Magnetically Driven Micro and Nanorobots

Manipulation and navigation of micro and nanoswimmers in different fluid environments can be achieved by chemicals, external fields, or even motile cells. Many researchers have selected magnetic fields as the active external actuation source based on the advantageous features of this actuation strategy such as remote and spatiotemporal control, fuel-free, high degree of reconfigurability, programmability, recyclability, and versatility. This review introduces fundamental concepts and advantages of magnetic micro/nanorobots (termed here as "MagRobots") as well as basic knowledge of magnetic fields and magnetic materials, setups for magnetic manipulation, magnetic field configurations, and symmetry-breaking strategies for effective movement. These concepts are discussed to describe the interactions between micro/nanorobots and magnetic fields. Actuation mechanisms of flagella-inspired MagRobots (i.e., corkscrew-like motion and traveling-wave locomotion/ciliary stroke motion) and surface walkers (i.e., surface-assisted motion), applications of magnetic fields in other propulsion approaches, and magnetic stimulation of micro/nanorobots beyond motion are provided followed by fabrication techniques for (quasi)spherical, helical, flexible, wire-like, and biohybrid MagRobots. Applications of MagRobots in targeted drug/gene delivery, cell manipulation, minimally invasive surgery, biopsy, biofilm disruption/eradication, imaging-guided delivery/therapy/surgery, pollution removal for environmental remediation, and (bio)sensing are also reviewed. Finally, current challenges and future perspectives for the development of magnetically powered miniaturized motors are discussed

Real-Time Gait Phase Detection on Wearable Devices for Real-World Free-Living Gait

Detecting gait phases with wearables unobtrusively and reliably in real-time is important for clinical gait rehabilitation and early diagnosis of neurological diseases. Due to hardware limitations of microcontrollers in wearable devices (e.g., memory and computation power), reliable real-time gait phase detection on the microcontrollers remains a challenge, especially for long-term real-world free-living gait. In this work, a novel algorithm based on a reduced support vector machine (RSVM) and a finite state machine (FSM) is developed to address this. The RSVM is developed by exploiting the cascaded K-means clustering to reduce the model size and computation time of a standard SVM by 88% and a factor of 36, with only minor degradation in gait phase prediction accuracy of around 4%. For each gait phase prediction from the RSVM, the FSM is designed to validate the prediction and correct misclassifications. The developed algorithm is implemented on a microcontroller of a wearable device and its real-time (on the fly) classification performance is evaluated by twenty healthy subjects walking along a predefined real-world route with uncontrolled free-living gait. It shows a promising real-time performance with an accuracy of 91.51%, a sensitivity of 91.70%, and a specificity of 95.77%. The algorithm also demonstrates its robustness with varying walking conditions

Riociguat treatment in patients with chronic thromboembolic pulmonary hypertension: Final safety data from the EXPERT registry

Objective: The soluble guanylate cyclase stimulator riociguat is approved for the treatment of adult patients with pulmonary arterial hypertension (PAH) and inoperable or persistent/recurrent chronic thromboembolic pulmonary hypertension (CTEPH) following Phase

Atomic force microscope integrated with a multiple degrees-of-freedom magnetic actuator

The present invention relates to a biomolecular measurement system (1), which enables to measure the intermolecular forces arising from the interaction between two biomolecules or the intramolecular forces within a single biomolecule by using an atomic force microscope (AFM). In the present invention, the cantilever (2) is moved only when the actuator (4) moves the magnetic nanowire (3) and thus moves the molecule attached to the end of the magnetic nanowire (3). Since the cantilever (2) is not moved, fluctuation and disturbance is not created in the liquid containing the biomolecules. Thus, the measurements are made more accurately and with higher resolution. Additionally, by means of the actuator (4), the biomolecules are enabled to be moved upon exertion of magnetic force at any coordinate on x, y and z axes on the nanowire (3), or exertion of torque on two axes

