Hybrid colloidal microswimmers through sequential capillary assembly

Abstract

Active colloids, also known as artificial microswimmers, are self-propelled micro- and nanoparticles that convert uniform sources of fuel (e.g. chemical) or uniform external driving fields (e.g. magnetic or electric) into directed motion by virtue of asymmetry in their shape or composition. These materials are currently attracting enormous scientific attention as models for out-of-equilibrium systems and with the promise to be used as micro- and nanoscale devices. However, current fabrication of active colloids is limited in the choice of available materials, geometries, and modes of motion. Here, we use sequential capillarity-assisted particle assembly (sCAPA) to link microspheres of different materials into hybrid clusters of prescribed shapes ("colloidal molecules") that can actively translate, circulate and rotate powered by asymmetric electro-hydrodynamic flows. We characterize the active motion of the clusters and highlight the range of parameters (composition and shape) that can be used to tune their trajectories. Further engineering provides active colloids that switch motion under external triggers or perform simple pick-up and transport tasks. By linking their design, realization and characterization, our findings enable and inspire both physicists and engineers to create customized active colloids to explore novel fundamental phenomena in active matter and to investigate materials and propulsion schemes that are compatible with future applications.

Large scale micro-photometry for high resolution pH-characterization during electro-osmotic pumping and modular micro-swimming

“…Both types of information would significantly enhance possibilities of further modeling. In principle, similar analysis may also apply for asymmetric particles in AC electric fields, where electro-osmosis and electro-hydrodynamics induce the assembly of asymmetric particles [59][60][61].…”

Capillary Assembly of Liquid Particles

“…Template‐directed capillary assembly of colloidal particles [ 1 ] precisely controls the placement of nano/microscale objects into surface patterns for the generation of nano/microarrays and colloidal superstructures. [ 2–5 ] The method entails evaporation of particle suspensions comprised of polymer colloids, [ 6–10 ] metallic nanoparticles, [ 11–18 ] or biomolecules [ 19–21 ] onto rigid or elastomeric substrates patterned with ordered cavities. Both 2D and 3D microarrays and colloidal clusters ensue with potential uses as optical materials, photonic bandgap structures, sensors, and substrates for epitaxial growth of more complex colloidal materials.…”

Clustering-induced velocity-reversals of active colloids mixed with passive particles

“…Besides a range of theoretical studies focusing on motility-induced phase separation in active-passive mixtures [11][12][13][14] occurring at moderate densities, recent experiments [15][16][17][18][19] have observed the formation of various self-assembled structures even at very low active particle densities. Since these structures resemble those of ordinary molecules, the emerging clusters are called heteronuclear active colloidal molecules [20][21][22][23][24][25][26][27][28][29][30][31][32][33] . Ref.…”