Shape-directed dynamics of active colloids powered by induced-charge electrophoresis

Abstract

The symmetry and shape of colloidal particles can direct complex particle motions through fluid environments powered by simple energy inputs. The ability to rationally design or "program" the dynamics of such active colloids is an important step toward the realization of colloidal machines, in which components assemble spontaneously in space and time to perform dynamic (dissipative) functions such as actuation and transport. Here, we systematically investigate the dynamics of polarizable particles of different shapes moving in an oscillating electric field via induced-charge electrophoresis (ICEP). We consider particles from each point group in three dimensions (3D) and identify the different rotational and translational motions allowed by symmetry. We describe how the 3D shape of rigid particles can be tailored to achieve desired dynamics including oscillatory motions, helical trajectories, and complex periodic orbits. The methodology we develop is generally applicable to the design of shape-directed particle motions powered by other energy inputs.

Supercolloidal Spinners: Complex Active Particles for Electrically Powered and Switchable Rotation

“…Similar to the nonpatchy microspinners, the particles spin clockwise at low frequencies, but in this case, the transition to anticlockwise rotation occurs at ≈0.3 kHz instead of 3.0 kHz. As the frequency increases further (i.e., to ≈3.0 kHz), the microspinners switch their direction of rotation again to clockwise . As the frequency increases further still (i.e., to ≈50 kHz), the microspinners switch their direction of rotation one final time .…”

Cargo capture and transport by colloidal swarms

“…1A): (i) sensing the system state via particle tracking, i.e., the self-propelled particle positions and orientations and cargo position; (ii) calculating self-propulsion speeds of each particle based on the current state and desired future state (based on a control objective); and (iii) actuating each particle's speed by considering light-activated self-propelled colloids on a light array [e.g., a liquid-crystal display (35) screen surface]. Actuation could also be achieved on spatially addressable electrodes or other arrays that mediate locally actuated transport mechanisms (36)(37)(38)(39), which could modify some terms of the dynamic model, but the control problem would be conceptually similar.…”

Leveraging collective effects in externally driven colloidal suspensions: experiments and simulations

“…Recent theoretical work by Brooks et al highlights the potential of using shape to create directed motion with ICEP flows. They present a systematic investigation of dynamics as a function of particle symmetry, demonstrating that essentially any dynamic function (transitional/rotational motion) can be achieved by using an appropriately shaped colloid [89]. We hope this work inspires follow up experimental work, creating driven suspensions with new properties.…”

“…One exciting avenue of recent work is the study of non-spherical/asymmetric colloidal particles. Significant advances have been made in individual particle fabrication [164,165,166,118,114,167,168,107,89,169], and there is still much room to explore the influence of particle shape on collective dynamics. Exploring shape asymmetry opens the possibility to engineer particles to achieve a given individual or collective behaviour, such as swarming, mixing, advection, or suspension rheology.…”

“…Understanding the interaction of particles with complex boundaries is a crucial ingredient for mimicking real-world transport. 5. outstanding interest: [89] Systematic theoretical study of shape effects in ICEP propulsion.…”