Self-folding mobile microrobots for biomedical applications

The presented microrobotic platform combines the advantages of self-folding NIR light sensitive polymer bilayers, magnetic alginate microbeads, and a 3D manipulation system and introduces a solution for targeted, on-demand drug and cell delivery. First feasibility studies are presented together with the potential of the full design

Magnetic microrobots with addressable shape control

Shape shifting soft microrobots are generated from self-folding hydrogel bilayer structures. The folding conditions are analyzed to develop an optimal strategy for producing desired three-dimensional shapes. We present two different methods for programming magnetization in these microrobots that are variant and invariant to folding. The microrobots can be navigated through user-defined trajectories using rotating magnetic fields, and the morphing in response to temperature changes can be tuned for adaptive behavior. On-demand modulation of the mobility of individual microrobots is demonstrated by morphing their shape using selective near infrared light (NIR) exposure

Functional polypyrrole coatings for wirelessly controlled magnetic microrobots

A wirelessly controlled magnetic microrobot has been proposed to diagnose and treat pathologies in the posterior segment of the human eye. The robot consists of a magnetic CoNi platform with a conformal coating of functional polymers. Electrodeposition has been the preferred method to fabricate and to functionalize the microrobot. Poly(pyrrole), a widely studied intrinsically conductive polymer has been investigated as a biocompatible coating to reduce biofouling, and as a coating that can release incorporated drugs on demand. The mechanism of redox cycling has been investigated to reduce the stiction of NIH 3T3 fibroblasts onto poly(pyrrole) surfaces. To demonstrate triggered drug release, Rhodamine B has been incorporated into the Ppy matrix as a model drug. Rapid Rhodamine B release is obtained when eddy current losses are induced by alternating magnetic fields on the CoNi substrates underneath these films

Fabrication of Segmented Au/Co/Au Nanowires: Insights in the Quality of Co/Au Junctions

Electrodeposition is a versatile method, which enables the fabrication of a variety of wire-like nanoarchitectures such as nanowires, nanorods, and nanotubes. By means of template-assisted electrodeposition, segmented Au/Co/Au nanowires are grown in anodic aluminum oxide templates from two different electrolytes. To tailor the properties of the cobalt segments, several electrochemical conditions are studied as a function of current density, pulse deposition, and pH. The morphology, crystal structure, and magnetic properties are accordingly investigated. Changes in the deposition conditions affect the cobalt electrocrystallization process directly. Cobalt tends to crystallize mainly in the hexagonal close-packed structure, which is the reason cobalt might not accommodate satisfactorily on the face-centered cubic Au surface or vice versa. We demonstrate that by modifying the electrolyte and the applied current densities, changes in the texture and the crystalline structure of cobalt lead to a good quality connection between dissimilar segments. In particular, lowering the bath pH, or using pulse plating at a high overpotential, produces polycrystalline fcc Co and thus well-connected Co/Au bimetallic junctions with smooth interface. These are crucial factors to be carefully considered taking into account that nanowires are potential building blocks in micro- and nanoelectromechanical systems. © 2014 American Chemical Society.1

Magnetoelectric micromachines with wirelessly controlled navigation and functionality

The use of a single energy source for both manipulating micromachines and triggering their functionalities will result in highly integrated devices and simplify the design of the controlling platform. Here, we demonstrate this concept employing magnetoelectric Janus particle-based micromachines, which are fabricated by coating SiO2 microspheres with a CoFe2O4–BaTiO3 bilayer composite. While the inner magnetic CoFe2O4 layer enables the micromachines to be maneuvered using low magnitude rotating magnetic fields, the magnetoelectric bilayer composite provides the ability to remotely generate electric charges upon the application of a time-varying magnetic field. To demonstrate the capabilities of these micromachines, noble metals such as Au, Ag and Pt are magnetoelectrochemically reduced from their corresponding precursor salts and form nanoparticles on the surface of the micromachines. Magnetoelectric micromachines are promising devices for their use as metal scavengers, cell stimulators and electric field-assisted drug delivery agents