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Scheme 1. (A) Schematic illustration of the PC template used to prepare GOx/Ni/Pt microtubes. A legend on the right shows the order of functional layers. (B) Operation of the MnO2-protected micromotors. After the removal of the PC template, the functional Au-layer was sputtered and modified with alkanethiols (R-SH). When the tube is submerged into the H2O2 solution, the MnO2 core gradually dissolves and bare Pt surface is exposed. For simplicity, the Ni layer is not shown.
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Platinum (Pt) based micromotors have shown many exciting applications when functionalized using gold-thiol chemistry. However, thiols are known to bind to the Pt surface, which can lead to serious deactivation of the catalyst. In this paper, we demonstrate that manganese oxide (MnO2) can be used to protect Pt based micromotors prior to the thiol tr...
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Citations
... While this 149 design seems a commercially viable solution for managing accidents out at sea, it is highly 150 desired to downsizing this protocol and studying their collective performance at micro-and 151 nanoscale. (Gao et al., 2013;Guix et al., 2012), Jänis's (Minh et al., 2017;Safdar et al., 2015), and Guan's and Mou's (Mou et al., 2015) research groups (Table 1). This contribution was significant thanks to the innovative design of electroplated catalytic microtubules (Gao et al., 2011), which endorsed an unprecedented ultrafast bubble thrust propulsion. ...
... The scale bar is 10 μm. Reproduced from Reference(Minh et al., 2017) with permission.Benefiting from previous discoveries on template-directed electrochemical deposition, Minh et al. further developed a fabrication protocol involving direct growth of microtubes containing graphene oxides, magnetic Ni layer, catalytic Pt layer, and catalytically active and protective MnO 2 core layer (Figure 5)(Minh et al., 2017). All the deposition could be carried out in a single electroplating cell, using aqueous plating solutions prepared from respective precursors. ...
... The scale bar is 10 μm. Reproduced from Reference(Minh et al., 2017) with permission.Benefiting from previous discoveries on template-directed electrochemical deposition, Minh et al. further developed a fabrication protocol involving direct growth of microtubes containing graphene oxides, magnetic Ni layer, catalytic Pt layer, and catalytically active and protective MnO 2 core layer (Figure 5)(Minh et al., 2017). All the deposition could be carried out in a single electroplating cell, using aqueous plating solutions prepared from respective precursors. ...
High-efficiency, safe and economically viable nano-engineered platforms for oil spill cleanup and recovery are of great importance. This review takes account of the concept of nanomotors and micromotors and their most advancements in use for oil spill treatment. The fundamental facets of artificial micro- and nano-machines/nanobots/nanomotors (MNMs) are first documented, followed by the most recent influencing developments in chemical engineering approaches toward their specific utilizations. The surface chemistry of these MNMs, their behaviors in different water matrices and their roles in the removal of oil are examined, revealing great rooms for improvement. The strategies for surface and structural modification of these tiny machines toward enhancing their reactivity in the removal of oil and coupled tasking are discussed in details, highlighting the significance of fit-for-duty design and tailored fabrication. The engineering limitations and practical implementation barriers of this emerging technology and how it can be overcome are also considered. Finally, some engineering boundaries and perspectives of this fast-evolving field are proposed at the end.
... An immediate challenge in the field of soft active matter (Ghose and Adhikari, 2014;Kim et al., 2014;Li et al., 2014a;Sengupta et al., 2014) is to synthesize self-propelling (Ma et al., 2016;Soto et al., 2016;Minh et al., 2017;Zhou et al., 2017) in a manner that is facile, preferably single step and that affords a rational control of motility. All such attributes can be built into colloidal charged metal oxide based soft-oxometalates (SOMs) (Roy, 2011(Roy, , 2014 due to the presence of redox sites on their diffuse interface. ...
The recent interest in self-propulsion raises an immediate challenge in facile and single-step synthesis of active particles. Here, we address this challenge and synthesize soft oxometalate nanomotors that translate ballistically in water using the energy released in a redox reaction of hydrazine fuel with the soft-oxometalates. Our motors reach a maximum speed of 370 body lengths per second and remain motile over a period of approximately 3 days. We report measurements of the speed of a single motor as a function of the concentration of hydrazine. It is also possible to induce a transition from single-particle translation to collective motility with biomimetic bands simply by tuning the loading of the fuel. We rationalize the results from a physicochemical hydrodynamic theory. Our nanomotors may also be used for transport of catalytic materials in harsh chemical environments that would otherwise passivate the active catalyst.
... Thus, the biosensors based on the speed as the signal output are instable. This can be alleviated by covering the Pt layer with a protective layer, such as MnO 2 layer [106] or a polymeric layer [107]. Besides, the sensitivity of these tubular Micro/Nanomotors-based biosensors is very low. ...
Micro/nanomotors are self-propelled machines that can convert various energy sources into autonomous movement. With the great advances of nanotechnology, Micro/Nanomotors of various geometries have been designed and fabricated over the past few decades. Among them, the tubular Micro/Nanomotors have a unique morphology of hollow structures, which enable them to possess a strong driving force and easy surface functionalization. They are promising for environmental and biomedical applications, ranging from water remediation, sensing to active drug delivery and precise surgery. This article gives a comprehensive and clear review of tubular Micro/Nanomotors, including propulsion mechanisms, fabrication techniques and applications. In the end, we also put forward some realistic problems and speculate about corresponding methods to improve existing tubular Micro/Nanomotors.
