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Deformability and self‐adaptability are important for soft robots to deal with uncertain and varying situations and environments during movement and navigation. Droplet‐based robots are great candidates to travel inside narrow and constrained spaces without damaging the interfaces due to their extreme deformability and liquid nature, which enables smooth contact between robots and target spaces. Here, magnetic liquid metal droplet robots, comprising liquid metal and carbonyl iron, that can perform reversible telescopic deformation, bending, and on‐demand locomotion are proposed. The magnetic liquid‐metal‐based robots can perform on‐demand and reversible coalescence and splitting by intricately applying magnetic fields. Importantly, the liquid metal robot can perform phase transition to fix the desired shape after programmable shape encoding. The liquid‐metal‐based soft robots can serve as dynamic and recyclable switches for complex circuits, and are capable of repairing damaged sections of microcircuits by remote actuation, controllable coalescence, and on‐demand circuit welding. This technology provides a new application scenario of droplet‐based soft robots for on‐demand circuit welding and transient recyclable electronics. A preprint version of the article can be found at: https://www.authorea.com/doi/full/10.22541/au.165167005.56125584. [ABSTRACT FROM AUTHOR]

Penetration of cell membrane at micro/nano‐scale with untethered probe is of great scientific significance, yet still challenging. Here, a carbon nanocoil based magnetic nanorobot, which can precisely target single cell and perform cell membrane penetration, is reported. The nanorobots are as‐synthesized by chemical vapor deposition with high yield, followed by physical deposition of Ni and Au nanofilms. Rotating electromagnetic fields are used to steer the nanorobots to navigate following any pre‐designed path. The helical nanorobots can realize mechanical perforation of the plasma membrane and even nuclear envelope with precise position at the subcellular level. With the aid of the externally deposited Au nanofilm, surface enhanced Raman scattering bio‐sensing signals can be collected from cellular plasma and nucleus. Furthermore, the nanorobots demonstrate capability of efficient photothermal therapy against targeted cancer cells and serve as an integrated theranostic platform, providing promising prospects in future precision medicine. [ABSTRACT FROM AUTHOR]

The Fenton reaction, among one of the advanced oxidation processes, has been widely employed for water remediation. Here, we report using magnetic Fe3O4 nanoparticles to accelerate the degradation of the simulative organic pollutant (i. e. Rhodamine B) in a collective manner, featuring an enhanced Fenton reaction. Fe2+ ions released from Fe3O4 nanoparticles function as a reducing agent to trigger the Fenton reaction in an acidic environment. A large number of Fe3O4 nanoparticles form the microswarm by applying a rotating magnetic field, which would further improve the intermixing and reaction diffusion as a result of the hydrodynamic vortex created by magnetic chains. Moreover, the microswarm possesses the ability of targeted degradation achieved by the collective locomotion, and such a collective manner would ultimately avoid the loss of Fe3O4 nanoparticles during the whole process. Besides, Fe3O4 nanoparticles can be magnetically collected and rinsed for recycling use, with a retained dye degradation rate of 73.5% after 3 degradation cycles. As a result, the magnetic microswarm holds advantages in terms of low cost, enhanced degradation, recyclability, and targeted decontamination, which is promising for the removal of organic pollutants. [ABSTRACT FROM AUTHOR]

The nanomotors consisted of gold and ferric oxide in this study are driven by visible light. Actuation of nanomotors results from the comprehensive effect of diffusion and migration of species in solution. In view of electrons, internal and external electric fields of a gold/ferric oxide nanomotor are analyzed to show the propulsion mechanism based on self-electrophoresis, especially for electron distribution resulted from light illumination on the semiconductor part. Induced photovoltage triggers decomposition of hydrogen peroxide. Local electric field, formed by moving electrons in a nanomotor and charged particles in solution, drives protons to migrate as primary effect. However, the concentration gradient, impelling protons to move from ferric oxide to gold, works little in start and moving period. A gold/ferric oxide nanomotor model is established. Local moving environment of nanomotors varies and is shown by the proton concentration distribution, velocity field, and electric field. Light with wavelength shorter than 552.2 nm can actuate nanomotors, realizing start and stop control in visible light band. Stronger light intensity and lower wavelength result in higher velocity. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. Magnetic biohybrid adsorbents are developed through in situ growth of magnetic Fe3O4 nanoparticles on hydrothermally‐treated fungi spores. When combined with magnetically driven swarming microrobotic techniques, such biohybrid adsorbents show a high capacity for heavy metal adsorption, shorter removal time, easy separation, and cyclic usability. [ABSTRACT FROM AUTHOR]