Magnetically Modulated Pot‐Like MnFe₂O₄ Micromotors: Nanoparticle Assembly Fabrication and their Capability for Direct Oil Removal

Abstract

This work demonstrates a simple‐structured, low‐cost magnetically modulated micromotor of MnFe2O4 pot‐like hollow microparticles as well as its facile, versatile, and large‐scale growing‐bubble‐templated nanoparticle (NP) assembly fabrication approach. In this approach, the hydrophobic MnFe2O4@oleic acid NPs in an oil droplet of chloroform and hexane assembled into a dense NP shell layer due to the hydrophobic interactions between the NP surfaces. With the encapsulated oil continuously vaporizing into high‐pressured gas bubbles, the dense MnFe2O4 NP shell layer then bursts, forming an asymmetric pot‐like MnFe2O4 micromotor by creating a single hole in it. For the as‐developed simple pot‐like MnFe2O4 micromotor, the catalytically generated O2 molecules nucleate and grow into bubbles preferentially on the inner concave surface rather than on the outer convex surface, resulting in continuous ejection of O2 bubbles from the open hole to propel it. Dexterously integrating the high catalytic activity for H2O2 decomposition to produce O2 bubbles, excellent magnetic property with the instinctive surface hydrophobicity, the MnFe2O4 pot‐like micromotor not only can autonomously move in water media with both velocity and direction modulated by external magnetic field but also can directly serve for environmental oil removal without any further surface modification. The results here may inspire novel practical micromotors.

Forecastable and Guidable Bubble‐Propelled Microplate Motors for Cell Transport

“…The possibility of microplate motor guidance with magnetic particles is in line with recent works of others, reporting guided capsules, magnetically driven artificial bacteria flagella, Janus particles, pots, tubes, cell propulsion systems, as well as composite layered thin films . The cell–microplate agglomerates are not only able to be guided; they are also able to collide with a second cell.…”

“…The microplate motion direction can be controlled with a magnet due to incorporated superparamagnetic iron oxide nanoparticles . It is noted that no fully magnetic motion like in refs . is possible due to too‐low magnetite concentration.…”

“…[27,28] It is noted that no fully magnetic motion like in refs. [29,30] is possible due to too-low magnetite concentration. The motion pattern and speed were compared with analytical and numerical simulations of refs.…”

Microbots Decorated with Silver Nanoparticles Kill Bacteria in Aqueous Media

“…[10][11][12] In addition, they contain many surface functionalities 13 which open new opportunities to develop micro and nanodevices as efficient tools for water cleaning. [14][15][16] Currently, micromotors have been developed for the efficient degradation of organic pollutants, 12,17-20 chemical warfare agents 11,21 and the capture of organic and inorganic [22][23][24][25][26][27][28][29] pollutants, such as heavy metals. 29 New bactericidal micromotors [30][31][32] are recently being developed as new efficient tools for cleaning waterborne bateria due to the increasing threat of antibiotic resistant bacteria and the harmful chemical byproducts generated by conventional water disinfection methods.…”

Nanoparticle‐Shelled Catalytic Bubble Micromotor

“…Several viable motive mechanisms have been identified outside the realm of biological motility such as self‐electrophoresis, self‐diffusiophoresis, dynamic surface/interfacial tension, and bubble recoiling . Moreover, it is widely believed that micro‐ and nanomachines can address and solve numerous challenges involving transport, assembly of cargo payloads, delivery of drugs, analytical chemistry, water treatment, and oil removal, to name a few examples. However, micromotors typically consist of materials whose density and weight are higher than that of the liquids they are dispersed in, causing the micromachines to sediment and sink in the media.…”