Magnetic manipulation of self-assembled colloidal asters

Abstract

Self-assembled materials must actively consume energy and remain out of equilibrium to support structural complexity and functional diversity. Here we show that a magnetic colloidal suspension confined at the interface between two immiscible liquids and energized by an alternating magnetic field dynamically self-assembles into localized asters and arrays of asters, which exhibit locomotion and shape change. By controlling a small external magnetic field applied parallel to the interface, we show that asters can capture, transport, and position target microparticles. The ability to manipulate colloidal structures is crucial for the further development of self-assembled microrobots.

Structured light enables biomimetic swimming and versatile locomotion of photoresponsive soft microrobots

“…These challenges mean that most artificial microrobots actually have no actuators. Rather, they are in most cases rigid monolithic structures, either pushed by chemical reactions 15 or directly manipulated by torques or forces applied by external magnetic fields [16][17][18][19][20] .…”

“…These challenges mean that most artificial microrobots actually have no actuators. Rather, they are in most cases rigid monolithic structures, either pushed by chemical reactions 15 or directly 4 manipulated by torques or forces applied by external magnetic fields [16][17][18][19][20] .Alternatively, they consist of flexible materials embedding, at best, a small number of passive degrees of freedom (DOFs) 21,22 .In macroscale robots, one approach to increase the number of DOFs has been to adopt soft bodies, capable of biomimetic actuation [23][24][25][26][27][28] . However, these approaches have resisted miniaturization.…”

On-chip manipulation of single microparticles, cells, and organisms using surface acoustic waves

“…Although optical tweezers have demonstrated excellent precision and versatility for a number of functionalities, they have two potential shortcomings: First, they may cause physiological damage to cells and other biological objects from potential laser-induced heating, multiphoton absorption in biological materials, and the formation of singlet oxygen (8); and second, they rely on complex, potentially expensive optical setups that are difficult to maintain and miniaturize. Many alternative bioparticle-manipulation techniques (9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) have since been developed to overcome these shortcomings, however, each technique has its own potential drawbacks. For example, magnetic tweezers (17)(18)(19) require targets to be prelabeled with magnetic materials, a procedure that affects cell viability; electrophoresis/dielectrophoresis based methods (9)(10)(11)(20)(21)(22) are strictly dependent on particle polarizibility and medium conductivity and utilize electrical forces that may adversely affect cell physiology due to current-induced heating and/or direct electricfield interaction (23).…”

Flexible mechanism of magnetic microbeads chains in an oscillating field

“…[6][7][8][9][10][11] Magnetic actuation enables motion of the magnetic micro devises to be controlled wirelessly without affecting biological viability but with the extra benefit that the direction of motion can be determined by the field. 12,13 One of the challenges in proposing the micro devices to move in the low-Reynolds-number regime should be that a microswimmer must deform without structural instability in a way that is not invariant under time-reversal.…”