After the tremendous advances over the past two decades, micro‐/nanorobots can effectively convert other forms of energy into propulsion and movement, as well as be navigated to targeted locations ...under physiological conditions and environments. They have been demonstrated to have the potential to load, transport, and deliver therapeutic payloads directly to disease sites, thereby improving the therapeutic efficacy and reducing systemic side effects of highly toxic drugs. In this feature article, the various propulsion modalities of micro‐/nanorobots ranging from chemical/biochemical reactions to external fields, and to motile microorganisms are summarized and commented in terms of driving forces required by the automotive motion in biological media, biocompatibility, as well as the corresponding advantages and limitations in terms of biomedical applications. Then, the latest developments of in vitro and in vivo active drug delivery based on micro‐/nanorobots are discussed in detail. The challenges and future prospects are also highlighted in the end. With ever booming research enthusiasm in this field and increasing multidisciplinary cooperation, micro‐/nanorobots with intelligence and multifunctions will emerge in the near future, which would have a profound impact on the treatment of diseases.
An overview of recent developments of active drug delivery based on micro‐/nanorobots has been presented. With continuous innovation, future micro‐/nanorobots with intelligence and multifunctionality will represent an important modality within diverse biomedical applications, providing unlimited opportunities beyond one's imagination.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Light, as an external stimulus, is capable of driving the motion of micro/nanomotors (MNMs) with the advantages of reversible, wireless and remote manoeuvre on demand with excellent spatial and ...temporal resolution. This review focuses on the state-of-the-art light-driven MNMs, which are able to move in liquids or on a substrate surface by converting light energy into mechanical work. The general design strategies for constructing asymmetric fields around light-driven MNMs to propel themselves are introduced as well as the photoactive materials for light-driven MNMs, including photocatalytic materials, photothermal materials and photochromic materials. Then, the propulsion mechanisms and motion behaviors of the so far developed light-driven MNMs are illustrated in detail involving light-induced phoretic propulsion, bubble recoil and interfacial tension gradient, followed by recent progress in the light-driven movement of liquid crystalline elastomers based on light-induced deformation. An outlook is further presented on the future development of light-driven MNMs towards overcoming key challenges after summarizing the potential applications in biomedical, environmental and micro/nanoengineering fields.
This review summarizes the recent advances in light-driven micro/nanomotors and highlights the challenges and perspectives toward environmental, biomedical and micro/nanoengineering applications.
The new capabilities and functionalities of synthetic micro/nanomotors open up considerable opportunities for diverse environmental and biomedical applications. Water‐powered micromachines are ...particularly attractive for realizing many of these applications. Magnesium‐based motors directly use water as fuel to generate hydrogen bubbles for their propulsion, eliminating the requirement of common toxic fuels. This Review highlights the development of new Mg‐based micromotors and discusses the chemistry that makes it extremely attractive for micromotor applications. Understanding these Mg properties and its transient nature is essential for controlling the propulsion efficiency, lifetime, and overall performance. The unique and attractive behavior of Mg offers significant advantages, including efficient water‐powered movement, remarkable biocompatibility, controlled degradation, convenient functionalization, and built‐in acid neutralization ability, and has paved the way for multifunctional micromachines for diverse real‐life applications, including operation in living animals. A wide range of such Mg motor‐based applications, including the detection and destruction of environmental threats, effective in‐vivo cargo delivery, and autonomous release, have been demonstrated. In conclusion, the current challenges, future opportunities, and performance improvements of the Mg‐based micromotors are discussed. With continuous innovation and attention to key challenges, it is expected that Mg‐based motors will have a profound impact on diverse biomedical and environmental applications.
This Review highlights the development of Mg‐based micromotors. The attractive behavior of Mg offers significant advantages for the operation of micromotors, including efficient water‐powered movement, biocompatibility, controlled degradation, convenient functionalization, and built‐in acid neutralization ability. The broad potential benefits that Mg‐based micro/nanomotors bring to the field of nanorobotics, along with existing challenges and future directions, are also discussed.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
This paper demonstrates a facile and low-cost carbothermal reduction preparation of monodisperse Fe3O4/C core–shell nanosheets (NSs) for greatly improved microwave absorption. In this protocol, the ...redox reaction between sheet-like hematite (α-Fe2O3) precursors and acetone under inert atmosphere and elevated temperature generates Fe3O4/C core–shell NSs with the morphology inheriting from α-Fe2O3. Thus, Fe3O4/C core–shell NSs of different sizes (a) and Fe3O4/C core–shell nanopolyhedrons are obtained by using different precursors. Benefited from the high crystallinity of the Fe3O4 core and the thin carbon layer, the resultant NSs exhibit high specific saturation magnetization larger than 82.51 emu·g–1. Simultaneously, the coercivity enhances with the increase of a, suggesting a strong shape anisotropy effect. Furthermore, because of the anisotropy structure and the complementary behavior between Fe3O4 and C, the as-obtained Fe3O4/C core–shell NSs exhibit strong natural magnetic resonance at a high frequency, enhanced interfacial polarization, and improved impedance matching, ensuring the enhancement of the microwave absorption. The 250 nm NSs–paraffin composites exhibit reflection loss (RL) lower than −20 dB (corresponding to 99% absorption) in a large frequency (f) range of 2.08–16.40 GHz with a minimum RL of −43.95 dB at f = 3.92 GHz when the thickness is tuned from 7.0 to 1.4 mm, indicating that the Fe3O4/C core–shell NSs are a good candidate to manufacture high-performance microwave absorbers. Moreover, the as-developed carbothermal reduction method could be applied for the fabrication of other composites based on ferrites and carbon.
