Reconfigurable Disk-like Microswarm under a Sawtooth Magnetic Field

Abstract

Swarming robotic systems, which stem from insect swarms in nature, exhibit a high level of environmental adaptability and enhanced tasking capabilities for targeted delivery and micromanipulation. Here, we present a strategy that reconfigures paramagnetic nanoparticles into microswarms energized by a sawtooth magnetic field. A rotary-stepping magnetic-chain mechanism is proposed to address the forming principle of disk-like swarms. Based on programming the sawtooth field, the microswarm can perform reversible transformations between a disk, an ellipse and a ribbon, as well as splitting and merging. In addition, the swarms can be steered in any direction with excellent maneuverability and a high level of pattern stability. Under accurate manipulation of a magnetic microswarm, multiple microparts with complicated shapes were successfully combined into a complete assembly. This reconfigurable swarming microrobot may shed light on the understanding of complex morphological transformations in living systems and provide future practical applications of microfabrication and micromanipulation.

Vector-Controlled Wheel-Like Magnetic Swarms With Multimodal Locomotion and Reconfigurable Capabilities

“…Accordingly, we present a strategy that reconfigures vertical swarms dynamically without leaving the original position by programming ‘butterfly’ swing fields ( Figure 5A ). Similar to the reconfiguration mechanism of horizontal disk-like swarm ( Zhang et al, 2021 ), vertical wheel-like swarm would also be elongated to ellipse-like swarm as the amplitude ratio γ is increased. During the reconstruction of rolling swarms, the contribution of translational displacement could be eliminated by symmetrically hovering motion as shown in Figure 5Aii .…”

“…Swarming micro-/nanorobots could be energized by different external stimuli, such as magnetic fields ( Yu et al, 2018a ; Li et al, 2015 ), chemicals ( Hu et al, 2020 ; Chang et al, 2019 ), electric fields ( Yan et al, 2016 ; Bricard et al, 2015 ), light ( Dong et al, 2018 ; Ibele et al, 2009 ), and ultrasound ( Xu et al, 2019 ; Xu et al, 2015 ). Inspired by the behavior of natural swarms, various dynamic patterns, such as liquid ( Xie et al, 2019 ), chain ( Martinez-Pedrero et al, 2015 ), ribbon ( Yu et al, 2018b ), vortex ( Yu et al, 2018a ; Kokot and Snezkho, 2018 ), and ellipse ( Yu J. et al, 2021 ; Zhang et al, 2021 ), have been reproduced by artificial swarming strategies. The design of these sophisticated swarming systems could potentially revolutionize the environmental, chemical and medical fields, such as pollution degradation ( Ji et al, 2020 ), heterogeneous catalysis ( Wang et al, 2019 ), active drug delivery ( Servant et al, 2015 ) and localized treatment of tumor ( Wang et al, 2018 ).…”

“…Magnetically actuated swarms may be a promising choice for the convenience and diversity of field generation and programming ( Yu S. et al, 2021 ; Li et al, 2018 ). Various actuation strategies have been successfully applied to trigger swarming micro-/nanorobots, such as rotating ( Servant et al, 2015 ), alternating ( Yu et al, 2018b ), conical ( Xie et al, 2019 ) and saw-tooth magnetic fields ( Zhang et al, 2021 ). However, practical biomedical applications of magnetic swarms are still challenging.…”

“…However, practical biomedical applications of magnetic swarms are still challenging. In the previous paper ( Zhang et al, 2021 ), we designed a disk-like microswarm energized by a saw-tooth magnetic field, which exhibited excellent pattern stability and was successfully applied to a precise micro-assembly practice. Similar to traditional “vortex” swarms, their collective behavior is characterized by two-dimensional (2D) planar motion on a flat substrate, which could be easily obstructed by 3D confinements or obstacles, such as slopes and narrow channels.…”

Spatiotemporally Actuated Hydrogel by Magnetic Swarm Nanorobotics

“…At the same time, micro/nanorobots as a whole can enhance the ability to perform delivery tasks, such as transporting and manipulating large cargoes. , Flexible shape shifts also make them more adaptable to complex environments to reach their targets at high speeds . These miniature nanorobot populations offer great potential in biomedical applications, such as biocatalysis, , in vivo imaging, − and micromanipulation, − and have become the most active research area in recent years, especially in targeted delivery. − …”