Reconfigurable magnetic microrobot swarm: Multimode transformation, locomotion, and manipulation

Abstract

Swimming microrobots that are energized by external magnetic fields exhibit a variety of intriguing collective behaviors, ranging from dynamic self-organization to coherent motion; however, achieving multiple, desired collective modes within one colloidal system to emulate high environmental adaptability and enhanced tasking capabilities of natural swarms is challenging. Here, we present a strategy that uses alternating magnetic fields to program hematite colloidal particles into liquid, chain, vortex, and ribbon-like microrobotic swarms and enables fast and reversible transformations between them. The chain is characterized by passing through confined narrow channels, and the herring school–like ribbon procession is capable of large-area synchronized manipulation, whereas the colony-like vortex can aggregate at a high density toward coordinated handling of heavy loads. Using the developed discrete particle simulation methods, we investigated generation mechanisms of these four swarms, as well as the “tank-treading” motion of the chain and vortex merging. In addition, the swarms can be programmed to steer in any direction with excellent maneuverability, and the vortex’s chirality can be rapidly switched with high pattern stability. This reconfigurable microrobot swarm can provide versatile collective modes to address environmental variations or multitasking requirements; it has potential to investigate fundamentals in living systems and to serve as a functional bio-microrobot system for biomedicine.

Self-Propelled Janus Microdimer Swimmers under a Rotating Magnetic Field

“…For a 5 + 5 µm microdimer swimmer, the speed increased linearly with the driving frequency and reached a maximum velocity of 133 µm•s −1 (≈13.3 body length s −1 ) at 32 Hz, further increasing the frequency reduced the velocity. Such a maximum synchronized frequency is called step-out frequency which was also commonly observed for many other types of micromotors in rotating and oscillating magnetic fields [44,70,71]. The reason we speculate for this variation is the occurrence of out-of-step phenomenon and the increase in drag caused by the increasing speed.…”

Robust boundary flow in chiral active fluid

“…, 14] and sperm cells [4,15] near surfaces, and magnetotactic bacteria in rotating fields [16,17]. Artificial chiral active systems have also been developed, such as colloids [18][19][20][21][22][23][24], millimeter-scale magnets [25,26] and rotating granular particles [27][28][29][30]. Multiple numerical and theoretical studies on chiral active fluid have been carried out [27,[31][32][33][34][35][36][37][38].…”

Efficient Navigation of Colloidal Robots in an Unknown Environment via Deep Reinforcement Learning

“…Our DRL architecture can also be used as a basic building block to construct more complex learning architectures for navigation tasks in more challenging environments, including incorporating additional visual channels for navigation in flow fields, adding memory module for navigation in nonstationary environments with limited visibility, using 3D convolutional layers for 3D navigation, extending to continuous control DRL for high‐precision localization tasks, and building hierarchical neural networks for navigation in environments with multiple‐scale obstacle features. Our algorithm can also be extended to a multiagent system to control multiple robots to cooperate on tasks and assemble to nonequilibrium machines and devices or applied as a general end‐to‐end controller for controlling stochastic colloidal assembly . Ultimately, our DRL algorithm allows to be integrated with experimental systems as it can directly process raw sensor inputs of microrobot systems (e.g., microscope) .…”