into stiff chains through electrostatic or van der Waals attraction 4,5 , or into flexible chains through soft molecular linkers such as surface-grafted DNA or polymers 6–11 . Here, we show that capillarity-mediated binding between magnetic nanoparticles coated with a liquid lipid shell can be used for the assembly of ultraflexible microfilaments and network structures.…”

Colloidal analogs of molecular chain stoppers

“…It is currently well-established that a broad range of particles with two reactive patches, such as polymer microbeads (4), inorganic nanoparticles (5), and block copolymer micelles (6), act similar to bifunctional molecular monomers and organize themselves into one-dimensional polymer-like structures. The self-assembly of colloidal polymers can also be assisted by the application of an electric (7) or magnetic field (8). The analogy between chemical reactions and the self-assembly process offers a mutually beneficial approach: (i) the use of synthetic concepts as a strategy for controllable and quantitative self-assembly of colloidal particles into structures with well-defined sizes, spatial organization, and directionality and (ii) the development of fundamental knowledge about chemical reactions by visualizing colloidal assemblies.…”