Assembling particle clusters with incoherent 3D magnetic fields

Coiling of semiflexible paramagnetic colloidal chains

“…33,34 Leveraging the dynamics of these driven colloidal systems is crucial for the propulsion of micro-robots, 32,35 the pumping of particulates in microfluidic devices by mimicking ciliary strokes, 21,[36][37][38] as well as the loading and transportation of cargo to targeted sites. 39,40 The most common approach to actuate semiflexible paramagnetic chains is to use an in-plane circularly rotating magnetic field (CRMF), 25,41,42 which changes direction while maintaining a constant magnitude. The parameters of the CRMF define the interplay between viscous and magnetic stresses acting on the chains.…”

2D colloids in rotating electric fields: A laboratory of strong tunable three-body interactions

“…As a result, the magnitude of three-body interactions with respect to the pairwise ones can be approximately characterised as ∝ λ. For instance, in the case of silica vs iron oxide particles in water |λ SiO2 /λ Fe3O4 | 2.2 (see Materials and Methods) the three-body forces are enhanced by more than a factor or two, suggesting that the tunable interactions between the colloids in rotating electric fields can provide unprecedentedly strong three-body part, unavailable in other model systems (including magnetic ones [53][54][55][56][57][58][61][62][63][64]). However, neither the tunable interactions nor phase transitions in colloids in rotating electric fields have ever been studied.…”

Effective Structure Control of Colloidal Molecules and the Morphology Evolution Mechanism Investigation

“…Controlled clustering method enables preformed colloids to assemble into cluster by physical pathways (e.g., depletion interaction, capillary condensation, van der Waals forces, electrostatic interactions, structural forces, and external fields), chemical pathways (e.g., chemical bonding), geometrical confinement (e.g., 2D/3D geometrical confinement) or coalescence. − In recent years, there have been a large number of DNA hybridization-based chemical bond-assisted control clustering methods to assemble Au or Ag colloids into various morphologic colloidal molecules. Up to now, there are three main ways to prepare CMs based on DNA hybridization: (1) CMs from hybridization between Au colloids functionalized by single-stranded DNA (ssDNA) and complementary ssDNA labeled with Au colloid; (2) the complementary ssDNAs were hybridized to form a scaffold and then Au colloids were assembled on the scaffold through gold–sulfur bonds; (3) in the complementary three-strand system, the nanoparticles were modified with two noncomplementary SSDNAs, respectively, and the third ssDNA could bridge them to form more complex colloidal molecules. , Zhu et al have recently prepared DNA-interconnected colloidal molecules using chemical bond-assisted control clustering methods, which were formed mainly by linking 10–30 nm gold nanoparticles with azobenzene-modified DNA strands …”