Biofilm is difficult to thoroughly cure with conventional antibiotics due to the high mechanical stability and antimicrobial barrier resulting from extracellular polymeric substances. Encouraged by the great potential of magnetic micro-/nanorobots in various fields and their enhanced action in swarm form, we designed a magnetic microswarm consisting of porous Fe3O4 mesoparticles (p-Fe3O4 MPs) and explored its application in biofilm disruption. Here, the p-Fe3O4 MPs microswarm (p-Fe3O4 swarm) was generated and actuated by a simple rotating magnetic field, which exhibited the capability of remote actuation, high cargo capacity, and strong localized convections. Notably, the p-Fe3O4 swarm could eliminate biofilms with high efficiency due to synergistic effects of chemical and physical processes: (i) generating bactericidal free radicals (•OH) for killing bacteria cells and degrading the biofilm by p-Fe3O4 MPs; (ii) physically disrupting the biofilm and promoting •OH penetration deep into biofilms by the swarm motion. As a demonstration of targeted treatment, the p-Fe3O4 swarm could be actuated to clear the biofilm along the geometrical route on a 2D surface and sweep away biofilm clogs in a 3D U-shaped tube. This designed microswarm platform holds great potential in treating biofilm occlusions particularly inside the tiny and tortuous cavities of medical and industrial settings.

The increasing accumulation of heavy metal ions in our surroundings is posing a serious threat to living systems. Adsorption means based on a variety of micro/nanomaterials and micro/nanomanipulation are being employed for fast and highly efficient removal of various pollutants. Here, a kind of biohybrid adsorbents is developed through in situ growing magnetic Fe3O4 nanoparticles on hydrothermally‐treated fungi spores. Such organic/inorganic porous spore@Fe3O4 biohybrid adsorbents (PSFBAs) can effectively adsorb and remove heavy metal ions due to porous structuring and high‐adsorbing components. Once combined with a magnetically‐driven microrobotic technique, magnetic PSFBAs in controllably collective motion show enhanced adsorption capacity and shorter removal time for multiple heavy metal ions compared to nonmotile counterparts. The corresponding magnetic actuation of collective PSFBAs swarming into a narrow fluidic channel is demonstrated. When utilizing these adsorbents together with magnetically‐propelled swarming microrobotic technique, lead ions in contaminated water are rapidly removed from 5 ppm down to 0.9 ppm, superior to untreated and static counterparts. Furthermore, such magnetically‐propelled PSFBAs can be reused after facile separation and post‐treatment, which is demonstrated by four consecutive cycles. The combination of biological entities and swarming microrobotic techniques would provide a promising avenue for the decontamination of pollutants in environmental remediation.

Swarm behaviors are nature’s strategies for performing cooperative work, and extensive research has been aimed at emulating these strategies in engineering systems. However, the implementation of vertical motion and construction of a 3D structure are still challenging. Herein, we propose a simple strategy for creating a hybrid-driven paramagnetic tornado-like microswarm in an aqueous solution by integrating the use of a magnetic field and light. The precession of a magnetic field results in in-plane rotation, and light promotes the conversion of a planar microswarm to a microswarm tornado, thus realizing the transition from 2D to 3D patterns. This 3D microswarm is capable of performing reversible, vertical mass transportation. The reconfigurable collective behavior of the swarm from 2D to 3D motion consists of rising, hovering, oscillation, and landing stages. Moreover, this 3D tornado-like microswarm is capable of controlling the chemical reaction rate of the liquid in which it is deployed, for example, the degradation of methylene blue. The experimental results unveil that the tornado-like microswarm can enhance the overall degradation while holding the reactant nearby and inside it because of the flow difference between near and far regions of the microswarm tornado. Furthermore, by applying an oscillating magnetic field, the 3D microswarm can process the trapped methylene blue for on-demand degradation. The microswarm tornado is demonstrated to provide a method for collective vertical transportation and inspire ideas for mimicking 3D swarm behaviors in order to apply the functional performance to biomedical, catalytic, and micro-/nanoengineering applications.

Coalescence and splitting of liquid marbles (LMs) are critical for the mixture of precise amount precursors and removal of the wastes in the microliter range. Here, the coalescence and splitting of LMs are realized by a simple gravity‐driven impact method and the two processes are systematically investigated to obtain the optimal parameters. The formation, coalescence, and splitting of LMs can be realized on‐demand with a designed channel box. By selecting the functional channels on the device, gravity‐based fusion and splitting of LMs are performed to mix medium/drugs and remove spent culture medium in a precise manner, thus ensuring that the microenvironment of the cells is maintained under optimal conditions. The LM‐based 3D stem cell spheroids are demonstrated to possess an approximately threefold of cell viability compared with the conventional spheroid obtained from nonadhesive plates. Delivery of the cell spheroid to a hydrophilic surface results in the in situ respreading of cells and gradual formation of typical 2D cell morphology, which offers the possibility for such spheroid‐based stem cell delivery in regenerative medicine.

SummaryCombining catalysts with active colloidal matter could keep catalysts from aggregating, a major problem in chemical reactions. We report a kind of ensemble of bubble-cross-linked magnetic colloidal swarming nanomotors (B-MCS) with enhanced catalytic activity because of the local increase of the nanocatalyst concentration and three-dimensional (3D) fluid convection. Compared with the two-dimensional swarming collective without bubbles, the integral rotation was boosted because of the dynamic dewetting and increased slip length caused by the continuously ejected tiny bubbles. The bubbles cross-link the nanocatalysts and form stack along the vertical axis, generating the 3D network-like B-MCS ensemble with high dynamic stability and low drag resistance. The generated B-MCS ensemble exhibits controllable locomotion performance when applying a rotating magnetic field. Benefiting from locally increased catalyst concentration, good mobility, and 3D fluidic convection, the B-MCS ensemble offers a promising approach to heterogeneous catalysis.