Controllable magnetic hybrid microswimmers with hollow helical structures are fabricated, by a facile strategy based on microfluidic template synthesis and biosilicification, to achieve enhanced rotation-based locomotion for cargo transport. The magnetic hybrid microswimmers are fabricated by first synthesizing Fe 3 O 4 -nanoparticles-containing helical Caalginate microfibers from microfluidics, followed with biosilicification and controllable dicing to engineer their rigid hollow helical structures. The microswimmers show hollow helical structures consisting of a rigid, biocompatible alginate/protamine/silica shell embedded with Fe 3 O 4 nanoparticles. Their helical structures can be engineered into open tubular structures or closed compartmental structures by using microfibers or diced microfibers as templates for biosilicification. Powered by a simple rotating magnet, the microswimmers can achieve enhanced rotation-based locomotion and provide good mechanical strength for supporting cargo for transportation. This work provides a simple and efficient strategy for fabricating controllable magnetic hybrid microswimmers with hollow helical structures to achieve enhanced rotationbased locomotion for cargo transport, encapsulation, and delivery.

No abstract

A facile and flexible approach is developed to fabricate bubble-propelled mesoporous micromotors carrying nanocatalysts for efficient water remediation. The micromotors are prepared by simply coating the hemispherical surface of Fe3O4-nanoparticle-containing mesoporous SiO2 microparticles with a polydopamine layer for decorating Ag nanoparticles, based on the versatile adhesion and reduction properties of polydopamine. The Fe3O4 nanoparticles can produce OH radicals from H2O2 for pollutant degradation via Fenton reaction, whereas the mesoporous SiO2 matrix provides large surface area with anchored Fe3O4 nanoparticles for improved degradation performance. Moreover, the Ag nanoparticles can decompose H2O2 into oxygen bubbles for powering the movement of micromotors to further enhance the pollutant degradation. The micromotors that synergistically integrate these functions enable efficient degradation of pollutants, such as methylene blue demonstrated in this work, for water remediation. This approach offers a simple and versatile strategy for creating micromotors with flexible compositions and structures for applications in water remediation, drug delivery, and cargo transport.

delivery, [1] drug release, [8] assembling, [9,10] packing, [11,12] and magnetic-driven motion. [13,14] For example, cylindrical microstructured materials self-assembled from copolymers can persist in the blood circulation of rodents ten times longer than their spherical counterparts. [2] Helical microstructured materials can convert rotational motion into translational motion in liquid media, such as water and blood, under remote control of a rotated magnetic field, showing great potential for many applications. [13,15] With such unique motion behaviors, helical microstructured materials can be utilized for uses such as picking and placing of microcargo, [14] mixing and pumping of fluid, [16] remote sensing of pH, [17] drilling of bovine tissues, [18] and cancer hyperthermia. [19] Thus, creation of uniform microstructured materials with versatile nonspherical and helical shapes is crucial for achieving advanced functions.Generally, microstructured materials with nonspherical and helical shapes can be produced by methods such as film-based extension of spherical microparticles, [20][21][22] mold-based template synthesis, [23,24] microfluidic-based template synthesis, [8,[25][26][27] and polymerization induced by 3D direct laser writing. [14] For example, incorporation of polystyrene-based microparticles in polymeric film, followed with 1D or 2D film extension, can produce various nonspherical microparticles. [20][21][22] By confining precursor solutions in differently shaped microwells of molds, nonspherical microparticles with flexible shapes can also be produced. [23,24] With excellent manipulation of microflows, [28][29][30] microfluidic technique provides a powerful platform for fabricating nonspherical microparticles with versatile structures and compositions. [26,31,32] Mask-assisted selective polymerization of photo-curable solution in microchannel can fabricate nonspherical microparticles with flexible shapes depending on their mask, [25,33] and the flow configuration. [34,35] Alternatively, monodisperse emulsion droplets from microfluidics, with versatile shapes, provide excellent templates for engineering uniform nonspherical microparticles. Deformed droplets confined by microchannel with different dimensions, [26,27] Janus droplets with one curable hemisphere, [31,36] and evolved acorn-shaped droplets from double emulsions, [32] can be generated from microfluidics for fabricating nonspherical microparticles with different shapes. However, for the above-mentioned methods, it is difficult to produce microstructured materials with complex Microstructured MaterialsThis work reports on a facile and flexible strategy based on the deformation of encapsulated droplets in fiber-like polymeric matrices for template synthesis of controllable microstructured materials from nonspherical microparticles to complex 3D helices. Monodisperse droplets generated from microfluidics are encapsulated into crosslinked polymeric networks via an interfacial crosslinking reaction in microchannel to in situ produce the droplet-...

No abstract