Bacteria‐inspired magnetic helical micro‐/nanoswimmers can be actuated and steered in a fuel‐free manner using a low‐strength rotating magnetic field, generating remotely controlled 3D locomotion with high precision in a variety of biofluidic environments. They are therefore envisioned for biomedical applications related to targeted diagnosis and therapy. In this article, a porous hollow microswimmer possessing an outer shell aggregated by mesoporous spindle‐like magnetite nanoparticles (NPs) and a helical‐shaped inner cavity is proposed. The fabrication is straightforward via a cost‐effective mass‐production process of biotemplated synthesis using helical microorganisms. Here, Spirulina‐based fabrication is demonstrated as an example. The fabricated microswimmers are superparamagnetic and exhibit low cytotoxicity. They are also capable of performing structural disassembly to form individual NPs using ultrasound when needed. For the first time in the literature of helical microswimmers, a porous hollow architecture is successfully constructed, achieving an ultrahigh specific surface area for surface functionalization and enabling diffusion‐based cargo loading/release. Furthermore, experimental and analytical results indicate better swimming performance of the microswimmers than the existing non‐hollow helical micromachines of comparable sizes and dimensions. These characteristics of the as‐proposed microswimmers suggest a novel microrobotic tool with high loading capacity for targeted delivery of therapeutic/imaging agents in vitro and in vivo.

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.

Abstract-This paper deals with the benefits of using a nonlinear model-based approach for controlling magnetically guided therapeutic microrobots in the cardiovascular system. Such robots used for minimally invasive interventions consist of a polymer binded aggregate of nanosized ferromagnetic particles functionalized by drug-conjugated micelles. The proposed modeling addresses wall effects (blood velocity in minor and major vessels' bifurcations, pulsatile blood flow and vessel walls, and effect of robot-to-vessel diameter ratio), wall interactions (contact, van der Waals, electrostatic and steric forces), nonNewtonian behaviour of blood and different driving designs as well. Despite nonlinear and thorough, the resulting model can both be exploited to improve the targeting ability and be controlled in closed-loop using nonlinear control theory tools. In particular, we infer from the model an optimization of both the designs and the reference trajectory to minimize the control efforts. Efficiency and robustness to noise and model parameter's uncertainties are then illustrated through simulations results for a bead pulled robot of radius 250µm in a small artery.Index Terms-Endovascular navigation, magnetic steering, nonlinear modeling, optimal trajectory, nonlinear controller and observer.

The last decade has seen the rapid development of untethered mobile micro‐ and nanorobots able to navigate liquids by means of external power sources or by harvesting chemicals from their surrounding media. These tiny devices hold great promise for applications in the biomedical field including targeted drug delivery, localized diagnostics, microsurgery, and cell stimulation. However, to translate small‐scale robots from the laboratory to the clinic, many challenges remain. A major obstacle is the lack of imaging technologies that will allow for precise tracking of the devices in vivo. Here, the current progress, challenges, and future possibilities in the monitoring and tracking of biomedical micro‐ and nanomachines using established as well as less conventional imaging technologies are reviewed.

International audienceElectrostatically actuated nanoelectromechanical switches based on intershell displacement mechanisms within batch fabricated, bidirectional multiwalled carbon nanotube MWNT bearings are reported. Multiple devices with a 220 nm pitch are constructed within individual MWNT supermolecules. Experimental results on performance metrics including low switching voltages 0.8 to 6 V, repeatability, hysteresis, and failure modes are presented

We report an experimental and theoretical investigation into mass transport between individual carbon nanotubes (CNTs) via their central cores. These CNT fluidic junctions can serve as basic elements for more complex nanofluidic systems and can also provide a structure for testing theories of fluid flow at the nanoscale. Controlled melting, evaporation, and flowing of copper and tin within and between nanotube shells are investigated experimentally. Cap-to-wall and wall-to-cap mass flow are realized by electric current driven heating, diffusion, and electromigration under low bias voltages between 1.5 and 1.8 V. A comparison shows that the mass loss for the cap-to-wall architecture is much smaller than that for the wall-to-cap junction. A molecular dynamics simulation is presented that provides further insight into the transport mechanism.

International audienceThis review presents the state of the art of magnetic resonance imaging(MRI)-guided nanorobotic systems that can perform diagnostic, curative,and reconstructive treatments in the human body at the cellular and subcellular levels in a controllable manner. The concept of an MRI-guided nanorobotic system is based on the use of an MRI scanner to induce the required external driving forces to propel magnetic nanocapsules to a specific target. It is an active targeting mechanism that provides simultaneous propulsion and imaging capabilities, which allow the implementation of real-time feedback control of the targeting process. The architecture of the system comprises four main modules: (a) the nanocapsules, (b) the MRI propulsion module, (c) theMRI trackingmodule (for image processing), and (d ) the controller module. A key concept is the nanocapsule technology, which is based on carriers such as liposomes, polymermicelles, gold nanoparticles, quantum dots, metallic nanoshells, and carbon nanotubes. Descriptions of the significant challenges faced by theMRI-guided nanorobotic system are presented, and promising solutions proposed by the involved research community are discussed. Emphasis is placed on reviewing the limitations imposed by the scaling effects that dominate within the blood vessels and also on reviewing the control algorithms and computational tools that have been developed for real-time propulsion and tracking of the nanocapsules

We report the partial core-shell nanowire motors. These nanowires are fabricated using our previously developed electrodeposition-based technique, and their catalytic locomotion in the presence of H2O2 is investigated. Unlike conventional bimetallic nanowires that are selfelectroosmotically propelled, our Au/Ru core-shell nanowires show both a noticeable decrease in rotational diffusivity and increase in motor speed with nanowire length. Numerical modelling based on self-electroosmosis attributes the decreases in rotational diffusivity to the formation of toroidal vortices at the nanowire tail, but fails to explain the speed increase with length. To reconcile this inconsistency, we propose a combined mechanism of self-diffusiophoresis and