Ferromagnetic nanowires are finding use as untethered sensors and actuators for probing micro‐ and nanoscale biophysical phenomena, such as for localized sensing and application of forces and torques ...on biological samples, for tissue heating through magnetic hyperthermia, and for microrheology. Quantifying the magnetic properties of individual isolated nanowires is crucial for such applications. Dynamic cantilever magnetometry is used to measure the magnetic properties of individual sub‐500 nm diameter polycrystalline nanowires of Ni and Ni80Co20 fabricated by template‐assisted electrochemical deposition. The values are compared with bulk, ensemble measurements when the nanowires are still embedded within their growth matrix. It is found that single‐particle and ensemble measurements of nanowires yield significantly different results that reflect inter‐nanowire interactions and chemical modifications of the sample during the release process from the growth matrix. The results highlight the importance of performing single‐particle characterization for objects that will be used as individual magnetic nanoactuators or nanosensors in biomedical applications.
Dynamic cantilever magnetometry is used to measure the magnetic properties of individual polycrystalline Ni and Ni80Co20 nanowires fabricated by template‐assisted electrochemical deposition. Single nanowire measurements reveal significant differences from typical bulk ensemble measurements and pave the way for the use of these nanowires as quantitative sensors and actuators for probing micro‐ and nanoscale biophysical phenomena.
The last decade has seen a surge of interest in the field of catalytically propelled micro‐ and nanoswimmers for their potential use in biomedical applications, such as biosensing, biopsy, targeted ...drug delivery, and on‐the‐fly chemistry. However, to fully utilize these devices, precise control over their motion is essential. Therefore, it is important to thoroughly understand their locomotion mechanisms. Herein, the currently accepted mechanisms for propulsion are discussed, which are self‐electrophoresis, self‐diffusiophoresis, and bubble recoil. Additionally, the concept of using multilocomotive mechanisms as a solution to achieve fully autonomous navigation is explored. Moreover, recent advances in the design of these devices are explored.
Chemically driven micromotors display unpredictable trajectories due to the rotational Brownian motion interacting with the surrounding fluid molecules. This hampers the practical applications of ...these tiny robots, particularly where precise control is a requisite. To overcome the rotational Brownian motion and increase motion directionality, robots are often decorated with a magnetic composition and guided by an external magnetic field. However, despite the straightforward method, explicit analysis and modeling of their motion have been limited. Here, catalytic Janus micromotors are fabricated with distinct magnetizations and a controlled self‐propelled motion with magnetic steering is shown. To analyze their dynamic behavior, a dynamic model that can successfully predict the trajectory of micromotors in uniform viscous flows in real time by incorporating a form of state‐dependent‐coefficient with a robust two‐stage Kalman filter is theoretically developed. A good agreement is observed between the theoretically predicted dynamics and experimental observations over a wide range of model parameter variations. The developed model can be universally adopted to various designs of catalytic micro‐/nanomotors with different sizes, geometries, and materials, even in diverse fuel solutions. Finally, the proposed model can be used as a platform for biosensing, detecting fuel concentration, or determining small‐scale motors’ propulsion mechanisms in an unknown environment.
A dynamic model is reported to predict navigation trajectories in real time for magnetically driven chemically propelled Janus micromotors with distinctive magnetic anisotropies and propulsion mechanisms including self‐diffusiophoresis and bubble‐recoil. The developed model can work as a biosensor for measuring fuel concentration and determining micromotors’ propulsion mechanism in unknown environments.
Micro‐ and nanorobots have shown great potential for applications in various fields, including minimally invasive surgery, targeted therapy, cell manipulation, environmental monitoring, and water ...remediation. Recent progress in the design, fabrication, and operation of these miniaturized devices has greatly enhanced their versatility. In this report, the most recent progress on the manipulation of small‐scale robots based on power sources, such as magnetic fields, light, acoustic waves, electric fields, thermal energy, or combinations of these, is surveyed. The design and propulsion mechanism of micro‐ and nanorobots are the focus of this article. Their fabrication and applications are also briefly discussed.
Externally powered micro‐ and nanorobots are promising candidates for future biomedical applications. Recent progress on externally powered small‐scale robots is summarized based on their power sources. The emphasis is laid on the design and propulsion mechanism of the microrobots. The fabrication and application is briefly discussed as well.
3D Fabrication of Fully Iron Magnetic Microrobots Alcântara, Carlos C. J.; Kim, Sangwon; Lee, Sunkey ...
Small (Weinheim an der Bergstrasse, Germany),
04/2019, Letnik:
15, Številka:
16
Journal Article
Recenzirano
Odprti dostop
Biocompatibility and high responsiveness to magnetic fields are fundamental requisites to translate magnetic small‐scale robots into clinical applications. The magnetic element iron exhibits the ...highest saturation magnetization and magnetic susceptibility while exhibiting excellent biocompatibility characteristics. Here, a process to reliably fabricate iron microrobots by means of template‐assisted electrodeposition in 3D‐printed micromolds is presented. The 3D molds are fabricated using a modified two‐photon absorption configuration, which overcomes previous limitations such as the use of transparent substrates, low writing speeds, and limited depth of field. By optimizing the geometrical parameters of the 3D molds, metallic structures with complex features can be fabricated. Fe microrollers and microswimmers are realized that demonstrate motion at ≈20 body lengths per second, perform 3D motion in viscous environments, and overcome higher flow velocities than those of “conventional 3D printed helical microswimmers.” The cytotoxicity of these microrobots is assessed by culturing them with human colorectal cancer (HCT116) cells for four days, demonstrating their good biocompatibility characteristics. Finally, preliminary results regarding the degradation of iron structures in simulated gastric acid liquid are provided.
Biocompatible and degradable Fe microrobots with enhanced magnetic volume are fabricated by 3D template‐assisted deposition. Microhelices are able to execute 3D motion in viscous fluids and outperform metal‐coated polymer structures in upstream motion measurements inside microfluidic channels. Furthermore, microrollers are able to move at 500 µm s−1, about 20 body lengths per second, under low intensity magnetic fields.
The field of small‐scale robotics is undergoing a paradigm shift toward the use of soft smart materials. The integration of soft smart components in micro‐ and nanorobotic platforms not only allows ...for more sophisticated locomotion mechanisms, but also more closely mimicks the functioning of biological systems. A soft hybrid nanorobot that mimics an electric eel, a knifefish with an elongated cylindrical body that is able to generate electricity during its motion, is presented here. These nanoeels consist of a flexible piezoelectric tail composed of a polyvinylidene fluoride–based copolymer, linked to a polypyrrole nanowire, which is decorated with nickel rings for magnetic actuation. Upon the application of rotating magnetic fields, the piezoelectric soft tail is deformed causing changes in its electric polarization. Capitalizing on this magnetically coupled piezoelectric effect, electrostatically enhanced on‐demand release of therapeutic cargo loaded on the surface of the piezoelectric tail is demonstrated. It is also shown that this approach allows for a pulsatile release of payloads. Interestingly, the driving magnetic parameters can be selected to provide the nanoeel with translational motion or to control the discharge kinetics of the drug.
Eel‐inspired soft nanorobots (nanoeels) are fabricated by combining magnetic segments with a flexible piezoelectric tail. Under the swimming mode, drug‐functionalized nanoeels are magnetically guided to target locations with minimal drug release. Once at target locations, magnetic fields are switched to activate the drug release mode to wirelessly deliver drugs on demand.
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