Active Patchy Colloids with Shape-Tunable Dynamics

Abstract

Controlling the complex dynamics of active colloidsthe autonomous locomotion of colloidal particles and their spontaneous assemblyis challenging yet crucial for creating functional, out-of-equilibrium colloidal systems potentially useful for nano- and micromachines. Herein, by introducing the synthesis of active “patchy” colloids of various low-symmetry shapes, we demonstrate that the dynamics of such systems can be precisely tuned. The low-symmetry patchy colloids are made in bulk via a cluster-encapsulation-dewetting method. They carry essential information encoded in their shapes (particle geometry, number, size, and configurations of surface patches, etc.) that programs their locomotive and assembling behaviors. Under AC electric field, we show that the velocity of particle propulsion and the ability to brake and steer can be modulated by having two asymmetrical patches with various bending angles. The assembly of monopatch particles leads to the formation of dynamic and reconfigurable structures such as spinners and “cooperative swimmers” depending on the particle’s aspect ratios. A particle with two patches of different sizes allows for “directional bonding”, a concept popular in static assemblies but rare in dynamic ones. With the capability to make tunable and complex shapes, we anticipate the discovery of a diverse range of new dynamics and structures when other external stimuli (e.g., magnetic, optical, chemical, etc.) are employed and spark synergy with shapes.

Synthesis of ABn-type colloidal molecules by polymerization-induced particle-assembly (PIPA)

“…Colloidal molecules (CMs) are well-dened colloidal clusters with precise symmetry of molecular structures and have drawn extensive interest because of their unique properties 1,2 and potential as building blocks for low-coordination open structures. 3,4 With compartmental functional domains and directional interaction, CMs are promising in biological and medical applications, 5,6 self-assembly, 7,8 physical chemistry, [9][10][11] and materials science and technology. [12][13][14] Through particle-based self-assembly, CMs with molecule-like symmetries are enabled using monodisperse patchy building blocks with a suitable shape or interaction anisotropy.…”

Active colloidal molecules assembled via selective and directional bonds

“…Having shown the size-selective bonding based on simple spheres, we seek to build (selective and) directional bonds by utilizing anisotropic particles as ligands, in our case metallodielectric patchy particles each having a metallic (gold) lobe and a dielectric (polymer) lobe. The patchy particles are synthesized via a surfactant-aided dewetting method we recently developed 59 . The size of the two lobes and the particle's aspect ratio can be independently addressed (Supplementary Fig.…”

“…In these examples, we note that the combination of selective directional bonds and particle activity is even more critical and requires complex particles to carry all the necessary information. The use of particles with multiple patches and tunable shapes and compositions may provide a solution 59 . In all cases, fine control of the interparticle interactions, including both the static and dynamic ones, is key.…”

Catalytically propelled 3D printed colloidal microswimmers

“…One such study showed that L-shaped particles exhibit circular trajectories. 22 More recent experiments on select anisotropic shapes or patches confirmed some of the predictions in 2D [23][24][25][26] and found unexpected motion patterns such as non-cylindrical helices 27 in 3D. Still, the current limitations in particle design prevent a systematic comparison with theory.…”