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IJS, KILJ, NUK, PNG, UL, UM
Abstract
Metasurfaces have provided a promising approach to enhance the nonlinearity at subwavelength scale, but usually suffer from a narrow bandwidth as imposed by sharp resonant features. Here, we ...counterintuitively report a broadband, enhanced second-harmonic generation, in nanopatterned hyperbolic metamaterials. The nanopatterning allows the direct access of the mode with large momentum, rendering the rainbow light trapping, i.e. slow light in a broad frequency, and thus enhancing the local field intensity for boosted nonlinear light-matter interactions. For a proof-of-concept demonstration, we fabricated a nanostructured Au/ZnO multilayer, and enhanced second harmonic generation can be observed within the visible wavelength range (400-650 nm). The enhancement factor is over 50 within the wavelength range of 470-650 nm, and a maximum conversion efficiency of 1.13×10
−6
is obtained with a pump power of only 8.80 mW. Our results herein offer an effective and robust approach towards the broadband metasurface-based nonlinear devices for various important technologies.
Stretchable transparent conductors (STCs), generally consisting of conducting networks and stretchable transparent elastomers, can maintain stable conductivity and transparency even at large tensile ...strain, beyond the reach of rigid/flexible transparent conductors. They are essential components in stretchable/wearable electronics for using on irregular 3D conformable surfaces and have attracted tremendous attention in recent years. This review aims to provide systematical correlation of the conducting element–substrate interaction with the structural stability of conducting networks, as well as the properties and device applications of STCs. It starts with the micromechanics for stretching of conducting elements on substrates, including the mechanical mismatch, distribution/level of interfacial shear stress, and the deformation behavior of conducting elements on substrates. The macromechanics for stretching of conducting networks on substrates are then further illustrated from a more statistical point of view, namely sliding/preferred orientation of percolation networks, unfolding of buckled structures, and unit cell distortion/distributed rupture of nanomeshes. The structure‐dependent properties as well as the state‐of‐the‐art applications of STCs are summarized before ending with the conclusions and outlooks for STCs.
Stretchable transparent conductors (STCs) are key components of stretchable electronics. The conducting element–substrate interaction is systematically correlated with the structural stability of conducting networks, properties, and device applications of STCs. Special focus is put on the micromechanics of conducting elements on elastomers and the macromechanics of conducting networks. Conclusions and the outlook in this field are also presented.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Artificial self-propelled micromachines have shown great promise in biomedical sciences. In this work, we use Mg/Pt Janus micromotors with self-rejuvenating surfaces to enhance the electrochemical ...sensing performance and sensitivity toward glucose in human serum. The detection of glucose is based on the glucose oxidase enzyme and ferrocenemethanol shuttle system, where mass transfer was dramatically enhanced by the rapid motion of Mg/Pt Janus micromotors. The obtained chronoamperometric data show that Mg/Pt Janus micromotors play a synergistic role in enhancing the current response at millimolar concentrations of glucose in human serum. The current signals increased with the corresponding increase in amount of micromotors introduced. Furthermore, a linear relationship between current signal and glucose concentration was established, while the limit of detection improved when mobile Mg/Pt Janus micromachines were used. Glucose detection enhanced by micromachines may pave the way for their future applications in biomedicine and medical diagnostic devices.
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IJS, KILJ, NUK, PNG, UL, UM
In this work, we have demonstrated the autonomous motion of biologically-friendly Mg/Pt-Poly(N-isopropylacrylamide) (PNIPAM) Janus micromotors in simulated body fluids (SBF) or blood plasma without ...any other additives. The pit corrosion of chloride anions and the buffering effect of SBF or blood plasma in removing the Mg(OH)2 passivation layer play major roles for accelerating Mg–H2O reaction to produce hydrogen propulsion for the micromotors. Furthermore, the Mg/Pt-PNIPAM Janus micromotors can effectively uptake, transport, and temperature-control-release drug molecules by taking advantage of the partial surface-attached thermoresponsive PNIPAM hydrogel layers. The PNIPAM hydrogel layers on the micromotors can be easily replaced with other responsive polymers or antibodies by the surface modification strategy, suggesting that the as-proposed micromotors also hold a promising potential for separation and detection of heavy metal ions, toxicants, or proteins.
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IJS, KILJ, NUK, PNG, UL, UM
•Chemical sensing based on the motion of micro/nanorobots.•Electrochemical sensing with micro/nanorobots.•Fluorescent, electrochemiluminescent and colorimetric sensing with micro/nanorobots.•Motion ...enhanced mass transfer improves the detection response and sensitivity.
Synthetic micro- and nanorobots have attracted considerable attentions for their potential applications in environment, biomedicine and microengineering. In this review, we summarize the recent works on micro/nanorobots based sensing and biosensing according to different mechanisms: motion based sensing, electrochemical sensing with micro/nanorobots and fluorescent, electrochemiluminescent, colorimetric sensing with micro/nanorobots. Micro/nanorobots offer a convenient and active detection for nucleic acid, protein, glucose, heavy metal ions, etc. in solution and surrounding atmosphere. Furthermore, the detection sensitivity and efficiency has been significantly improved due to the stirring in solution by the motion of micro/nanorobots.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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