As emerging micro/nano‐scale devices, micro/nanomotors have been innovatively applied in the environmental and biomedical applications. In this paper, the recent advances of Mn‐based micro/nanomotors (Mn‐micro/nanomotors) in catalytic oxidation of organic contaminants and the mechanisms in decomposition of H2O2 (e.g., the generation of O2 bubbles and reactive oxygen species) are reviewed. The intrinsic characteristics and synthetic strategies of Mn‐based materials are discussed, aiming to gain comprehensive understandings on the asymmetric design of micro/nanomotors. Mn‐micro/nanomotors have many advantages such as flexible structures, biocompatibility, powerful motion, long lifetime, and low‐cost as compared to noble‐metal micro/nanomotors. These merits fulfil Mn‐micro/nanomotors great promises from proof‐of‐concept studies to realistic applications, including pollutant decomposition, trace detection of heavy metal ions, oil removal, drug delivery, isolation of biological targets, and killing bacteria and cancer cells. The great flexibility in fabrication enables diverse and innovative strategies to address challenges for Mn‐micro/nanomotors, including high consumption of H2O2 and non‐directional motion. Meanwhile, a perspective of Mn‐micro/nanomotors in water remediation by coupling the motors with other Fenton/Fenton‐like systems to enhance the catalytic activity and to yield more reactive oxygen species is presented. Directions to the design of on‐demand H2O2‐fueled Mn‐micro/nanomotors for advanced purification of organic contaminants in aquatic systems are also proposed.
We exploit electrolyte confinement effects in porous membranes to electrosynthesize a two-engine micromachine from a single electrolyte solution. Taking advantage of the often undesired overplating observed in template-assisted deposition, we can produce micromachines consisting of hollow microstructures with a compositionally graded mushroom-like shape that consist of a manganese oxide-based stipe and an iron oxide-based cap. While the stipe acts as the catalytic motor of the machine, the cap serves as a magnetic steering wheel.
Micro/nanomachines have attracted tremendous interest in chemo/bioanalytical science and environmental remediation due to the synergistic effect of unique motion characteristics and the inherited physicochemical properties from micro/nanomaterials. Past decade has witnessed great progresses on a wide array of micro/nanomachines with diverse functionalities for specific sensing and removal applications. The development of designed materials and structures, the exploration of new propulsion mechanism, and the realization of versatile functionalization are employed for potential applications. In this review, the recent advances in the exploration of functionalized micro/nanomachines are summarized, with special emphasis on the functionalization of micro/nanomachines and their corresponding sensing and removal capability. Possible challenges facing micro/nanomachines in sensing and removal application are discussed, accompanied with the extrapolated perspectives for the future focus.
Water contamination from industrial and anthropogenic activities is nowadays a major issue in many countries worldwide. To address this problem, efficient water treatment technologies are required. Recent efforts have focused on the development of self-propelled micromotors that provide enhanced micro-mixing and mass-transfer by the transportation of reactive species, resulting in higher decontamination rates. However, a real application of these micromotors is still limited due to the high cost associated to their fabrication process. Here, we present Fe2O3-decorated SiO2/MnO2 microjets for the simultaneous removal of industrial organic pollutants and heavy metals present in wastewater. These microjets were synthezised by low-cost and scalable methods. They exhibit an average speed of 485±32 µm s-1 (~28 body length s-1) at 7% H2O2, which is the highest reported for MnO2-based tubular micromotors. Furthermore, the photocatalytic and adsorbent properties of the microjets enable the efficient degradation of organic pollutants such as tetracycline and rhodamine B under visible light irradiation, as well as the removal of heavy metal ions such as Cd2+ and Pb2+.
Synthetic micro- and nanomotors (MNMs) are tiny objects that can autonomously move under the influence of an appropriate source of energy, such as a chemical fuel, magnetic field, ultrasound, or light. Chemically driven MNMs are composed of or contain certain reactive material(s) that convert chemical energy of a fuel into kinetic energy (motion) of the particles. Several different materials have been explored over the last decade for the preparation of a wide variety of MNMs. Here, the discovery of materials and approaches to enhance the efficiency of chemically driven MNMs are reviewed. Several prominent applications of the MNMs, especially in the fields of biomedicine and environmental science, are also discussed, as well as the limitations of existing materials and future research directions.
Inspired by the machines that have changed the world through their autonomous functions, scientists have focused their attention on performing similar functions at the micro/nanoscale. The motility of these micro/nanomachines (micro/nanomotors) offers enormous opportunities for cargo delivery, biodetection, and environmental and biomedical applications. Among the various geometries of micro/nanomotors, a tubular shape provides asymmetric inner and outer surfaces, where the inner wall hosts chemical reactions that supply the moving power and the outer wall can be modified for specific chemical and biological functions. This review describes the concept of tubular micro/nanomotors, including their basic principles, fabrication methods and control over their motion. With the assistance of catalytic reactions, tubular micro/nanomotors can generate a powerful thrust force to navigate in complex natural and in vitro environments. Modification of the tubular micro/nanomotors allows the motors to capture, transport, and release selected cargos on demand. In addition, their application in sensing and decontamination benefits from their collection behavior and self-mixing effect. Furthermore, noncatalytic reaction-driven tubular micro/nanomotors, such as redox-based and biohybrid tubular micro/nanomotors, provide new possibilities for practical in vivo applications. The state-of-the-art tubular micro/nanomotors could offer a promising platform for various applications, e.g., lab-on-chip devices and in vivo theranostics.
